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1

Search for Dark Matter  

E-Print Network (OSTI)

The search for dark matter is a very wide an active field of research, and I necessarily concentrate here only in some aspects of it. I will review the prospects for direct and indirect dark matter searches of Weakly Interacting Massive Particles in the dark halo of our galaxy and focus in particular on the data of GLAST, PAMELA and DAMA.

Graciela B. Gelmini

2008-10-21T23:59:59.000Z

2

The XENON Dark Matter Search  

SciTech Connect

The XENON experiment will search for Weakly Interacting Massive Particles (WIMPS), a leading candidate for the dark matter content of the Universe. The XENON detector uses the simultaneous measurement of ionization and scintillation in liquid xenon to distinguish between nuclear recoils and background electronic interactions. Ionization electrons are extracted into the xenon vapor where they produce a large proportional scintillation signal in a grid assembly. Both prompt and proportional scintillation light are detected by PMT arrays on the top and bottom of the active liquid xenon volume. The distribution of proportional scintillation light in the top PMT array can be used to achieve xy position resolution, while the ionization drift time gives position resolution in the z direction. This allows the definition of a low-background fiducial volume. I describe the results of the R and D phase of this project before providing a status update on the XENON10 phase.

McKinsey, D. N. [Department of Physics, Yale University, New Haven, Connecticut 06520 (United States)

2006-11-17T23:59:59.000Z

3

Direct search for WIMP dark matter  

E-Print Network (OSTI)

We will review the experimental aspects of the direct search for WIMP dark matter. In thin search, one looks in a terrestrial target for nuclear recoils produced by the impacts with WIMPs from the galatic halo. After describing the different search strategies and review the currently running experiments and the prospects of future experiments

J. Gascon

2005-04-11T23:59:59.000Z

4

PICO-LON project to search for cosmic dark matter  

Science Conference Proceedings (OSTI)

The dark matter search project PICO-LON has been started. Thin and wide area NaI(Tl) scintillator is the promising detector system to study the properties of dark matter particle.

Fushimi, K.; Harada, K.; Kameda, Y.; Nakayama, S. [Department of Physics, University of Tokushima, 1-1 Minami Josanjimacho Tokushima city, 770-8502 Tokushima (Japan); Ejiri, H.; Shima, T. [Research Center for Nuclear Physics, Osaka University, 10-1 Mihogaoka Ibaraki city, 567-0047 Osaka (Japan); Hazama, R. [Department of Engineering, Hiroshima University, 1-4-1 Higashi Kagamiyama Higashi Hiroshima city, 739-8527 Hiroshima (Japan); Imagawa, K.; Matsumoto, E. [Horiba Ltd., 2 Minami-ku Kisshoin Miyanohigashimachi Kyoto city, 601-8510 Kyoto (Japan)

2010-08-12T23:59:59.000Z

5

The Universe Adventure - The Search for Dark Matter  

NLE Websites -- All DOE Office Websites (Extended Search)

Search for Dark Matter Search for Dark Matter Large Hadron Collider Particle accelerators, such as the newly constructed LHC (Large Hadron Collider) at CERN in Geneva, Switzerland, use powerful magnets to accelerate particles to velocities near that of light and collide them into target beams. Physicists analyze the spray of particles created by the collisions which may contain clues about the properties of elusive dark matter particles. Today the search for dark matter is carried out in labs, observatories, and particle accelerators around the world. Scientists hope that the next generation of experiments will finally uncover the identity of dark matter. Alternatives to Dark Matter Some cosmologists are looking for alternative theories that explain these phenomena without relying on unobservable dark matter. Most of these

6

Search for Low-Mass Dark Matter at BABAR  

E-Print Network (OSTI)

This review briefly describes light dark matter searches performed by the BABAR experiment. Although dark matter candidates have traditionally been associated with heavy particles appearing in extensions of the Standard Model, a lighter component remains a well motivated alternative, and many scenarios of light dark matter have been recently proposed. Thanks to their large luminosities, B factories offer an ideal environment to probe these possibilities, complementing searches from direct detection and satellite experiments.

Echenard, B

2012-01-01T23:59:59.000Z

7

Indirect Search for Dark Matter with the ANTARES Neutrino Telescope  

Science Conference Proceedings (OSTI)

One of the goals of the ANTARES underwater neutrino telescope is the search for dark matter in the universe. In this paper the first results on the search for dark matter in the Sun with ANTARES in its 5 line configuration, as well as sensitivity studies with the full ANTARES detector are presented.

Loucatos, S. [IRFU-SPP, CEA-Saclay, 91191 Gif sur Yvette (France)

2010-02-10T23:59:59.000Z

8

Search for Dark Matter Satellites of the Milky Way with the Fermi LAT  

E-Print Network (OSTI)

Results and discussion 4.1 Search for Dark Matter SatellitesNeutrino Ob- servatory IV: Searches for Dark Matter andFermi-LAT Collaboration], Search for Dark Matter Satellites

Zalewski, Sheridan Henryk

2013-01-01T23:59:59.000Z

9

Search for Dark Matter Satellites Using the FERMI-LAT  

SciTech Connect

Numerical simulations based on the {Lambda}CDM model of cosmology predict a large number of as yet unobserved Galactic dark matter satellites. We report the results of a Large Area Telescope (LAT) search for these satellites via the {gamma}-ray emission expected from the annihilation of weakly interacting massive particle (WIMP) dark matter. Some dark matter satellites are expected to have hard {gamma}-ray spectra, finite angular extents, and a lack of counterparts at other wavelengths. We sought to identify LAT sources with these characteristics, focusing on {gamma}-ray spectra consistent with WIMP annihilation through the b{bar b} channel. We found no viable dark matter satellite candidates using one year of data, and we present a framework for interpreting this result in the context of numerical simulations to constrain the velocity-averaged annihilation cross section for a conventional 100 GeV WIMP annihilating through the b{bar b} channel.

Ackermann, M.; /DESY; Albert, A.; /Ohio State U.; Baldini, L.; /INFN, Pisa; Ballet, J.; /DAPNIA, Saclay; Barbiellini, G.; /INFN, Trieste /Trieste U.; Bastieri, D.; /INFN, Padua /Padua U.; Bechtol, K.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bellazzini, R.; /INFN, Pisa; Blandford, R.D.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bloom, E.D.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /SLAC; Bonamente, E.; /INFN, Perugia /Perugia U.; Borgland, A.W.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bottacini, E.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Brandt, T.J.; /IRAP, Toulouse /Toulouse III U.; Bregeon, J.; /INFN, Pisa; Brigida, M.; /Bari U. /INFN, Bari; Bruel, P.; /Ecole Polytechnique; Buehler, R.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Burnett, T.H.; /Washington U., Seattle; Caliandro, G.A.; /ICE, Bellaterra; Cameron, R.A.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /IASF, Milan /IASF, Milan /DAPNIA, Saclay /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /ASDC, Frascati /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Montpellier U. /Stockholm U. /Stockholm U., OKC /ASDC, Frascati /Bari U. /INFN, Bari /Naval Research Lab, Wash., D.C. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Montpellier U. /Bari U. /INFN, Bari /Ecole Polytechnique /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Hiroshima U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Bari U. /INFN, Bari /INFN, Bari /INFN, Perugia /Perugia U. /Bari U. /INFN, Bari /Bari U. /INFN, Bari /Bologna Observ. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; /more authors..

2012-08-16T23:59:59.000Z

10

Dark matter searches with cosmic antideuterons: status and perspectives  

E-Print Network (OSTI)

The search for antideuterons in cosmic rays has been proposed as a promising channel for dark matter indirect detection, especially for dark matter particles with a low or intermediate mass. With the current operational phase of the AMS-02 experiment and the ongoing development of a future dedicated experiment, the General Antiparticle Spectrometer (GAPS), there are exciting prospects for a dark matter detection in the near future. In this paper we develop a detailed and complete re-analysis of the cosmic-ray antideuteron signal, by discussing the main relevant issues related to antideuteron production and propagation through the interstellar medium and the heliosphere. In particular, we first critically revisit the coalescence mechanism for antideuteron production in dark matter annihilation processes. Then, since antideuteron searches have their best prospects of detection at low kinetic energies where the effect of the solar wind and magnetic field are most relevant, we address the impact of solar modulation modeling on the antideuteron flux at the Earth by developing a full numerical 4D solution of cosmic rays transport in the heliosphere. We finally use these improved predictions to provide updated estimates of the reaching capabilities for AMS-02 and GAPS, compatible with the current constraints imposed by the antiprotons measurements of PAMELA. After the antiproton bound is applied, prospects of detection of up to about 15 events in GAPS LDB+ and AMS-02 missions are found, depending on the dark matter mass, annihilation rate and production channel from one side, and on the coalescence process, galactic and solar transport parameters on the other.

N. Fornengo; L. Maccione; A. Vittino

2013-06-18T23:59:59.000Z

11

The Cold Dark Matter Search test stand warm electronics card  

SciTech Connect

A card which does the signal processing for four SQUID amplifiers and two charge sensitive channels is described. The card performs the same functions as is presently done with two custom 9U x 280mm Eurocard modules, a commercial multi-channel VME digitizer, a PCI to GPIB interface, a PCI to VME interface and a custom built linear power supply. By integrating these functions onto a single card and using the power over Ethernet standard, the infrastructure requirements for instrumenting a Cold Dark Matter Search (CDMS) detector test stand are significantly reduced.

Hines, Bruce; /Colorado U., Denver; Hansen, Sten; /Fermilab; Huber, Martin; /Colorado U., Denver; Kiper, Terry; /Fermilab; Rau, Wolfgang; /Queen's U., Kingston; Saab, Tarek; /Florida U.; Seitz, Dennis; Sundqvist, Kyle; /UC, Berkeley; Mandic, Vuk; /Minnesota U.

2010-11-01T23:59:59.000Z

12

Commissioning Run of the CRESST-II Dark Matter Search  

E-Print Network (OSTI)

The CRESST cryogenic direct dark matter search at Gran Sasso, searching for WIMPs via nuclear recoil, has been upgraded to CRESST-II by several changes and improvements.We present the results of a commissioning run carried out in 2007. The basic element of CRESST-II is a detector module consisting of a large (~ 300 g) CaWO_4 crystal and a very sensitive smaller (~ 2 g) light detector to detect the scintillation light from the CaWO_4.Information from light-quenching factor studies allows the definition of a region of the energy-light yield plane which corresponds to tungsten recoils. A neutron test is reported which supports the principle of using the light yield to identify the recoiling nucleus. Data obtained with two detector modules for a total exposure of 48 kg-days are presented. Judging by the rate of events in the "all nuclear recoils" acceptance region the apparatus shows a factor ~ten improvement with respect to previous results, which we attribute principally to the presence of the neutron shield. In the "tungsten recoils" acceptance region three events are found, corresponding to a rate of 0.063 per kg-day. Standard assumptions on the dark matter flux, coherent or spin independent interactions,then yield a limit for WIMP-nucleon scattering of 4.8 \\times 10^{-7}pb, at M{WIMP} ~50 GeV.

G. Angloher; M. Bauer; I. Bavykina; A. Bento; A. Brown; C. Bucci; C. Ciemniak; C. Coppi; G. Deuter; F. von Feilitzsch; D. Hauff; S. Henry; P. Huff; J. Imber; S. Ingleby; C. Isaila; J. Jochum; M. Kiefer; M. Kimmerle; H. Kraus; J. -C. Lanfranchi; R. F. Lang; B. Majorovits; M. Malek; R. McGowan; V. B. Mikhailik; E. Pantic; F. Petricca; S. Pfister; W. Potzel; F. Proebst; W. Rau; S. Roth; K. Rottler; C. Sailer; K. Schaeffner; J. Schmaler; S. Scholl; W. Seidel; L. Stodolsky; A. J. B. Tolhurst; I. Usherov; W. Westphal

2008-09-10T23:59:59.000Z

13

The Search for Dark Matter in XENON100 using a Two-Dimensional Profile Likelihood Analysis  

E-Print Network (OSTI)

Detection and Collider Searches . . . . . . . . . . 2al. , “The LUX dark matter search,” J.Phys.Conf.Ser. , vol.latest LHC SUSY and Higgs searches and XENON100 data,” JCAP,

Lung, Kevin J.

2013-01-01T23:59:59.000Z

14

A Novel Antimatter Detector with Application to Dark Matter Searches  

Science Conference Proceedings (OSTI)

We report on recent accelerator testing of a prototype general antiparticle spectrometer (GAPS). GAPS uses a novel approach for indirect dark matter searches that exploits the antideuterons produced in neutralino-neutralino annihilations. GAPS captures these antideuterons into a target with the subsequent formation of exotic atoms. These exotic atoms decay with the emission of x-rays of precisely defined energy and a correlated pion signature from nuclear annihilation. This signature uniquely characterizes the antideuterons. Preliminary analysis of data from a prototype GAPS in an antiproton beam at the KEK accelerator in Japan has confirmed the multiple x-ray/pion star topology and indicated x-ray yields consistent with prior expectations. Moreover, our success in utilizing solid rather than gas targets represents a significant simplification over our original approach and offers potential gains in sensitivity through reduced dead mass in the target area.

Craig, W W; Fabris, L; Madden, N; Ziock, K; Hailey, C; Aramaki, T; Gabhauer, F; Koglin, J; Mori, K; Yu, H

2006-02-13T23:59:59.000Z

15

Neutrino Backgrounds to Dark Matter Searches and Directionality  

E-Print Network (OSTI)

Neutrino-nucleus coherent scattering cross sections can be as large as 10[superscript ?39] cm[superscript 2], while current dark matter experiments have sensitivities to WIMP coherent scattering cross sections several ...

Monroe, Jocelyn

16

CDF Note 10709 A Search For Dark Matter in the Monojet + Missing Transverse Energy  

E-Print Network (OSTI)

CDF Note 10709 A Search For Dark Matter in the Monojet + Missing Transverse Energy Signature in 6: November 23, 2011) We present the results of a search for dark matter production in the monojet + missing transverse energy signature. We analyze a sample of Tevatron pp collisions at s=1.96 TeV, recorded

Quigg, Chris

17

LIPSS Free-Electron Laser Searches for Dark Matter  

SciTech Connect

A variety of Dark Matter particle candidates have been hypothesized by physics Beyond the Standard Model (BSM) in the very light (10{sup -6} - 10{sup -3} eV) range. In the past decade several international groups have conducted laboratory experiments designed to either produce such particles or extend the boundaries in parameter space. The LIght Pseudo-scalar and Scalar Search (LIPSS) Collaboration, using the 'Light Shining through a Wall' (LSW) technique, passes the high average power photon beam from Jefferson Lab's Free-Electron Laser through a magnetic field upstream from a mirror and optical beam dump. Light Neutral Bosons (LNBs), generated by coupling of photons with the magnetic field, pass through the mirror ('the Wall') into an identical magnetic field where they revert to detectable photons by the same coupling process. While no evidence of LNBs was evident, new scalar coupling boundaries were established. New constraints were also determined for hypothetical para-photons and for millicharged fermions. We will describe our experimental setup and results for LNBs, para-photons, and milli-charged fermions. Plans for chameleon particle searches are underway.

Afanaciev, Andrei; Beard, Kevin; Biallas, George; Boyce, James R; Minarni, M; Ramdon, R; Robinson, Taylor; Shinn, Michelle D

2011-09-01T23:59:59.000Z

18

Quantifying galactic propagation uncertainty in WIMP dark matter search with AMS01 Z=-1 spectrum  

E-Print Network (OSTI)

A search for a WIMP dark matter annihilation signal is carried out in the AMS01 negatively charged (Z=-I) particle spectrum, following a set of supersymmetric benchmark scenarios in the mSUGRA framework. The result is ...

Xiao, Sa, Ph. D. Massachusetts Institute of Technology

2009-01-01T23:59:59.000Z

19

Nuclear spin structure in dark matter search: The finite momentum transfer limit  

E-Print Network (OSTI)

Spin-dependent elastic scattering of weakly interacting massive dark matter particles (WIMP) off nuclei is reviewed. All available, within different nuclear models, structure functions S(q) for finite momentum transfer (q>0) are presented. These functions describe the recoil energy dependence of the differential event rate due to the spin-dependent WIMP-nucleon interactions. This paper, together with the previous paper ``Nuclear spin structure in dark matter search: The zero momentum transfer limit'', completes our review of the nuclear spin structure calculations involved in the problem of direct dark matter search.

V. A. Bednyakov; F. Simkovic

2006-08-09T23:59:59.000Z

20

dark matter dark energy inflation  

E-Print Network (OSTI)

theory dark matter dark energy inflation The National Science Foundation The Kavli Foundation NSF Site Review November 28-29, 2005 #12;dark matter dark energy inflation NSF Site Visit ­ November 28 Gravitation initial conditions beyond single-field slow roll #12;dark matter dark energy inflation NSF Site

Hu, Wayne

Note: This page contains sample records for the topic "dark matter searches" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


21

The Search for Dark Matter with the Fermi Gamma Ray Space Telescope  

SciTech Connect

The Fermi Gamma-Ray Space Telescope has been scanning the gamma ray sky since it was launched by NASA in June 2008 and has a mission lifetime goal of 10 years. Largely due to our particle physics heritage, one of the main physics topics being studied by the Fermi LAT Collaboration is the search for dark matter via indirect detection. My talk will review the progress of these studies, something on how the LAT detector enables them, and expectations for the future. I will discuss both gamma-ray and (electron + positron) searches for dark matter, and some resulting theoretical implications.

Bloom, Elliott (SLAC)

2011-03-30T23:59:59.000Z

22

Can Solar Neutrinos be a Serious Background in Direct Dark Matter Searches?  

E-Print Network (OSTI)

The coherent contribution of all neutrons in neutrino nucleus scattering due to the neutral current is examined considering the boron solar neutrinos. These neutrinos could potentially become a source of background in the future dark matter searches aiming at nucleon cross sections in the region well below the few events per ton per year.

J. D. Vergados; H. Ejiri

2008-05-16T23:59:59.000Z

23

Search for a dark matter particle in high energy cosmic rays  

E-Print Network (OSTI)

Existing data hints that high energy cosmic ray experiments may offer the most promissing shot at finding a dark matter particle. A search in the PeV mass range is suggested, where the discovery of such a particle might help explain the GZK cutoff violation data.

Yukio Tomozawa

2008-04-09T23:59:59.000Z

24

Recent developments in the search for baryonic dark matter  

E-Print Network (OSTI)

Cosmological nucleosynthesis calculations imply that many of the baryons in the Universe must be dark. We discuss the likelihood that some of these dark baryons may reside in galaxies as Massive Compact Halo Objects (MACHOs), the remnants of a first generation of pregalactic or protogalactic stars. Various candidates have been proposed for such remnants and we review the many types of observations which can be used to detect or exclude them. Claims to have found positive evidence for some of the candidates have generally turned out to be spurious or questionable, so the status of the MACHO scenario remains controversial. However, it would be premature to reject MACHOs altogether and further observations are likely to resolve the issue soon.

B. J. Carr

2001-02-22T23:59:59.000Z

25

Dark Energy and Dark Matter  

E-Print Network (OSTI)

A brief overview of our current understanding of abundance and properties of dark energy and dark matter is presented. A more focused discussion of supersymmetric dark matter follows. Included is a frequentist approach to the supersymmetric parameter space and consequences for the direct detection of dark matter.

Keith A. Olive

2010-01-27T23:59:59.000Z

26

Matter Field, Dark Matter and Dark Energy  

E-Print Network (OSTI)

A model concerning particle theory and cosmology is proposed. Matter field, dark matter and dark energy are created by an energy flow from space to primordial matter fields at the phase transition in the early universe.

Masayasu Tsuge

2008-02-01T23:59:59.000Z

27

The PICASSO Dark Matter Experiment  

Science Conference Proceedings (OSTI)

The PICASSO experiment searches for cold dark matter through the direct detection of weakly interacting massive particles (WIMPs) via their spin?dependent interactions with fluorine at SNOLAB

Ubi Wichoski; The PICASSO Collaboration

2011-01-01T23:59:59.000Z

28

Search for dark matter annihilations in the Sun with the 79-string IceCube detector  

E-Print Network (OSTI)

We have performed a search for muon neutrinos from dark matter annihilation in the center of the Sun with the 79-string configuration of the IceCube neutrino telescope. For the first time, the DeepCore sub-array is included in the analysis, lowering the energy threshold and extending the search to the austral summer. The 317 days of data collected between June 2010 and May 2011 are consistent with the expected background from atmospheric muons and neutrinos. Upper limits are therefore set on the dark matter annihilation rate, with conversions to limits on spin-dependent and spin-independent WIMP-proton cross-sections for WIMP masses in the range 20 - 5000 GeV. These are the most stringent spin-dependent WIMP-proton cross-sections limits to date above 35 GeV.

IceCube collaboration; M. G. Aartsen; R. Abbasi; Y. Abdou; M. Ackermann; J. Adams; J. A. Aguilar; M. Ahlers; D. Altmann; K. Andeen; J. Auffenberg; X. Bai; M. Baker; S. W. Barwick; V. Baum; R. Bay; K. Beattie; J. J. Beatty; S. Bechet; J. Becker Tjus; K. -H. Becker; M. Bell; M. L. Benabderrahmane; S. BenZvi; J. Berdermann; P. Berghaus; D. Berley; E. Bernardini; D. Bertrand; D. Z. Besson; D. Bindig; M. Bissok; E. Blaufuss; J. Blumenthal; D. J. Boersma; S. Bohaichuk; C. Bohm; D. Bose1; S. Böser; O. Botner; L. Brayeur; A. M. Brown; R. Bruijn; J. Brunner; S. Buitink; M. Carson; J. Casey; M. Casier; D. Chirkin; B. Christy; K. Clark; F. Clevermann; S. Cohen; D. F. Cowen; A. H. Cruz Silva; M. Danninger; J. Daughhetee; J. C. Davis; C. De Clercq; S. De Ridder; F. Descamps; P. Desiati; G. de Vries-Uiterweerd; T. DeYoung; J. C. Díaz-Vélez; J. Dreyer; J. P. Dumm; M. Dunkman; R. Eagan; B. Eberhardt; J. Eisch; R. W. Ellsworth; O. Engdegĺrd; S. Euler; P. A. Evenson; O. Fadiran; A. R. Fazely; A. Fedynitch; J. Feintzeig; T. Feusels; K. Filimonov; C. Finley; T. Fischer-Wasels; S. Flis; A. Franckowiak; R. Franke; K. Frantzen; T. Fuchs; T. K. Gaisser; J. Gallagher; L. Gerhardt; L. Gladstone; T. Glüsenkamp; A. Goldschmidt; G. Golup; J. A. Goodman; D. Góra; D. Grant; A. Groß; S. Grullon; M. Gurtner; C. Ha; A. Haj Ismail; A. Hallgren; F. Halzen; K. Hanson; D. Heereman; P. Heimann; D. Heinen; K. Helbing; R. Hellauer; S. Hickford; G. C. Hill; K. D. Hoffman; R. Hoffmann; A. Homeier; K. Hoshina; W. Huelsnitz; P. O. Hulth; K. Hultqvist; S. Hussain; A. Ishihara; E. Jacobi; J. Jacobsen; G. S. Japaridze; O. Jlelati; A. Kappes; T. Karg; A. Karle; J. Kiryluk; F. Kislat; J. Kläs; S. R. Klein; J. -H. Köhne; G. Kohnen; H. Kolanoski; L. Köpke; C. Kopper; S. Kopper; D. J. Koskinen; M. Kowalski; M. Krasberg; G. Kroll; J. Kunnen; N. Kurahashi; T. Kuwabara; M. Labare; H. Landsman; M. J. Larson; R. Lauer; M. Lesiak-Bzdak; J. Lünemann; J. Madsen; R. Maruyama; K. Mase; H. S. Matis; F. McNally; K. Meagher; M. Merck; P. Mészáros; T. Meures; S. Miarecki; E. Middell; N. Milke; J. Miller; L. Mohrmann; T. Montaruli; R. Morse; R. Nahnhauer; U. Naumann; S. C. Nowicki; D. R. Nygren; A. Obertacke; S. Odrowski; A. Olivas; M. Olivo; A. O'Murchadha; S. Panknin; L. Paul; J. A. Pepper; C. Pérez de los Heros; D. Pieloth; N. Pirk; J. Posselt; P. B. Price; G. T. Przybylski; L. Rädel; K. Rawlins; P. Redl; E. Resconi; W. Rhode; M. Ribordy; M. Richman; B. Riedel; J. P. Rodrigues; C. Rott; T. Ruhe; B. Ruzybayev; D. Ryckbosch; S. M. Saba; T. Salameh; H. -G. Sander; M. Santander; S. Sarkar; K. Schatto; M. Scheel; F. Scheriau; T. Schmidt; M. Schmitz; S. Schoenen; S. Schöneberg; L. Schönherr; A. Schönwald; A. Schukraft; L. Schulte; O. Schulz; D. Seckel; S. H. Seo; Y. Sestayo; S. Seunarine; C. Sheremata; M. W. E. Smith; M. Soiron; D. Soldin; G. M. Spiczak; C. Spiering; M. Stamatikos; T. Stanev; A. Stasik; T. Stezelberger; R. G. Stokstad; A. Stöß; E. A. Strahler; R. Ström; G. W. Sullivan; H. Taavola; I. Taboada; A. Tamburro; S. Ter-Antonyan; S. Tilav; P. A. Toale; S. Toscano; M. Usner; D. van der Drift; N. van Eijndhoven; A. Van Overloop; J. van Santen; M. Vehring; M. Voge1; M. Vraeghe; C. Walck; T. Waldenmaier; M. Wallraff; M. Walter; R. Wasserman; Ch. Weaver; C. Wendt; S. Westerhoff; N. Whitehorn; K. Wiebe; C. H. Wiebusch; D. R. Williams; H. Wissing; M. Wolf; T. R. Wood; K. Woschnagg; C. Xu; D. L. Xu; X. W. Xu; J. P. Yanez; G. Yodh; S. Yoshida; P. Zarzhitsky; J. Ziemann; S. Zierke; A. Zilles; M. Zoll

2012-12-17T23:59:59.000Z

29

The Cryogenic Dark Matter Search and Background Rejection with Event Position Information  

SciTech Connect

Evidence from observational cosmology and astrophysics indicates that about one third of the universe is matter, but that the known baryonic matter only contributes to the universe at 4%. A large fraction of the universe is cold and non-baryonic matter, which has important role in the universe structure formation and its evolution. The leading candidate for the non-baryonic dark matter is Weakly Interacting Massive Particles (WIMPs), which naturally occurs in the supersymmetry theory in particle physics. The Cryogenic Dark Matter Search (CDMS) experiment is searching for evidence of a WIMP interaction off an atomic nucleus in crystals of Ge and Si by measuring simultaneously the phonon energy and ionization energy of the interaction in the CDMS detectors. The WIMP interaction energy is from a few keV to tens of keV with a rate less than 0.1 events/kg/day. To reach the goal of WIMP detection, the CDMS experiment has been conducted in the Soudan mine with an active muon veto and multistage passive background shields. The CDMS detectors have a low energy threshold and background rejection capabilities based on ionization yield. However, betas from contamination and other radioactive sources produce surface interactions, which have low ionization yield, comparable to that of bulk nuclear interactions. The low-ionization surface electron recoils must be removed in the WIMP search data analysis. An emphasis of this thesis is on developing the method of the surface-interaction rejection using location information of the interactions, phonon energy distributions and phonon timing parameters. The result of the CDMS Soudan run118 92.3 live day WIMP search data analysis is presented, and represents the most sensitive search yet performed.

Wang, Gen-sheng; /Case Western Reserve U.

2005-01-01T23:59:59.000Z

30

First Results from the Cryogenic Dark Matter Search Experiment at the Deep Site  

Science Conference Proceedings (OSTI)

The Cryogenic Dark Matter Search (CDMS) experiment is designed to search for dark matter in the form of the Weakly Interacting Massive Particles (WIMPs). For this purpose, CDMS uses detectors based on crystals of Ge and Si, operated at the temperature of 20 mK, and providing a two-fold signature of an interaction: the ionization and the athermal phonon signals. The two signals, along with the passive and active shielding of the experimental setup, and with the underground experimental sites, allow very effective suppression and rejection of different types of backgrounds. This dissertation presents the commissioning and the results of the first WIMP-search run performed by the CDMS collaboration at the deep underground site at the Soudan mine in Minnesota. We develop different methods of suppressing the dominant background due to the electron-recoil events taking place at the detector surface and we apply these algorithms to the data set. These results place the world's most sensitive limits on the WIMP-nucleon spin-independent elastic-scattering cross-section. Finally, they examine the compatibility of the supersymmetric WIMP-models with the direct-detection experiments (such as CDMS) and discuss the implications of the new CDMS result on these models.

Mandic, Vuk; /UC, Berkeley

2004-06-01T23:59:59.000Z

31

New Electron Beam-Dump Experiments to Search for MeV to few-GeV Dark Matter  

E-Print Network (OSTI)

In a broad class of consistent models, MeV to few-GeV dark matter interacts with ordinary matter through weakly coupled GeV-scale mediators. We show that a suitable meter-scale (or smaller) detector situated downstream of an electron beam-dump can sensitively probe dark matter interacting via sub-GeV mediators, while B-factory searches cover the 1-5 GeV range. Combined, such experiments explore a well-motivated and otherwise inaccessible region of dark matter parameter space with sensitivity several orders of magnitude beyond existing direct detection constraints. These experiments would also probe invisibly decaying new gauge bosons ("dark photons") down to kinetic mixing of \\epsilon ~ 10^{-4}, including the range of parameters relevant for explaining the (g-2)_{\\mu} discrepancy. Sensitivity to other long-lived dark sector states and to new milli-charge particles would also be improved.

Eder Izaguirre; Gordan Krnjaic; Philip Schuster; Natalia Toro

2013-07-24T23:59:59.000Z

32

The Cryogenic Dark Matter Search (CDMS-II) Experiment: First Results from the Soudan Mine  

Science Conference Proceedings (OSTI)

There is an abundance of evidence that the majority of the mass of the universe is in the form of non-baryonic non-luminous matter that was non-relativistic at the time when matter began to dominate the energy density. Weakly Interacting Massive Particles, or WIMPs, are attractive cold dark matter candidates because they would have a relic abundance today of {approx}0.1 which is consistent with precision cosmological measurements. WIMPs are also well motivated theoretically. Many minimal supersymmetric extensions of the Standard Model have WIMPs in the form of the lightest supersymmetric partner, typically taken to be the neutralino. The CDMS II experiment searches for WIMPs via their elastic scattering off of nuclei. The experiment uses Ge and Si ZIP detectors, operated at ZIP phonon response which improves the rejection of events scattering near the detector surface. The CDMS collaboration has recently commissioned its experimental installation at the Soudan Mine. This thesis presents an analysis of the data from the first WIMP search at the Soudan Mine. The results of this analysis set the world's lowest exclusion limit making the CDMS II experiment at Soudan the most sensitive WIMP search to this date.

Chang, Clarence Leeder; /Stanford U., Phys. Dept.

2004-09-01T23:59:59.000Z

33

First Results from the Cryogenic Dark Matter Search in the Soudan Underground Lab  

E-Print Network (OSTI)

We report the first results from a search for weakly interacting massive particles (WIMPs) in the Cryogenic Dark Matter Search (CDMS) experiment at the Soudan Underground Laboratory. Four Ge and two Si detectors were operated for 52.6 live days, providing 19.4 kg-d of Ge net exposure after cuts for recoil energies between 10-100 keV. A blind analysis was performed using only calibration data to define the energy threshold and selection criteria for nuclear-recoil candidates. These data set the world's lowest exclusion limits on the coherent WIMP-nucleon scalar cross-section for all WIMP masses above 15 GeV, ruling out a significant range of neutralino supersymmetric models. The minimum of the limit curve at the 90% C.L. is 4 x 10^{-43} cm^2 at a WIMP mass of 60 GeV.

Akerib, D S; Armel-Funkhouser, M S; Attisha, M J; Baudis, L; Bauer, D A; Beaty, J; Brink, P L; Bunker, R; Cabrera, B; Caldwell, D O; Callahan, D; Castle, J P; Chang, C L; Choate, R; Crisler, M B; Cushman, P; Dixon, R; Dragowsky, M R; Driscoll, D D; Duong, L; Emes, J; Ferril, R; Filippini, J; Gaitskell, R J; Haldeman, M; Hale, D; Holmgren, D; Huber, M E; Johnson, B; Johnson, W; Kamat, S; Kozlovsky, M; Kula, L; Kyre, S; Lambin, B; Lu, A; Mahapatra, R; Manalaysay, A G; Mandic, V; May, J; McDonald, R; Merkel, B; Meunier, P; Mirabolfathi, N; Morrison, S; Nelson, H; Nelson, R; Novak, L; Ogburn, R W; Orr, S; Perera, T A; Perillo-Isaac, M C; Ramberg, E; Rau, W; Reisetter, A; Ross, R R; Saab, T; Sadoulet, B; Sander, J; Savage, C; Schmitt, R L; Schnee, R W; Seitz, D N; Serfass, B; Smith, A; Smith, G; Spadafora, A L; Sundqvist, K; Thompson, J P F; Tomada, A; Wang, G; Williams, J; Yellin, S; Young, B A

2004-01-01T23:59:59.000Z

34

Dark Matter  

NLE Websites -- All DOE Office Websites (Extended Search)

with other matter. Based on observations of the relationships between mass and gravity and the speed of the stars and other cosmological systems, scientists believe that...

35

Infrared Searches for Dark Matter in the Form of Brown Dwarfs  

E-Print Network (OSTI)

Brown dwarfs, stars with insufficient mass to burn hydrogen, could contribute to the dark matter in the Galactic disk, galactic halos or even a background critical density. We consider the detectability of such brown dwarfs in various scenarios, extending previous work by allowing for the possibility that they may have an extended mass spectrum or be clumped into dark clusters. We investigate the constraints placed on such scenarios by the \\iras survey. Whilst an extrapolation of the mass function of visible disk stars makes it unlikely that brown dwarfs comprise all of the proposed disk dark matter, \\iras does not exclude brown dwarfs providing the dark matter in our own halo or a cosmological background. Neither does it improve on existing dynamical constraints on the mass and radius of brown dwarf clusters in our halo. Future satellites such as \\iso and \\sirtf will either detect brown dwarfs or brown dwarf clusters or else severely constrain their contribution to the dark matter.

E. J. Kerins; B. J. Carr

1993-09-02T23:59:59.000Z

36

Exothermic dark matter  

E-Print Network (OSTI)

We propose a novel mechanism for dark matter to explain the observed annual modulation signal at DAMA/LIBRA which avoids existing constraints from every other dark matter direct detection experiment including CRESST, CDMS, ...

Graham, Peter W.

37

Development of a Navigator and Imaging Techniques for the Cryogenic Dark Matter Search Detectors  

Science Conference Proceedings (OSTI)

This project contributes to the detection of flaws in the germanium detectors for the Cryogenic Dark Matter Search (CDMS) experiment. Specifically, after imaging the detector surface with a precise imaging and measuring device, they developed software to stitch the resulting images together, applying any necessary rotations, offsets, and averaging, to produce a smooth image of the whole detector that can be used to detect flaws on the surface of the detector. These images were also tiled appropriately for the Google Maps API to use as a navigation tool, allowing viewers to smoothly zoom and pan across the detector surface. Automated defect identification can now be implemented, increasing the scalability of the germanium detector fabrication.

Wilen, Chris; /Carleton Coll. /KIPAC, Menlo Park

2011-06-22T23:59:59.000Z

38

The quark contents of the nucleon and their implication for dark matter search  

E-Print Network (OSTI)

We present results concerning the light and strange quark contents of the nucleon using $N_f=2+1+1$ flavours of maximally twisted mass fermions. The corresponding $\\sigma$-terms are casting light on the origin of the nucleon mass and their values are important to interpret experimental data from direct dark matter searches. We discuss our strategy to estimate systematic uncertainties arising in our computations. Our preliminary results for the $\\sigma-$terms read $\\sigma_{\\pi N} = 37(2.6)(24.7) \\mev$ and $\\sigma_s=28(8)(10) \\mev$. We present our recent final analysis of the $y_N$ parameter and found $y_N=0.135(46)$ including systematics\\cite{Alexandrou:2013nda}.

C. Alexandrou; M. Constantinou; V. Drach; K. Hadjiyiannakou; K. Jansen; G. Koutsou; A. Strelchenko; A. Vaquero

2013-11-24T23:59:59.000Z

39

The Cryogenic Dark Matter Search (CDMS-II) Experiment: First Results from the Soudan Mine  

SciTech Connect

There is an abundance of evidence that the majority of the mass of the universe is in the form of non-baryonic non-luminous matter that was non-relativistic at the time when matter began to dominate the energy density. Weakly Interacting Massive Particles, or WIMPs, are attractive cold dark matter candidates because they would have a relic abundance today of {approx}0.1 which is consistent with precision cosmological measurements. WIMPs are also well motivated theoretically. Many minimal supersymmetric extensions of the Standard Model have WIMPs in the form of the lightest supersymmetric partner, typically taken to be the neutralino. The CDMS II experiment searches for WIMPs via their elastic scattering off of nuclei. The experiment uses Ge and Si ZIP detectors, operated at <50 mK, which simultaneously measure the ionization and athermal phonons produced by the scattering of an external particle. The dominant background for the experiment comes from electromagnetic interactions taking place very close to the detector surface. Analysis of the phonon signal from these interactions makes it possible to discriminate them from interactions caused by WIMPs. This thesis presents the details of an important aspect of the phonon pulse shape analysis known as the ''Lookup Table Correction''. The Lookup Table Correction is a position dependent calibration of the ZIP phonon response which improves the rejection of events scattering near the detector surface. The CDMS collaboration has recently commissioned its experimental installation at the Soudan Mine. This thesis presents an analysis of the data from the first WIMP search at the Soudan Mine. The results of this analysis set the world's lowest exclusion limit making the CDMS II experiment at Soudan the most sensitive WIMP search to this date.

Chang, Clarence Leeder; /Stanford U., Phys. Dept.

2004-09-01T23:59:59.000Z

40

Advancing the search for dark matter : from CDMS II to SuperCDMS  

E-Print Network (OSTI)

An overwhelming proportion of the universe (83% by mass) is composed of particles we know next to nothing about. Detecting these dark matter particles directly, through hypothesized weak-force-mediated recoils with nuclear ...

Hertel, Scott A. (Scott Alexander)

2012-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "dark matter searches" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


41

Implications of Direct Dark Matter Constraints for Minimal Supersymmetric Standard Model Higgs Boson Searches at the Tevatron  

E-Print Network (OSTI)

Searches for the Minimal Supersymmetric Standard Model (MSSM) Higgs bosons are among the most promising channels for exploring new physics at the Tevatron. In particular, interesting regions of large $\\tan \\beta$ and small $m_A$ are probed by searches for heavy neutral Higgs bosons, A and H, when they decay to $\\tau^+ \\tau^-$ and $b\\bar{b}$. At the same time, direct searches for dark matter, such as CDMS, attempt to observe neutralino dark matter particles scattering elastically off nuclei. This can occur through t-channel Higgs exchange, which has a large cross section in the case of large $\\tan \\beta$ and small $m_A$. As a result, there is a natural interplay between the heavy, neutral Higgs searches at the Tevatron and the region of parameter space explored by CDMS. We show that if the lightest neutralino makes up the dark matter of our universe, current limits from CDMS strongly constrain the prospects of heavy, neutral MSSM Higgs discovery at the Tevatron (at 3 sigma with 4 fb^-1 per experiment) unless $|\\mu| \\gsim$ 400 GeV. The limits of CDMS projected for 2007 will increase this constraint to $|\\mu| \\gsim$ 800 GeV. On the other hand, if CDMS does observe neutralino dark matter in the near future, it will make the discovery of heavy, neutral MSSM Higgs bosons far more likely at the Tevatron.

Marcela Carena; Dan Hooper; Peter Skands

2006-03-23T23:59:59.000Z

42

WIMP Dark Matter Limit-Direct Detection Data and Sensitivity Plots from the Cryogenic Dark Matter Search II and the University of California at Santa Barbara  

DOE Data Explorer (OSTI)

Expectations for non-baryonic dark matter are founded principally in Big Bang nucleosynthesis calculations, which indicate that the missing mass of the universe is not likely to be baryonic. The supersymmetric standard model (SUSY) offers a promising framework for expectations of particle species which could satisfy the observed properties of dark matter. WIMPs are the most likely SUSY candidate for a dark matter particle. The High Energy Physics Group at University of California, Santa Barbara, is part of the CDMSII Collaboration and have provided the Interactive Plotter for WIMP Dark Matter Limit-Direct Detection Data on their website. They invite other collaborations working on dark matter research to submit datasets and, as a result, have more than 150 data sets now available for use with the plotting tool. The published source of the data is provided with each data set.

43

Search for Higgs Bosons in SUSY cascade decays and neutralino dark matter.  

SciTech Connect

The minimal supersymmetric extension of the standard model (MSSM) is a well-motivated theoretical framework, which contains an extended Higgs sector, including a light Higgs with standard model-like properties in most of the parameter space. Because of the large QCD background, searches for such a Higgs, decaying into a pair of bottom quarks, are very challenging at the LHC. It has been long realized that the situation may be ameliorated by searching for Higgs bosons in supersymmetric decay chains. Moreover, it has been recently suggested that the b{bar b} decay channel may be observed in standard production channels by selecting boosted Higgs bosons, which may be easily identified from the QCD background. Such boosted Higgs bosons are frequent in the MSSM, since they are produced from decays of heavy colored supersymmetric particles. Previous works have emphasized the possibility of observing boosted Higgs bosons in the light Higgsino region. In this work, we study the same question in the regions of parameter space consistent with a neutralino dark matter relic density, analyzing its dependence on the nonstandard Higgs boson, slepton, and squark masses, as well as on the condition of gaugino mass unification. In general, we conclude that, provided sleptons are heavier than the second lightest neutralinos, the presence of boosted Higgs is a common MSSM feature, implying excellent prospects for observation of the light MSSM Higgs boson in the near future.

Gori, S.; Schwaller, P.; Wagner, C. E. M. (High Energy Physics); (Univ. of Chicago); (Northwestern Univ.); (Univ. of Illinois at Chicago)

2011-06-24T23:59:59.000Z

44

The Cryogenic System for the Panda-X Dark Matter Search Experiment  

E-Print Network (OSTI)

Panda-X is a liquid xenon dual-phase detector for the Dark Matter Search. The first modestly-sized module will soon be installed in the China JinPing Deep Underground Laboratory in Sichuan province, P.R. China. The cryogenics system is designed to handle much larger detectors, even the final version in the ton scale. Special attention has been paid to the reliability, serviceability, and adaptability to the requirements of a growing experiment. The system is cooled by a single Iwatani PC150 Pulse Tube Refrigerator. After subtracting all thermal losses, the remaining cooling power is still 82W. The fill speed was 9 SLPM, but could be boosted by LN2 assisted cooling to 40 SLPM. For the continuous recirculation and purification through a hot getter, a heat exchanger was employed to reduce the required cooling power. The recirculation speed is limited to 35 SLPM by the gas pump. At this speed, recirculation only adds 18.5 W to the heat load of the system, corresponding to a 95.2 % efficiency of the heat exchanger.

Zhao Li; Karl Ludwig Giboni; Haowei Gong; Xiangdong Ji; Andy Tan

2012-07-21T23:59:59.000Z

45

Debris Flows in Direct Dark Matter Searches-The modulation effect  

E-Print Network (OSTI)

The effect of some possible non standard WIMP velocity distributions, like the Debris Flows recently proposed, on the direct dark matter detection rates is investigated. We find that such distributions may be deciphered from the data, especially if the time variation of the event rates due to the annual motion of the Earth is observed

J. D. Vergados

2012-02-14T23:59:59.000Z

46

Dark Energy and Dark Matter Models  

E-Print Network (OSTI)

We revisit the problems of dark energy and dark matter and several models designed to explain them, in the light of some latest findings.

Sidharth, Burra G

2013-01-01T23:59:59.000Z

47

Dark Energy and Dark Matter Models  

E-Print Network (OSTI)

We revisit the problems of dark energy and dark matter and several models designed to explain them, in the light of some latest findings.

Burra G. Sidharth

2013-03-14T23:59:59.000Z

48

Dark matter at colliders  

SciTech Connect

We show that colliders can impose strong constraints on dark matter. We take an effective field theory approach where dark matter couples to quarks and gluons through high dimensional operators. We discuss limits on interactions of dark matter and hadronic matter from the ATLAS experiment at the Large Hadron Collider (LHC). For spin-independent scattering, the LHC limits are stronger than those from direct detection experiments for light WIMPs. For spin-dependent scattering, the LHC sets better limits over much of parameter space.

Yu Haibo [Department of Physics, University of Michigan, Ann Arbor, MI, 48109 (United States)

2013-05-23T23:59:59.000Z

49

Dark Matter and Dark Energy  

E-Print Network (OSTI)

This is a short review, aimed at a general audience, of several current subjects of research in cosmology. The topics discussed include the cosmic microwave background (CMB), with particular emphasis on its relevance for testing inflation; dark matter, with a brief review of astrophysical evidence and more emphasis on particle candidates; and cosmic acceleration and some of the ideas that have been put forward to explain it. A glossary of technical terms and acronyms is provided.

Marc Kamionkowski

2007-06-20T23:59:59.000Z

50

Dark Matter and Dark Energy  

E-Print Network (OSTI)

This is a short review, aimed at a general audience, of several current subjects of research in cosmology. The topics discussed include the cosmic microwave background (CMB), with particular emphasis on its relevance for testing inflation; dark matter, with a brief review of astrophysical evidence and more emphasis on particle candidates; and cosmic acceleration and some of the ideas that have been put forward to explain it. A glossary of technical terms and acronyms is provided.

Kamionkowski, Marc

2007-01-01T23:59:59.000Z

51

Dark matter dynamics  

E-Print Network (OSTI)

N-body simulations have revealed a wealth of information about dark matter halos but their results are largely empirical. Here we attempt to shed light on simulation results by using a combination of analytic and numerical ...

Zukin, Phillip Gregory

2012-01-01T23:59:59.000Z

52

Dark matter: Theoretical perspectives  

SciTech Connect

I both review and make the case for the current theoretical prejudice: a flat Universe whose dominant constituent is nonbaryonic dark matter, emphasizing that this is still a prejudice and not yet fact. The theoretical motivation for nonbaryonic dark matter is discussed in the context of current elementary-particle theory, stressing that: (1) there are no dark matter candidates within the standard model of particle physics; (2) there are several compelling candidates within attractive extensions of the standard model of particle physics; and (3) the motivation for these compelling candidates comes first and foremost from particle physics. The dark-matter problem is now a pressing issue in both cosmology and particle physics, and the detection of particle dark matter would provide evidence for ``new physics.`` The compelling candidates are: a very light axion ( 10{sup {minus}6} eV--10{sup {minus}4} eV); a light neutrino (20 eV--90 eV); and a heavy neutralino (10 GeV--2 TeV). The production of these particles in the early Universe and the prospects for their detection are also discussed. I briefly mention more exotic possibilities for the dark matter, including a nonzero cosmological constant, superheavy magnetic monopoles, and decaying neutrinos.

Turner, M.S. [Chicago Univ., IL (United States). Enrico Fermi Inst.]|[Fermi National Accelerator Lab., Batavia, IL (United States)

1993-01-01T23:59:59.000Z

53

Dark Matter Jets at the LHC  

SciTech Connect

We argue that dark matter particles which have strong interactions with the Standard Model particles are not excluded by current astrophysical constraints. These dark matter particles have unique signatures at colliders; instead of missing energy, the dark matter particles produce jets. We propose a new search strategy for such strongly interacting particles by looking for a signal of two trackless jets. We show that suitable cuts can plausibly allow us to find these signals at the LHC even in early data.

Bai, Yang; /SLAC; Rajaraman, Arvind; /UC, Irvine

2012-03-28T23:59:59.000Z

54

Background Rejection in the DMTPC Dark Matter Search Using Charge Signals  

E-Print Network (OSTI)

The Dark Matter Time Projection Chamber (DMTPC) collaboration is developing a low pressure gas TPC for detecting Weakly Interacting Massive Particle (WIMP)-nucleon interactions. Optical readout with CCD cameras allows for the detection of the daily modulation of the direction of the dark matter wind. In order to reach sensitivities required for WIMP detection, the detector needs to minimize backgrounds from electron recoils. This paper demonstrates that a simplified CCD analysis achieves $7.3\\times10^{-5}$ rejection of electron recoils while a charge analysis yields an electron rejection factor of $3.3\\times10^{-4}$ for events with $^{241}$Am-equivalent ionization energy loss between 40 keV and 200 keV. A combined charge and CCD analysis yields a background-limited upper limit of $1.1\\times10^{-5}$ (90% confidence level) for the rejection of $\\gamma$ and electron events. Backgrounds from alpha decays from the field cage are eliminated by introducing a veto electrode that surrounds the sensitive region in the TPC. CCD-specific backgrounds are reduced more than two orders of magnitude when requiring a coincidence with the charge readout.

J. P. Lopez; D. Dujmic; S. Ahlen; J. B. R. Battat; C. Deaconu; P. Fisher; S. Henderson; A. Inglis; A. Kaboth; J. Monroe; G. Sciolla; H. Tomita; H. Wellenstein; R. Yamamoto

2013-01-24T23:59:59.000Z

55

Baryon destruction by asymmetric dark matter  

SciTech Connect

We investigate new and unusual signals that arise in theories where dark matter is asymmetric and carries a net antibaryon number, as may occur when the dark matter abundance is linked to the baryon abundance. Antibaryonic dark matter can cause induced nucleon decay by annihilating visible baryons through inelastic scattering. These processes lead to an effective nucleon lifetime of 10{sup 29}-10{sup 32} yrs in terrestrial nucleon decay experiments, if baryon number transfer between visible and dark sectors arises through new physics at the weak scale. The possibility of induced nucleon decay motivates a novel approach for direct detection of cosmic dark matter in nucleon decay experiments. Monojet searches (and related signatures) at hadron colliders also provide a complementary probe of weak-scale dark-matter-induced baryon number violation. Finally, we discuss the effects of baryon-destroying dark matter on stellar systems and show that it can be consistent with existing observations.

Davoudiasl, Hooman [Department of Physics, Brookhaven National Laboratory, Upton, New York 11973 (United States); Morrissey, David E.; Tulin, Sean [Theory Group, TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia V6T 2A3 (Canada); Sigurdson, Kris [Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1 (Canada)

2011-11-01T23:59:59.000Z

56

First measurement of the Head-Tail directional nuclear recoil signature at energies relevant to WIMP dark matter searches  

E-Print Network (OSTI)

We present first evidence for the so-called Head-Tail asymmetry signature of neutron-induced nuclear recoil tracks at energies down to 1.5 keV/amu using the 1m^3 DRIFT-IIc dark matter detector. This regime is appropriate for recoils induced by Weakly Interacting Massive Particle (WIMPs) but one where the differential ionization is poorly understood. We show that the distribution of recoil energies and directions induced here by Cf-252 neutrons matches well that expected from massive WIMPs. The results open a powerful new means of searching for a galactic signature from WIMPs.

S. Burgos; E. Daw; J. Forbes; C. Ghag; M. Gold; C. Hagemann; V. A. Kudryavtsev; T. B. Lawson; D. Loomba; P. Majewski; D. Muna; A. StJ. Murphy; G. G. Nicklin; S. M. Paling; A. Petkov; S. J. S. Plank; M. Robinson; N. Sanghi; D. P. Snowden-Ifft; N. J. C. Spooner; J. Turk; E. Tziaferi

2008-09-10T23:59:59.000Z

57

Little Higgs Dark Matter  

E-Print Network (OSTI)

The introduction of T parity dramatically improves the consistency of Little Higgs models with precision electroweak data, and renders the lightest T-odd particle (LTP) stable. In the Littlest Higgs model with T parity, the LTP is typically the T-odd heavy photon, which is weakly interacting and can play the role of dark matter. We analyze the relic abundance of the heavy photon, including its coannihilations with other T-odd particles, and map out the regions of the parameter space where it can account for the observed dark matter. We evaluate the prospects for direct and indirect discovery of the heavy photon dark matter. The direct detection rates are quite low and a substantial improvement in experimental sensitivity would be required for observation. A substantial flux of energetic gamma rays is produced in the annihilation of the heavy photons in the galactic halo. This flux can be observed by the GLAST telescope, and, if the distribution of dark matter in the halo is favorable, by ground-based telescope arrays such as VERITAS and HESS.

Andreas Birkedal; Andrew Noble; Maxim Perelstein; Andrew Spray

2006-03-09T23:59:59.000Z

58

The C-4 Dark Matter Experiment  

Science Conference Proceedings (OSTI)

Abstract We describe the experimental design of C-4, an expansion of the CoGeNT dark matter search to four identical detectors each approximately three times the mass of the p-type point contact (PPC) germanium diode presently taking data at the Soudan Underground Laboratory. Expected reductions of radioactive backgrounds and energy threshold are discussed, including an estimate of the additional sensitivity to low-mass dark matter candidates to be obtained with this search.

Bonicalzi, Ricco; Collar, J. I.; Colaresi, J.; Fast, James E.; Fields, N.; Fuller, Erin S.; Hai, M.; Hossbach, Todd W.; Kos, Marek S.; Orrell, John L.; Overman, Cory T.; Reid, Douglas J.; VanDevender, Brent A.; Wiseman, Clinton G.; Yocum, K. M.

2013-06-01T23:59:59.000Z

59

A quantized frequency reference in the short-ranged gravity potential and its application for dark matter and dark energy searches  

E-Print Network (OSTI)

The evidence for the observation of the Higgs spin-0-boson as a manifestation of a scalar field provides the missing corner stone for the standard model of particles (SM). However, the SM fails to explain the non-visible but gravitationally active part of the universe. Its nature is unknown but the confirmation of a scalar Higgs is giving a boost to scalar-field-theories. So far gravity experiments and observations performed at different distances find no deviation from Newton's gravity law. Therefore dark energy must possess a screening mechanism which suppresses the scalar-mediated fifth force. Our line of attack is a novel gravity experiment with neutrons based on a quantum interference technique. The spectroscopic measurement of quantum states on resonances with an external coupling makes this a powerful search for dark matter and dark energy contributions in the universe. Quantum states in the gravity potential are intimately related to other scalar field or spin-0-bosons if they exist. If the reason is that some undiscovered particle interact with a neutron, this results in a measurable energy shift of quantum states in the gravity potential, because for neutrons the screening effect is absent. We use Gravity Resonance Spectroscopy to measure the energy splitting at the highest level of precision, providing a constraint on any possible new interaction. We obtain a sensitivity of 10^-14 eV. We set an experimental limit on any fifth force, in particular on parameter \\betagravity is understood at this improved level of precision.

T. Jenke; G. Cronenberg; P. Geltenbort; A. N. Ivanov; T. Lauer; T. Lins; U. Schmidt; H. Saul; H. Abele

2012-08-19T23:59:59.000Z

60

Anisotropic diffusion of electrons in liquid xenon with application to improving the sensitivity of direct dark matter searches  

SciTech Connect

Electron diffusion in a liquid xenon time projection chamber has recently been used to infer the z coordinate of a particle interaction, from the width of the electron signal. The goal of this technique is to reduce the background event rate by discriminating edge events from bulk events. Analyses of dark matter search data which employ it would benefit from increased longitudinal electron diffusion. We show that a significant increase is expected if the applied electric field is decreased. This observation is trivial to implement but runs contrary to conventional wisdom and practice. We also extract a first measurement of the longitudinal diffusion coefficient, and confirm the expectation that electron diffusion in liquid xenon is highly anisotropic under typical operating conditions.

Sorensen, P

2011-02-14T23:59:59.000Z

Note: This page contains sample records for the topic "dark matter searches" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


61

Dark Matter Detectors as Dark Photon Helioscopes  

E-Print Network (OSTI)

Light new particles with masses below 10 keV, often considered as a plausible extension of the Standard Model, will be emitted from the solar interior, and can be detected on the Earth with a variety of experimental tools. Here we analyze the new "dark" vector state V, a massive vector boson mixed with the photon via an angle kappa, that in the limit of the small mass m_V has its emission spectrum strongly peaked at low energies. Thus, we utilize the constraints on the atomic ionization rate imposed by the results of the XENON10 experiment to set the limit on the parameters of this model: kappa times m_V< 3 times10^{-12} eV. This makes low-threshold Dark Matter experiments the most sensitive dark vector helioscopes, as our result not only improves current experimental bounds from other searches by several orders of magnitude, but also surpasses even the most stringent astrophysical and cosmological limits in a seven-decade-wide interval of m_V. We generalize this approach to other light exotic particles, and set the most stringent direct constraints on "mini-charged" particles.

Haipeng An; Maxim Pospelov; Josef Pradler

2013-04-11T23:59:59.000Z

62

Dark Matter Studies Entrain Nuclear Physics  

E-Print Network (OSTI)

We review theoretically well-motivated dark-matter candidates, and pathways to their discovery, in the light of recent results from collider physics, astrophysics, and cosmology. Taken in aggregate, these encourage broader thinking in regards to possible dark-matter candidates --- dark-matter need not be made of "WIMPs," i.e., elementary particles with weak-scale masses and interactions. Facilities dedicated to nuclear physics are well-poised to investigate certain non-WIMP models. In parallel to this, developments in observational cosmology permit probes of the relativistic energy density at early epochs and thus provide new ways to constrain dark-matter models, provided nuclear physics inputs are sufficiently well-known. The emerging confluence of accelerator, astrophysical, and cosmological constraints permit searches for dark-matter candidates in a greater range of masses and interaction strengths than heretofore possible.

Susan Gardner; George Fuller

2013-03-19T23:59:59.000Z

63

Unravelling the Dark Matter - Dark Energy Paradigm  

E-Print Network (OSTI)

The standard LambdaCDM model of cosmology is usually understood to arise from demanding that the Friedmann-Lemaitre-Robertson-Walker (FLRW) metric satisfy the General Relativity dynamics for spacetime metrics. The FLRW data-based dominant parameter values, Omega_Lambda=0.73 and Omega_m=0.27 for the dark energy and dark matter+matter, respectively, are then determined by fitting the supernova red-shift data. However in the pressure-less flat-space case the LambdaCDM model is most easily derived from Newtonian gravity, and which was based on the special case of planetary motion in the solar system. Not surprisingly when extended to galactic rotations and cosmology Newtonian dynamics is found to be wanting, and the fix-up involves introducing dark matter and dark energy, as shown herein. However a different theory of gravity leads to a different account of galactic rotations and cosmology, and does not require dark matter nor dark energy to fit the supernova data. It is shown that fitting the LambdaCDM model to this new model, and so independently of the actual supernova data, requires the LambdaCDM model parameters to be those given above. Hence we conclude that dark energy and dark matter are no more than mathematical artifacts to fix-up limitations of Newtonian gravity. Various other data are also briefly reviewed to illustrate other successful tests of this new theory of gravity.

Reginald T Cahill

2009-01-26T23:59:59.000Z

64

A dark matter scaling relation from mirror dark matter  

E-Print Network (OSTI)

Mirror dark matter, and other similar dissipative dark matter candidates, need an energy source to stabilize dark matter halos in spiral galaxies. It has been suggested previously that ordinary supernovae can potentially supply the required energy. By matching the energy supplied to the halo from supernovae to that lost due to radiative cooling, we here derive a rough scaling relation, $R_{SN} \\propto \\rho_0 r_0^2$ ($R_{SN}$ is the supernova rate and $\\rho_0, \\ r_0$ the dark matter central density and core radius). Such a relation is consistent with dark matter properties inferred from studies of spiral galaxies with halo masses larger than $3\\times 10^{11} M_\\odot$. We speculate that other observed galaxy regularities might be explained within the framework of such dissipative dark matter.

R. Foot

2013-03-07T23:59:59.000Z

65

Dark Matter and Dark Energy: A Physicist's Perspective  

E-Print Network (OSTI)

For physicists, recent developments in astrophysics and cosmology present exciting challenges. We are conducting "experiments" in energy regimes some of which will be probed by accelerators in the near future, and others which are inevitably the subject of more speculative theoretical investigations. Dark matter is an area where we have hope of making discoveries both with accelerator experiments and dedicated searches. Inflation and dark energy lie in regimes where presently our only hope for a fundamental understanding lies in string theory.

Michael Dine

2001-07-30T23:59:59.000Z

66

A DEEP SEARCH FOR EXTENDED RADIO CONTINUUM EMISSION FROM DWARF SPHEROIDAL GALAXIES: IMPLICATIONS FOR PARTICLE DARK MATTER  

Science Conference Proceedings (OSTI)

We present deep radio observations of four nearby dwarf spheroidal (dSph) galaxies, designed to detect extended synchrotron emission resulting from weakly interacting massive particle (WIMP) dark matter annihilations in their halos. Models by Colafrancesco et al. (CPU07) predict the existence of angularly large, smoothly distributed radio halos in such systems, which stem from electron and positron annihilation products spiraling in a turbulent magnetic field. We map a total of 40.5 deg{sup 2} around the Draco, Ursa Major II, Coma Berenices, and Willman 1 dSphs with the Green Bank Telescope (GBT) at 1.4 GHz to detect this annihilation signature, greatly reducing discrete-source confusion using the NVSS catalog. We achieve a sensitivity of {sigma}{sub sub} {approx}energies from the two-year Fermi Large Area Telescope data. We discuss three avenues for improving the constraints on ({sigma}v){sub {chi}} presented here, and conclude that deep radio observations of dSphs are highly complementary to indirect WIMP searches at higher energies.

Spekkens, Kristine [Department of Physics, Royal Military College of Canada, P.O. Box 17000, Station Forces, Kingston, Ontario K7K 7B4 (Canada); Mason, Brian S. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475 (United States); Aguirre, James E. [Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 (United States); Nhan, Bang, E-mail: kristine.spekkens@rmc.ca [Department of Astrophysical and Planetary Sciences, University of Colorado, 391 UCB, Boulder, CO 80309 (United States)

2013-08-10T23:59:59.000Z

67

Cold Dark Matter Resuscitated?  

E-Print Network (OSTI)

The Cold Dark Matter (CDM) model has an elegant simplicitly which makes it very predictive, but when its parameters are fixed at their `canonical' values its predictions are in conflict with observational data. There is, however, much leeway in the initial conditions within the CDM framework. We advocate a re-examination of the CDM model, taking into account modest variation of parameters from their canonical values. We find that CDM models with $n=0.8$--0.9 and $h=0.45$--0.50 can fit the available data. Our ``best fit'' CDM model has $n=0.9$, $h=0.45$ and $C_2^{T}/C_2^{S}=0.7$. We discuss the current state of observations which could definitely rule out this model.

Martin White; Douglas Scott; Joe Silk; Marc Davis

1995-08-02T23:59:59.000Z

68

Unified Description of Dark Energy and Dark Matter  

E-Print Network (OSTI)

Dark energy in the universe is assumed to be vacuum energy. The energy-momentum of vacuum is described by a scale-dependent cosmological constant. The equations of motion imply for the density of matter (dust) the sum of the usual matter density (luminous matter) and an additional matter density (dark matter) similar to the dark energy. The scale-dependent cosmological constant is given up to an exponent which is approximated by the experimentally decided density parameters of dark matter and dark energy. This yields that dark matter is one third of dark energy for all times implying an explanation of the coincidence of dark matter and dark energy. In the final state, the universe becomes dark, consisting of dark matter and dark energy.

Walter Petry

2008-10-23T23:59:59.000Z

69

Experiment Profile: DAMIC NAME: Dark Matter In CCDs, or DAMIC  

NLE Websites -- All DOE Office Websites (Extended Search)

DAMIC DAMIC NAME: Dark Matter In CCDs, or DAMIC ThE ORIGIN OF ThE NAME: DAMIC searches for dark matter using Charge Coupled Devices. These digital chips register light that gets converted into a digital value a computer can store. WHAT WILL THIS TELL? Everything you see, visible matter, makes up 4 percent of the universe. Dark matter and dark energy make up the rest of the universe. Physicists understand that dark matter acts as an invisible source of gravity, but little more. DAMIC seeks to pinpoint what particles make up dark matter, which will help explain how the universe came to exist. Without the added gravitational attraction of dark matter, stars and galaxies would have never formed. The expansion of the universe after the Big Bang would have dispersed visible

70

On the Nature of Dark Matter and Dark Energy  

E-Print Network (OSTI)

It is shown that some problems connected with dark matter and dark energy can be solved in the framework of the byuon theory

Yu. A. Baurov; I. F. Malov

2007-10-16T23:59:59.000Z

71

Dark Matter in the Coming Decade: Complementary Paths to Discovery and Beyond  

E-Print Network (OSTI)

In this Report we discuss the four complementary searches for the identity of dark matter: direct detection experiments that look for dark matter interacting in the lab, indirect detection experiments that connect lab signals to dark matter in our own and other galaxies, collider experiments that elucidate the particle properties of dark matter, and astrophysical probes sensitive to non-gravitational interactions of dark matter. The complementarity among the different dark matter searches is discussed qualitatively and illustrated quantitatively in several theoretical scenarios. Our primary conclusion is that the diversity of possible dark matter candidates requires a balanced program based on all four of those approaches.

Sebastian Arrenberg; Howard Baer; Vernon Barger; Laura Baudis; Daniel Bauer; James Buckley; Matthew Cahill-Rowley; Randel Cotta; Alex Drlica-Wagner; Jonathan L. Feng; Stefan Funk; JoAnne Hewett; Dan Hooper; Ahmed Ismail; Manoj Kaplinghat; Kyoungchul Kong; Alexander Kusenko; Konstantin Matchev; Mathew McCaskey; Daniel McKinsey; Dan Mickelson; Tom Rizzo; David Sanford; Gabe Shaughnessy; William Shepherd; Tim M. P. Tait; Xerxes Tata; Sean Tulin; Alexander M. Wijangco; Matthew Wood; Jonghee Yoo; Hai-Bo Yu

2013-10-31T23:59:59.000Z

72

Direct Detection of Dark Matter Debris Flows  

E-Print Network (OSTI)

Tidal stripping of dark matter from subhalos falling into the Milky Way produces narrow, cold tidal streams as well as more spatially extended "debris flows" in the form of shells, sheets, and plumes. Here we focus on the debris flow in the Via Lactea II simulation, and show that this incompletely phase-mixed material exhibits distinctive high velocity behavior. Unlike tidal streams, which may not necessarily intersect the Earth's location, debris flow is spatially uniform at 8 kpc and thus guaranteed to be present in the dark matter flux incident on direct detection experiments. At Earth-frame speeds greater than 450 km/s, debris flow comprises more than half of the dark matter at the Sun's location, and up to 80% at even higher speeds. Therefore, debris flow is most important for experiments that are particularly sensitive to the high speed tail of the dark matter distribution, such as searches for light or inelastic dark matter or experiments with directional sensitivity. We show that debris flow yields a distinctive recoil energy spectrum and a broadening of the distribution of incidence direction.

Michael Kuhlen; Mariangela Lisanti; David N. Spergel

2012-01-31T23:59:59.000Z

73

A search for particle dark matter using cryogenic germanium and silicon detectors in the one- and two- tower runs of CDMS-II at Soudan  

SciTech Connect

Images of the Bullet Cluster of galaxies in visible light, X-rays, and through gravitational lensing confirm that most of the matter in the universe is not composed of any known form of matter. The combined evidence from the dynamics of galaxies and clusters of galaxies, the cosmic microwave background, big bang nucleosynthesis, and other observations indicates that 80% of the universe's matter is dark, nearly collisionless, and cold. The identify of the dar, matter remains unknown, but weakly interacting massive particles (WIMPs) are a very good candidate. They are a natural part of many supersymmetric extensions to the standard model, and could be produced as a nonrelativistic, thermal relic in the early universe with about the right density to account for the missing mass. The dark matter of a galaxy should exist as a spherical or ellipsoidal cloud, called a 'halo' because it extends well past the edge of the visible galaxy. The Cryogenic Dark Matter Search (CDMS) seeks to directly detect interactions between WIMPs in the Milky Way's galactic dark matter halo using crystals of germanium and silicon. Our Z-sensitive ionization and phonon ('ZIP') detectors simultaneously measure both phonons and ionization produced by particle interactions. In order to find very rare, low-energy WIMP interactions, they must identify and reject background events caused by environmental radioactivity, radioactive contaminants on the detector,s and cosmic rays. In particular, sophisticated analysis of the timing of phonon signals is needed to eliminate signals caused by beta decays at the detector surfaces. This thesis presents the firs two dark matter data sets from the deep underground experimental site at the Soudan Underground Laboratory in Minnesota. These are known as 'Run 118', with six detectors (1 kg Ge, 65.2 live days before cuts) and 'Run 119', with twelve detectors (1.5 kg Ge, 74.5 live days before cuts). They have analyzed all data from the two runs together in a single, combined analysis, with sensitivity to lower-energy interactions, careful control of data quality and stability, and further development of techniques for reconstructing event location and rejecting near-surface interactions from beta decays. They also present a revision to the previously published Run 119 analysis, a demonstration of the feasibility of a low-threshold (1 or 2 keV) analysis of Soudan data, and a review of the literature on charge generation and quenching relevant to the ionization signal.

Ogburn, Reuben Walter, IV; /Stanford U., Phys. Dept.

2008-04-01T23:59:59.000Z

74

Search for dark matter candidates and large extra dimensions in events with a jet and missing transverse momentum with the ATLAS detector  

E-Print Network (OSTI)

A search for new phenomena in events with a high-energy jet and large missing transverse momentum is performed using data from proton-proton collisions at sqrt(s)=7 TeV with the ATLAS experiment at the Large Hadron Collider. Four kinematic regions are explored using a dataset corresponding to an integrated luminosity of 4.7 inverse femtobarn. No excess of events beyond expectations from Standard Model processes is observed, and limits are set on large extra dimensions and the pair production of dark matter particles.

The ATLAS Collaboration

2012-10-16T23:59:59.000Z

75

Fake Dark Matter at Colliders  

E-Print Network (OSTI)

If the dark matter (DM) consists of a weakly interacting massive particle (WIMP), it can be produced and studied at future collider experiments like those at the LHC. The production of collider-stable WIMPs is characterized by hard scattering events with large missing transverse energy. Here we point out that the discovery of this well-characterized DM signal may turn out to be a red herring. We explore an alternative explanation -- fake dark matter -- where the only sources of missing transverse energy are standard model neutrinos. We present examples of such models, focusing on supersymmetric models with R-parity violation. We also briefly discuss means of differentiating fake dark matter from the production of new collider-stable particles.

Chang, Spencer

2009-01-01T23:59:59.000Z

76

Fake Dark Matter at Colliders  

E-Print Network (OSTI)

If the dark matter (DM) consists of a weakly interacting massive particle (WIMP), it can be produced and studied at future collider experiments like those at the LHC. The production of collider-stable WIMPs is characterized by hard scattering events with large missing transverse energy. Here we point out that the discovery of this well-characterized DM signal may turn out to be a red herring. We explore an alternative explanation -- fake dark matter -- where the only sources of missing transverse energy are standard model neutrinos. We present examples of such models, focusing on supersymmetric models with R-parity violation. We also briefly discuss means of differentiating fake dark matter from the production of new collider-stable particles.

Spencer Chang; Andre de Gouvea

2009-01-30T23:59:59.000Z

77

Decoupling Dark Energy from Matter  

E-Print Network (OSTI)

We examine the embedding of dark energy in high energy models based upon supergravity and extend the usual phenomenological setting comprising an observable sector and a hidden supersymmetry breaking sector by including a third sector leading to the acceleration of the expansion of the universe. We find that gravitational constraints on the non-existence of a fifth force naturally imply that the dark energy sector must possess an approximate shift symmetry. When exact, the shift symmetry provides an example of a dark energy sector with a runaway potential and a nearly massless dark energy field whose coupling to matter is very weak, contrary to the usual lore that dark energy fields must couple strongly to matter and lead to gravitational inconsistencies. Moreover, the shape of the potential is stable under one-loop radiative corrections. When the shift symmetry is slightly broken by higher order terms in the Kähler potential, the coupling to matter remains small. However, the cosmological dynamics are largely affected by the shift symmetry breaking operators leading to the appearance of a minimum of the scalar potential such that dark energy behaves like an effective cosmological constant from very early on

Carsten Van De Bruck; Jérôme Martin; et al.

2009-01-01T23:59:59.000Z

78

Constraints on inelastic dark matter from XENON10  

SciTech Connect

It has been suggested that dark matter particles which scatter inelastically from detector target nuclei could explain the apparent incompatibility of the DAMA modulation signal (interpreted as evidence for particle dark matter) with the null results from CDMS-II and XENON10. Among the predictions of inelastically interacting dark matter are a suppression of low-energy events, and a population of nuclear recoil events at higher nuclear recoil equivalent energies. This is in stark contrast to the well-known expectation of a falling exponential spectrum for the case of elastic interactions. We present a new analysis of XENON10 dark matter search data extending to E{sub nr} = 75 keV nuclear recoil equivalent energy. Our results exclude a significant region of previously allowed parameter space in the model of inelastically interacting dark matter. In particular, it is found that dark matter particle masses m{sub x} {approx}> 150 GeV are disfavored.

Angle, J; Aprile, E; Arneodo, F; Baudis, L; Bernstein, A; Bolozdynya, A; Coelho, L C; Dahl, C E; DeViveiros, L; Ferella, A D; Fernandes, L P; Fiorucci, S; Gaitskell, R J; Giboni, K L; Gomez, R; Hasty, R; Kastens, L; Kwong, J; Lopes, J M; Madden, N; Manalaysay, A; Manzur, A; McKinsey, D N; Monzani, M E; Ni, K; Oberlack, U; Orboeck, J; Plante, G; Santorelli, R; dos Santos, J; Shagin, P; Shutt, T; Sorensen, P; Schulte, S; Winant, C; Yamashita, M

2009-11-23T23:59:59.000Z

79

Supersymmetry, Dark Matter and the LHC  

Science Conference Proceedings (OSTI)

The conceptually simplest scenario for dark matter (DM) is that it is a stable thermal relic from standard Big Bang cosmology, in many SUSY models the lightest neutralino. The relic density determination selects special regions in SUSY model parameter space with concomitant implications for collider physics, dark matter searches and low energy measurements. By studying various one-parameter extensions of the much-studied mSUGRA model (where we relax the untested universality assumptions) constructed to be in accord with the measured relic density, we show that these implications are in general model-dependent, so that LHC and DM measurements will provide clues to how sparticles acquire their masses. We point out some relatively robust implications for LHC and DM searches and conclude with an outlook for the future.

Tata, Xerxes [Department of Physics and Astronomy, University of Hawaii, Honolulu, HI 96825 (United States) and Physics Department, University of Wisconsin, Madison, WI 53705 (United States)

2010-02-10T23:59:59.000Z

80

The XENON100 Dark Matter Experiment  

SciTech Connect

The XENON100 experiment is searching for WIMPs, which are particles that may consist dark matter. It is located in the underground laboratory of Gran Sasso (LNGS) in Italy at a depth of {approx}3600 m.w.e.. The experiment description, its performance and the expected background based on Monte Carlo simulations and material screening along with the projected sensitivities of the experiment are presented. In addition, a brief description of the upgrade XENON100 detector is given.

Tziaferi, E. [Physics Institute, University of Zuerich, Winterthurerstr. 190, Zuerich (Switzerland)

2010-06-23T23:59:59.000Z

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81

From Dark Energy and Dark Matter to Dark Metric  

E-Print Network (OSTI)

It is nowadays clear that General Relativity cannot be the definitive theory of Gravitation due to several shortcomings that come out both from theoretical and experimental viewpoints. At large scales (astrophysical and cosmological) the attempts to match it with the latest observational data lead to invoke Dark Energy and Dark Matter as the bulk components of the cosmic fluid. Since no final evidence, at fundamental level, exists for such ingredients, it is clear that General Relativity presents shortcomings at infrared scales. On the other hand, the attempts to formulate more general theories than Einstein's one give rise to mathematical difficulties that need workarounds that, in turn, generate problems from the interpretative viewpoint. We present here a completely new approach to the mathematical objects in terms of which a theory of Gravitation may be written in a first-order (a' la Palatini) formalism, and introduce the concept of Dark Metric which could completely bypass the introduction of disturbing concepts as Dark Energy and Dark Matter.

S. Capozziello; M. De Laurentis; M. Francaviglia; S. Mercadante

2008-05-23T23:59:59.000Z

82

Semi-annihilation of dark matter  

E-Print Network (OSTI)

We show that the thermal relic abundance of dark matter can be affected by a new type of reaction: semi-annihilation. Semi-annihilation takes the schematic form ..., where psi i are stable dark matter particles and phi is ...

D’Eramo, Francesco

83

Dark matter axions and caustic rings  

SciTech Connect

This report contains discussions on the following topics: the strong CP problem; dark matter axions; the cavity detector of galactic halo axions; and caustic rings in the density distribution of cold dark matter halos.

Sikivie, P.

1997-11-01T23:59:59.000Z

84

The Dark Side: from Dark Energy & Dark Matter to Washington and Science Policy  

E-Print Network (OSTI)

The Dark Side: from Dark Energy & Dark Matter to Washington and Science Policy Presenter: Michael: The Map Room (www.maproom.com )1949 N. Hoyne #12;The Dark Side: from Dark Energy and Dark Matter to Washington and Science Policy Presenter: Michael S. Turner Time & Date: 7-9 PM Monday June 16, 2008 Location

Collar, Juan I.

85

Direct Detection of Classically Undetectable Dark Matter through Quantum Decoherence  

E-Print Network (OSTI)

Although various pieces of indirect evidence about the nature of dark matter have been collected, its direct detection has eluded experimental searches despite extensive effort. If the mass of dark matter is below 1 MeV, it is essentially imperceptible to conventional detection methods because negligible energy is transferred to nuclei during collisions. Here I propose directly detecting dark matter through the quantum decoherence it causes rather than its classical effects such as recoil or ionization. I show that quantum spatial superpositions are sensitive to low-mass dark matter which is inaccessible to classical techniques. This provides new independent motivation for matter interferometry with large masses, especially on spaceborne platforms. The apparent dark matter wind we experience as the Sun travels through the Milky Way ensures interferometers and related devices are directional detectors, and so are able to provide unmistakable evidence that decoherence has galactic origins.

C. Jess Riedel

2012-12-13T23:59:59.000Z

86

A Search for dark matter in events with one jet and missing transverse energy in $p\\bar{p}$ collisions at $\\sqrt{s} = 1.96$ TeV  

SciTech Connect

We present the results of a search for dark matter production in the monojet signature. We analyze a sample of Tevatron pp collisions at {radical}s = 1.96 TeV corresponding to an integrated luminosity of 6.7 fb{sup -1} recorded by the CDF II detector. In events with large missing transverse energy and one energetic jet, we find good agreement between the standard model prediction and the observed data. We set 90% confidence level upper limits on the dark matter production rate. The limits are translated into bounds on nucleon-dark matter scattering rates which are competitive with current direct detection bounds on spin-independent interaction below a dark matter candidate mass of 5 GeV/c{sup 2}, and on spin-dependent interactions up to masses of 200 GeV/c{sup 2}.

Aaltonen, T.; /Helsinki Inst. of Phys.; Alvarez Gonzalez, B.; /Oviedo U. /Cantabria Inst. of Phys.; Amerio, S.; /INFN, Padua; Amidei, D.; /Michigan U.; Anastassov, A.; /Northwestern U. /Fermilab; Annovi, A.; /Frascati; Antos, J.; /Comenius U.; Apollinari, G.; /Fermilab; Appel, J.A.; /Fermilab; Arisawa, T.; /Waseda U.; Artikov, A.; /Dubna, JINR /Texas A-M

2012-03-01T23:59:59.000Z

87

Baryonic Dark Matter in Galaxies  

E-Print Network (OSTI)

Cosmological nucleosynthesis calculations imply that many of the baryons in the Universe must be dark. We discuss the likelihood that some of these dark baryons may reside in the discs or halos of galaxies. If they were in the form of compact objects, they would then be natural MACHO candidates, in which case they are likely to be the remnants of a first generation of pregalactic or protogalactic Population III stars. Various candidates have been proposed for such remnants - brown dwarfs, red dwarfs, white dwarfs, neutron stars or black holes - and we review the many types of observations (including microlensing searches) which can be used to constrain or exclude them.

B. J. Carr

2000-08-01T23:59:59.000Z

88

Dark matter, dark energy and gravitational proprieties of antimatter  

E-Print Network (OSTI)

We suggest that the eventual gravitational repulsion between matter and antimatter may be a key for understanding of the nature of dark matter and dark energy. If there is gravitational repulsion, virtual particle-antiparticle pairs in the vacuum, may be considered as gravitational dipoles. We use a simple toy model to reveal a first indication that the gravitational polarization of such a vacuum, caused by baryonic matter in a Galaxy, may produce the same effect as supposed existence of dark matter. In addition, we argue that cancellation of gravitational charges in virtual particle-antiparticle pairs, may be a basis for a solution of the cosmological constant problem and identification of dark energy with vacuum energy. Hence, it may be that dark matter and dark energy are not new, unknown forms of matter-energy but an effect of complex interaction between quantum vacuum and known baryonic matter.

Dragan Slavkov Hajdukovic

2008-10-19T23:59:59.000Z

89

Indirect dark matter searches: towards a consistent top-bottom approach for studying the gamma-ray signals and associated backgrounds  

E-Print Network (OSTI)

While dark matter (DM) is the key ingredient for a successful theory of structure formation, its microscopic nature remains elusive. Indirect detection may provide a powerful test for some strongly motivated DM particle models. Nevertheless, astrophysical backgrounds are usually expected with amplitudes and spectral features similar to the chased signals. On galactic scales, these backgrounds arise from interactions of cosmic rays (CRs) with the interstellar gas, both being difficult to infer and model in detail from observations. Moreover, the associated predictions unavoidably come with theoretical errors, which are known to be significant. We show that a trustworthy guide for such challenging searches can be obtained by exploiting the full information contained in cosmological simulations of galaxies, which now include baryonic gas dynamics and star formation. We further insert CR production and transport from the identified supernova events and fully calculate the CR distribution in a simulated galaxy. We focus on diffuse gamma-rays, and self-consistently calculate both the astrophysical galactic emission and the dark matter signal. We notably show that adiabatic contraction does not necessarily induce large signal-to-noise ratios in galactic centers, and could anyway be traced from the astrophysical background itself. We finally discuss how all this may be used as a generic diagnostic tool for galaxy formation.

Emmanuel Nezri; Julien Lavalle; Romain Teyssier

2012-04-18T23:59:59.000Z

90

Wormhole solutions supported by interacting dark matter and dark energy  

E-Print Network (OSTI)

We show that the presence of a nonminimal interaction between dark matter and dark energy may lead to a violation of the null energy condition and to the formation of a configuration with nontrivial topology (a wormhole). In this it is assumed that both dark matter and dark energy satisfy the null energy condition, a violation of which takes place only in the inner high-density regions of the configuration. This is achieved by assuming that, in a high-density environment, a nonminimal coupling function changes its sign in comparison with the case where dark matter and dark energy have relatively low densities which are typical for a cosmological background. For this case, we find regular static, spherically symmetric solutions describing wormholes supported by dark matter nonminimally coupled to dark energy in the form of a quintessence scalar field.

Folomeev, Vladimir

2013-01-01T23:59:59.000Z

91

Wormhole solutions supported by interacting dark matter and dark energy  

E-Print Network (OSTI)

We show that the presence of a nonminimal interaction between dark matter and dark energy may lead to a violation of the null energy condition and to the formation of a configuration with nontrivial topology (a wormhole). In this it is assumed that both dark matter and dark energy satisfy the null energy condition, a violation of which takes place only in the inner high-density regions of the configuration. This is achieved by assuming that, in a high-density environment, a nonminimal coupling function changes its sign in comparison with the case where dark matter and dark energy have relatively low densities which are typical for a cosmological background. For this case, we find regular static, spherically symmetric solutions describing wormholes supported by dark matter nonminimally coupled to dark energy in the form of a quintessence scalar field.

Vladimir Folomeev; Vladimir Dzhunushaliev

2013-08-13T23:59:59.000Z

92

DMTPC: Dark matter detection with directional sensitivity  

E-Print Network (OSTI)

The Dark Matter Time Projection Chamber (DMTPC) experiment uses CF_4 gas at low pressure (0.1 atm) to search for the directional signature of Galactic WIMP dark matter. We describe the DMTPC apparatus and summarize recent results from a 35.7 g-day exposure surface run at MIT. After nuclear recoil cuts are applied to the data, we find 105 candidate events in the energy range 80 - 200 keV, which is consistent with the expected cosmogenic neutron background. Using this data, we obtain a limit on the spin-dependent WIMP-proton cross-section of 2.0 \\times 10^{-33} cm^2 at a WIMP mass of 115 GeV/c^2. This detector is currently deployed underground at the Waste Isolation Pilot Plant in New Mexico.

Battat, J B R; Caldwell, T; Deaconu, C; Dujmic, D; Fedus, W; Fisher, P; Golub, F; Henderson, S; Inglis, A; Kaboth, A; Kohse, G; Lanza, R; Lee, A; Lopez, J; Monroe, J; Sahin, T; Sciolla, G; Skvorodnev, N; Tomita, H; Wellenstein, H; Wolfe, I; Yamamoto, R; Yegoryan, H

2010-01-01T23:59:59.000Z

93

Dark energy from bulk matter  

SciTech Connect

We consider the possibility of getting accelerated expansion and w=-1 crossing in the context of a braneworld cosmological setup, endowed with a bulk energy-momentum tensor. For a given ansatz of the bulk content, we demonstrate that the bulk pressures dominate the dynamics at late times and can lead to accelerated expansion. We also analyze the constraints under which we can get a realistic profile for the effective equation of state and conclude that matter in the bulk has the effect of dark energy on the brane. Furthermore, we show that it is possible to simulate the behavior to a Chaplygin gas using nonexotic bulk matter.

Bogdanos, C.; Dimitriadis, A.; Tamvakis, K. [Physics Department, University of Ioannina, Ioannina GR451 10 (Greece)

2007-04-15T23:59:59.000Z

94

Dark Energy and Dark Matter as Inertial Effects  

E-Print Network (OSTI)

A globally rotating model of the universe is postulated. It is shown that dark energy and dark matter are cosmic inertial effects resulting from such a cosmic rotation, corresponding to centrifugal and a combination of centrifugal and the Coriolis forces, respectively. The physics and the cosmological and galactic parameters obtained from the model closely match those attributed to dark energy and dark matter in the standard {\\Lambda}-CDM model.

Serkan Zorba

2012-10-10T23:59:59.000Z

95

Indirect dark matter searches: towards a consistent top-bottom approach for studying the gamma-ray signals and associated backgrounds  

E-Print Network (OSTI)

While dark matter (DM) is the key ingredient for a successful theory of structure formation, its microscopic nature remains elusive. Indirect detection may provide a powerful test for some strongly motivated DM particle models. Nevertheless, astrophysical backgrounds are usually expected with amplitudes and spectral features similar to the chased signals. On galactic scales, these backgrounds arise from interactions of cosmic rays (CRs) with the interstellar gas, both being difficult to infer and model in detail from observations. Moreover, the associated predictions unavoidably come with theoretical errors, which are known to be significant. We show that a trustworthy guide for such challenging searches can be obtained by exploiting the full information contained in cosmological simulations of galaxies, which now include baryonic gas dynamics and star formation. We further insert CR production and transport from the identified supernova events and fully calculate the CR distribution in a simulated galaxy. We...

Nezri, Emmanuel; Teyssier, Romain

2012-01-01T23:59:59.000Z

96

Gravitation and regular Universe without dark energy and dark matter  

E-Print Network (OSTI)

It is shown that isotropic cosmology in the Riemann-Cartan spacetime allows to solve the problem of cosmological singularity as well as the problems of invisible matter components - dark energy and dark matter. All cosmological models filled with usual gravitating matter satisfying energy dominance conditions are regular with respect to energy density, spacetime metrics and the Hubble parameter. At asymptotics cosmological solutions of spatially flat models describe accelerating Universe without dark energy and dark matter, and quantitatively their behaviour is identical to that of standard cosmological \\Lambda CDM-model.

A. V. Minkevich

2011-02-03T23:59:59.000Z

97

The Cosmology of Composite Inelastic Dark Matter  

SciTech Connect

Composite dark matter is a natural setting for implementing inelastic dark matter - the O(100 keV) mass splitting arises from spin-spin interactions of constituent fermions. In models where the constituents are charged under an axial U(1) gauge symmetry that also couples to the Standard Model quarks, dark matter scatters inelastically off Standard Model nuclei and can explain the DAMA/LIBRA annual modulation signal. This article describes the early Universe cosmology of a minimal implementation of a composite inelastic dark matter model where the dark matter is a meson composed of a light and a heavy quark. The synthesis of the constituent quarks into dark hadrons results in several qualitatively different configurations of the resulting dark matter composition depending on the relative mass scales in the system.

Spier Moreira Alves, Daniele; Behbahani, Siavosh R.; /SLAC /Stanford U., ITP; Schuster, Philip; Wacker, Jay G.; /SLAC

2011-08-19T23:59:59.000Z

98

Cosmological Evolution With Interaction Between Dark Energy And Dark Matter  

E-Print Network (OSTI)

In this review we consider in detail different theoretical topics associated with interaction in the dark sector. We study linear and nonlinear interactions which depend on the dark matter and dark energy densities. We consider a number of different models (including the holographic dark energy and dark energy in a fractal universe) with interacting dark energy (DE) and dark matter (DM), have done a thorough analysis of these models. The main task of this review was not only to give an idea about the modern set of different models of dark energy, but to show how much can be diverse dynamics of the universe in these models. We find that the dynamics of a Universe that contains interaction in the dark sector can differ significantly from the Standard Cosmological Model (SCM).

Bolotin, Yu L; Lemets, O A; Yerokhin, D A

2013-01-01T23:59:59.000Z

99

EXTRAGALACTIC DARK MATTER AND DIRECT DETECTION EXPERIMENTS  

SciTech Connect

Recent astronomical data strongly suggest that a significant part of the dark matter content of the Local Group and Virgo Supercluster is not incorporated into the galaxy halos and forms diffuse components of these galaxy clusters. A portion of the particles from these components may penetrate the Milky Way and make an extragalactic contribution to the total dark matter containment of our Galaxy. We find that the particles of the diffuse component of the Local Group are apt to contribute {approx}12% to the total dark matter density near Earth. The particles of the extragalactic dark matter stand out because of their high speed ({approx}600 km s{sup -1}), i.e., they are much faster than the galactic dark matter. In addition, their speed distribution is very narrow ({approx}20 km s{sup -1}). The particles have an isotropic velocity distribution (perhaps, in contrast to the galactic dark matter). The extragalactic dark matter should provide a significant contribution to the direct detection signal. If the detector is sensitive only to the fast particles (v > 450 km s{sup -1}), then the signal may even dominate. The density of other possible types of the extragalactic dark matter (for instance, of the diffuse component of the Virgo Supercluster) should be relatively small and comparable with the average dark matter density of the universe. However, these particles can generate anomaly high-energy collisions in direct dark matter detectors.

Baushev, A. N., E-mail: baushev@gmail.com [DESY, D-15738 Zeuthen (Germany); Institut fuer Physik und Astronomie, Universitaet Potsdam, D-14476 Potsdam-Golm (Germany)

2013-07-10T23:59:59.000Z

100

Design and Construction of Prototype Dark Matter Detectors  

SciTech Connect

The Lepton Quark Studies (LQS) group is engaged in searching for dark matter using the Dark Matter Time Projection Chamber (DMTPC) at the Waste Isolation Pilot Plant (WIPP) (Carlsbad, NM). DMTPC is a direction-sensitive dark matter detector designed to measure the recoil direction and energy deposited by fluorine nuclei recoiling from the interaction with incident WIMPs. In the past year, the major areas of progress have been: #15; to publish the #12;first dark matter search results from a surface run of the DMTPC prototype detector, #15; to build and install the 10L prototype in the underground laboratory at WIPP which will house the 1 m{sup 3} detector, and #15; to demonstrate charge and PMT readout of the TPC using prototype detectors, which allow triggering and #1;{Delta}z measurement to be used in the 1 m{sup 3} detector under development.

Peter Fisher

2012-03-23T23:59:59.000Z

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101

An Overview of Dark Matter Experiments at Jefferson Lab  

Science Conference Proceedings (OSTI)

Dark Matter research at Jefferson Lab started in 2006 with the LIght Pseudoscalar and Scalar Search (LIPSS) collaboration to check the validity of results reported by the PVLAS collaboration. In the intervening years interest in dark matter laboratory experiments has grown at Jefferson Lab. Current research underway or in planning stages probe various mass regions covering 14 orders of magnitude: from 10{sup -6} eV to 100 MeV. This presentation will be an overview of our dark matter efforts, three of which focus on the hypothesized A' gauge boson.

James Boyce

2012-09-01T23:59:59.000Z

102

Dark energy, dark matter and the Chaplygin gas  

E-Print Network (OSTI)

The possibility that the dark energy may be described by the Chaplygin gas is discussed. Some observational constraints are established. These observational constraints indicate that a unified model for dark energy and dark matter through the employement of the Chaplygin gas is favored.

R. Colistete Jr.; J. C. Fabris; S. V. B. Goncalves; P. E. de Souza

2002-10-23T23:59:59.000Z

103

Dark matter chaos in the Solar System  

E-Print Network (OSTI)

We study the capture of galactic dark matter particles in the Solar System produced by rotation of Jupiter. It is shown that the capture cross section is much larger than the area of Jupiter orbit being inversely diverging at small particle energy. We show that the dynamics of captured particles is chaotic and is well described by a simple symplectic dark map. This dark map description allows to simulate the scattering and dynamics of $10^{14}$ dark matter particles during the life time of the Solar System and to determine dark matter density profile as a function of distance from the Sun. The mass of captured dark matter in the radius of Neptune orbit is estimated to be $2 \\cdot 10^{15} g$. The radial density of captured dark matter is found to be approximately constant behind Jupiter orbit being similar to the density profile found in galaxies.

J. Lages; D. L. Shepelyansky

2012-11-05T23:59:59.000Z

104

Turning off the lights: How dark is dark matter?  

SciTech Connect

We consider current observational constraints on the electromagnetic charge of dark matter. The velocity dependence of the scattering cross section through the photon gives rise to qualitatively different constraints than standard dark matter scattering through massive force carriers. In particular, recombination epoch observations of dark matter density perturbations require that {epsilon}, the ratio of the dark matter to electronic charge, is less than 10{sup -6} for m{sub X}=1 GeV, rising to {epsilon}<10{sup -4} for m{sub X}=10 TeV. Though naively one would expect that dark matter carrying a charge well below this constraint could still give rise to large scattering in current direct detection experiments, we show that charged dark matter particles that could be detected with upcoming experiments are expected to be evacuated from the Galactic disk by the Galactic magnetic fields and supernova shock waves and hence will not give rise to a signal. Thus dark matter with a small charge is likely not a source of a signal in current or upcoming dark matter direct detection experiments.

McDermott, Samuel D.; Yu Haibo; Zurek, Kathryn M. [Michigan Center for Theoretical Physics, Department of Physics, University of Michigan, Ann Arbor, Michigan 48109 (United States)

2011-03-15T23:59:59.000Z

105

Cluster number counts dependence on dark energy inhomogeneities and coupling to dark matter  

E-Print Network (OSTI)

Cluster number counts can be used to test dark energy models. We investigate dark energy candidates which are coupled to dark matter. We analyze the cluster number counts dependence on the amount of dark matter coupled to dark energy. Further

M. Manera; D. F. Mota

2006-01-01T23:59:59.000Z

106

TASI 2008 Lectures on Dark Matter  

SciTech Connect

Based on lectures given at the 2008 Theoretical Advanced Study Institute (TASI), I review here some aspects of the phenomenology of particle dark matter, including the process of thermal freeze-out in the early universe, and the direct and indirect detection of WIMPs. I also describe some of the most popular particle candidates for dark matter and summarize the current status of the quest to discover dark matter's particle identity.

Hooper, Dan; /Fermilab /Chicago U., Astron. Astrophys. Ctr.

2009-01-01T23:59:59.000Z

107

Dark atoms of dark matter from new stable quarks and leptons  

SciTech Connect

The nonbaryonic dark matter of the Universe can consist of new stable charged leptons and quarks, if they are hidden in elusive 'dark atoms' of composite dark matter. Such possibility can be compatible with the severe constraints on anomalous isotopes, if there exist stable particles with charge -2 and there are no stable particles with charges +1 and -1. These conditions cannot be realized in supersymmetric models, but can be satisfied in several recently developed alternative scenarios. The excessive -2 charged particles are bound with primordial helium in O-helium 'atoms', maintaining specific nuclear-interacting form of the Warmer than Cold Dark Matter. The puzzles of direct dark matter searches appear in this case as a reflection of nontrivial nuclear physics of O-helium.

Khlopov, Maxim Yu. [APC laboratory 10, rue Alice Domon et Leonie Duquet, 75205 Paris Cedex 13 (France)

2012-06-20T23:59:59.000Z

108

Some Practical Applications of Dark Matter Research  

E-Print Network (OSTI)

Two practical spin-offs from the development of cryogenic dark matter detectors are presented. One in materials research, the other in biology.

Stodolsky, L

2008-01-01T23:59:59.000Z

109

Unified Dark Energy-Dark Matter model with Inverse Quintessence  

E-Print Network (OSTI)

We consider a model where both dark energy and dark matter originate from the coupling of a scalar field with a non-conventional kinetic term to, both, a metric measure and a non-metric measure. An interacting dark energy/dark matter scenario can be obtained by introducing an additional scalar that can produce non constant vacuum energy and associated variations in dark matter. The phenomenology is most interesting when the kinetic term of the additional scalar field is ghost-type, since in this case the dark energy vanishes in the early universe and then grows with time. This constitutes an "inverse quintessence scenario", where the universe starts from a zero vacuum energy density state, instead of approaching it in the future.

Stefano Ansoldi; Eduardo I. Guendelman

2012-09-21T23:59:59.000Z

110

Composite dark matter from a model with composite Higgs boson  

E-Print Network (OSTI)

In a previous paper \\cite{Khlopov:2007ic}, we showed how the minimal walking technicolor model (WTC) can provide a composite dark matter candidate, by forming bound states between a -2 electrically charged techniparticle and a $^4He^{++}$. We studied the properties of these \\emph{techni-O-helium} $tOHe$ "atoms", which behave as warmer dark matter rather than cold. In this paper we extend our work on several different aspects. We study the possibility of a mixed scenario where both $tOHe$ and bound states between +2 and -2 electrically charged techniparticles coexist in the dark matter density. We argue that these newly proposed bound states solely made of techniparticles, although they behave as Weakly Interacting Massive Particles (WIMPs), due to their large elastic cross section with nuclei, can only account for a small percentage of the dark matter density. Therefore we conclude that within the minimal WTC, composite dark matter should be mostly composed of $tOHe$. Moreover in this paper, we put cosmological bounds in the masses of the techniparticles, if they compose the dark matter density. Finally we propose within this setup, a possible explanation of the discrepancy between the DAMA/NaI and DAMA/LIBRA findings and the negative results of CDMS and other direct dark matter searches that imply nuclear recoil measurement, which should accompany ionization.

Maxim Yu. Khlopov; Chris Kouvaris

2008-06-06T23:59:59.000Z

111

Singlet-Doublet Dark Matter  

Science Conference Proceedings (OSTI)

In light of recent data from direct detection experiments and the Large Hadron Collider, we explore models of dark matter in which an SU(2){sub L} doublet is mixed with a Standard Model singlet. We impose a thermal history. If the new particles are fermions, this model is already constrained due to null results from XENON100. We comment on remaining regions of parameter space and assess prospects for future discovery. We do the same for the model where the new particles are scalars, which at present is less constrained. Much of the remaining parameter space for both models will be probed by the next generation of direct detection experiments. For the fermion model, DeepCore may also play an important role.

Cohen, Timothy; /SLAC /Michigan U., MCTP; Kearney, John; Pierce, Aaron; /Michigan U., MCTP; Tucker-Smith, David; /Williams Coll.

2012-02-15T23:59:59.000Z

112

Dark Matter in the Coming Decade: Complementary Paths to Discovery and Beyond  

E-Print Network (OSTI)

In this report we summarize the many dark matter searches currently being pursued through four complementary approaches: direct detection, indirect detection, collider experiments, and astrophysical probes. The essential features of broad classes of experiments are described, each with their own strengths and weaknesses. The complementarity of the different dark matter searches is discussed qualitatively and illustrated quantitatively in two simple theoretical frameworks. Our primary conclusion is that the diversity of possible dark matter candidates requires a balanced program drawing from all four approaches.

Daniel Bauer; James Buckley; Matthew Cahill-Rowley; Randel Cotta; Alex Drlica-Wagner; Jonathan Feng; Stefan Funk; JoAnne Hewett; Dan Hooper; Ahmed Ismail; Manoj Kaplinghat; Alexander Kusenko; Konstantin Matchev; Daniel McKinsey; Tom Rizzo; William Shepherd; Tim M. P. Tait; Alexander M. Wijangco; Matthew Wood

2013-05-07T23:59:59.000Z

113

Antigravitation, Dark Energy, Dark Matter - Alternative Solution  

E-Print Network (OSTI)

Collisional damping of gravitational waves in the Newtonian matter is investigated. The generalized theory of Landau damping is applied to the gravitational physical systems in the context of the plasma gravitational analogy.

Alexeev, Boris V

2009-01-01T23:59:59.000Z

114

Antigravitation, Dark Energy, Dark Matter - Alternative Solution  

E-Print Network (OSTI)

Collisional damping of gravitational waves in the Newtonian matter is investigated. The generalized theory of Landau damping is applied to the gravitational physical systems in the context of the plasma gravitational analogy.

Boris V. Alexeev

2009-08-15T23:59:59.000Z

115

Development and Performance of Detectors for the Cryogenic Dark Matter Search Experiment with an Increased Sensitivity Based on a Maximum Likelihood Analysis of Beta Contamination  

Science Conference Proceedings (OSTI)

The Cryogenic Dark Matter Search (CDMS) uses cryogenically-cooled detectors made of germanium and silicon in an attempt to detect dark matter in the form of Weakly-Interacting Massive Particles (WIMPs). The expected interaction rate of these particles is on the order of 1/kg/day, far below the 200/kg/day expected rate of background interactions after passive shielding and an active cosmic ray muon veto. Our detectors are instrumented to make a simultaneous measurement of both the ionization energy and thermal energy deposited by the interaction of a particle with the crystal substrate. A comparison of these two quantities allows for the rejection of a background of electromagnetically-interacting particles at a level of better than 99.9%. The dominant remaining background at a depth of {approx} 11 m below the surface comes from fast neutrons produced by cosmic ray muons interacting in the rock surrounding the experiment. Contamination of our detectors by a beta emitter can add an unknown source of unrejected background. In the energy range of interest for a WIMP study, electrons will have a short penetration depth and preferentially interact near the surface. Some of the ionization signal can be lost to the charge contacts there and a decreased ionization signal relative to the thermal signal will cause a background event which interacts at the surface to be misidentified as a signal event. We can use information about the shape of the thermal signal pulse to discriminate against these surface events. Using a subset of our calibration set which contains a large fraction of electron events, we can characterize the expected behavior of surface events and construct a cut to remove them from our candidate signal events. This thesis describes the development of the 6 detectors (4 x 250 g Ge and 2 x 100 g Si) used in the 2001-2002 CDMS data run at the Stanford Underground Facility with a total of 119 livedays of data. The preliminary results presented are based on the first use of a beta-eliminating cut based on a maximum-likelihood characterization described above.

Driscoll, Donald D.; /Case Western Reserve U.

2004-01-01T23:59:59.000Z

116

UNIFYING DARK ENERGY AND DARK MATTER WITH A SCALAR FIELD  

E-Print Network (OSTI)

Abstract. The standard model of cosmology considers the existence of two components of unknown nature, “dark matter ” and “dark energy”, which determine the cosmological evolution. Their nature remains unknown, and other models can also be considered. In particular, it may be possible to reinterpret the recent cosmological observations so that the Universe does not contain two fluids of unknown natures, but only one fluid with particular properties. After a brief review of constraints on this unifying “dark fluid”, we will discuss a specific model of dark fluid based on a complex scalar fluid. 1

G. Mamon; F. Combes; C. Deffayet; B. Fort (eds; Arbey A

2005-01-01T23:59:59.000Z

117

Dark Matter in the Private Higgs Model  

E-Print Network (OSTI)

The extremely large hierarchy observed in the fermion mass spectrum remains as one of the most puzzling and unresolved issues in particle physics. In a recent proposal, however, it was demonstrated that by introducing one Higgs doublet (or Private Higgs) per fermion this hierarchy could be made natural by making the Yukawa couplings between each fermion and its respective Higgs boson of order unity. Among the interesting predictions of the Private Higgs scenario is a variety of scalars which could be probed at future collider experiments and a possible dark matter candidate. In this paper, we study in some detail the dark matter sector of the Private Higgs model. We first calculate the annihilation cross sections of dark matter in this model and find that one can easily account for the observed density of dark matter in the Universe with relatively natural values of the model's parameters. Finally, we investigate the possibility of detecting Private Higgs dark matter indirectly via the observation of anomalous gamma rays originating from the galactic halo. We show that a substantial flux of photons can be produced from the annihilation of Private Higgs dark matter such that, if there is considerable clumping of dark matter in the galactic halo, the flux of these gamma rays could be observed by ground-based telescope arrays such as VERITAS and HESS.

C. B. Jackson

2008-04-23T23:59:59.000Z

118

A Search for Dark Higgs Bosons  

SciTech Connect

Recent astrophysical and terrestrial experiments have motivated the proposal of a dark sector with GeV-scale gauge boson force carriers and new Higgs bosons. We present a search for a dark Higgs boson using 516 fb{sup -1} of data collected with the BABAR detector. We do not observe a significant signal and we set 90% confidence level upper limits on the product of the Standard Model-dark sector mixing angle and the dark sector coupling constant.

Lees, J.P.

2012-06-08T23:59:59.000Z

119

SOLAR CONSTRAINTS ON ASYMMETRIC DARK MATTER  

SciTech Connect

The dark matter content of the universe is likely to be a mixture of matter and antimatter, perhaps comparable to the measured asymmetric mixture of baryons and antibaryons. During the early stages of the universe, the dark matter particles are produced in a process similar to baryogenesis, and dark matter freezeout depends on the dark matter asymmetry and the annihilation cross section (s-wave and p-wave annihilation channels) of particles and antiparticles. In these {eta}-parameterized asymmetric dark matter ({eta}ADM) models, the dark matter particles have an annihilation cross section close to the weak interaction cross section, and a value of dark matter asymmetry {eta} close to the baryon asymmetry {eta}{sub B}. Furthermore, we assume that dark matter scattering of baryons, namely, the spin-independent scattering cross section, is of the same order as the range of values suggested by several theoretical particle physics models used to explain the current unexplained events reported in the DAMA/LIBRA, CoGeNT, and CRESST experiments. Here, we constrain {eta}ADM by investigating the impact of such a type of dark matter on the evolution of the Sun, namely, the flux of solar neutrinos and helioseismology. We find that dark matter particles with a mass smaller than 15 GeV, a spin-independent scattering cross section on baryons of the order of a picobarn, and an {eta}-asymmetry with a value in the interval 10{sup -12}-10{sup -10}, would induce a change in solar neutrino fluxes in disagreement with current neutrino flux measurements. This result is also confirmed by helioseismology data. A natural consequence of this model is suppressed annihilation, thereby reducing the tension between indirect and direct dark matter detection experiments, but the model also allows a greatly enhanced annihilation cross section. All the cosmological {eta}ADM scenarios that we discuss have a relic dark matter density {Omega}h {sup 2} and baryon asymmetry {eta}{sub B} in agreement with the current WMAP measured values, {Omega}{sub DM} h {sup 2} = 0.1109 {+-} 0.0056 and {eta}{sub B} = 0.88 Multiplication-Sign 10{sup -10}.

Lopes, Ilidio [Centro Multidisciplinar de Astrofisica, Instituto Superior Tecnico, Universidade Tecnica de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Silk, Joseph, E-mail: ilidio.lopes@ist.utl.pt, E-mail: silk@astro.ox.ac.uk [Institut d'Astrophysique de Paris, F-75014 Paris (France)

2012-10-01T23:59:59.000Z

120

RESULTS FROM THE CHANDRA MULTIVERSE. III. THE PHYSICAL NATURE OF DARK MATTER AND DARK ENERGY  

E-Print Network (OSTI)

RESULTS FROM THE CHANDRA MULTIVERSE. III. THE PHYSICAL NATURE OF DARK MATTER AND DARK ENERGY TOM ABSTRACT This paper solves the dark-matter and dark-energy problem by taking into account that our universe because there already are theoretical studies of them as dark matter. Dark energy has been used

Gehrels, Tom

Note: This page contains sample records for the topic "dark matter searches" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


121

Dark Photon Search at BABAR  

SciTech Connect

Presented is the current progress of a search for the signature of a dark photon or new particle using the BaBar data set. We search for the processes e{sup +}e{sup -} {yields} {gamma}{sub ISR}A{prime},A{prime} {yields} e{sup +}e{sup -} and e{sup +}e{sup -} {yields} {gamma}{sub ISR}{gamma}, {gamma} {yields} A{prime},A{prime} {yields} e{sup +}e{sup -}, where {gamma}{sub ISR} is an initial state radiated photon of energy E{sub {gamma}} >= 1 GeV. Twenty-five sets of Monte Carlo, simulating e{sup +}e{sup -} collisions at an energy of 10.58 GeV, were produced with different values of the A{prime} mass ranging from 100 MeV to 9.5 GeV. The mass resolution is calculated based on Monte Carlo simulations. We implement ROOT's Toolkit for Multivariate Analysis (TMVA), a machine learning tool that allows us to evaluate the signal character of events based on many of discriminating variables. TMVA training is conducted with samples of Monte Carlo as signal and a small portion of Run 6 as background. The multivariate analysis produces additional cuts to separate signal and background. The signal efficiency and sensitivity are calculated. The analysis will move forward to fit the background and scan the residuals for the narrow resonance peak of a new particle.

Greenwood, Ross N; /MIT /SLAC

2012-09-07T23:59:59.000Z

122

Light Dark Matter Annihilations into Two Photons  

E-Print Network (OSTI)

We compute the pair annihilation cross section of light (spin-0) dark matter particles into two photons and discuss the detectability of the monochromatic line associated with these annihilations.

C. Boehm; J. Orloff; P. Salati

2006-07-19T23:59:59.000Z

123

Hierarchical phase space structure of dark matter haloes: Tidal debris, caustics, and dark matter annihilation  

E-Print Network (OSTI)

Most of the mass content of dark matter haloes is expected to be in the form of tidal debris. The density

Bertschinger, Edmund

124

Measuring the dark matter equation of state  

E-Print Network (OSTI)

The nature of the dominant component of galaxies and clusters remains unknown. While the astrophysics community supports the cold dark matter (CDM) paradigm as a clue factor in the current cosmological model, no direct CDM detections have been performed. Faber and Visser 2006 have suggested a simple method for measuring the dark matter equation of state that combines kinematic and gravitational lensing data to test the widely adopted assumption of pressureless dark matter. Following this formalism, we have measured the dark matter equation of state for first time using improved techniques. We have found that the value of the equation of state parameter is consistent with pressureless dark matter within the errors. Nevertheless, the measured value is lower than expected because typically the masses determined with lensing are larger than those obtained through kinematic methods. We have tested our techniques using simulations and we have also analyzed possible sources of error that could invalidate or mimic our results. In the light of this result, we can now suggest that the understanding of the nature of dark matter requires a complete general relativistic analysis.

Ana Laura Serra; Mariano Javier de León Domínguez Romero

2011-03-28T23:59:59.000Z

125

Fluid Mechanics Explains Cosmology, Dark Matter, Dark Energy, and Life  

E-Print Network (OSTI)

Observations of the interstellar medium by the Herschel, Planck etc. infrared satellites throw doubt on standard {\\Lambda}CDMHC cosmological processes to form gravitational structures. According to the Hydro-Gravitational-Dynamics (HGD) cosmology of Gibson (1996), and the quasar microlensing observations of Schild (1996), the dark matter of galaxies consists of Proto-Globular-star-Cluster (PGC) clumps of Earth-mass primordial gas planets in metastable equilibrium since PGCs began star production at 0.3 Myr by planet mergers. Dark energy and the accelerating expansion of the universe inferred from SuperNovae Ia are systematic dimming errors produced as frozen gas dark matter planets evaporate to form stars. Collisionless cold dark matter that clumps and hierarchically clusters does not exist. Clumps of PGCs began diffusion from the Milky Way Proto-Galaxy upon freezing at 14 Myr to give the Magellanic Clouds and the faint dwarf galaxies of the 10^22 m diameter baryonic dark matter Galaxy halo. The first stars persist as old globular star clusters (OGCs). Water oceans and the biological big bang occurred at 2-8 Myr. Life inevitably formed and evolved in the cosmological primordial organic soup provided by 10^80 big bang planets and their hot oceans as they gently merged to form larger binary planets and small binary stars.

Carl H. Gibson

2012-11-02T23:59:59.000Z

126

Chance and Chandra (and repulsive dark matter)  

E-Print Network (OSTI)

A few examples are given of Chandra's work on statistical and stochastic problems that relate to open questions in astrophysics, in particular his theory of dynamical relaxation in systems with inverse-square interparticle forces. The roles of chaos and integrability in this theory require clarification, especially for systems having a dominant central mass. After this prelude, a hypothetical form of repulsive bosonic dark matter is discussed. The repulsion leads to nontrivial thermodynamic behavior, including superfluidity, and would tend to suppress dynamical friction, greatly reducing the drag exerted on rotating galactic bars. However, this form of dark matter can probably be ruled out, at least for parameters that allow halos to reach thermal equilibria within a Hubble time. One combination of the particle mass and interparticle repulsion determines the minimum core radius of dark halos. Bounds on dark-matter collisionality inferred from the Bullet Cluster constrain a second combination. It is possible t...

Goodman, Jeremy

2011-01-01T23:59:59.000Z

127

The Unification and Cogeneration of Dark Matter and Baryonic Matter  

E-Print Network (OSTI)

In grand unified theories with gauge groups larger than SU(5), the multiplets that contain the known quarks and leptons also contain fermions that are singlets under the Standard Model gauge group. Some of these could be the dark matter of the universe. Grand unified theories can also have accidental U(1) global symmetries (analogous to B-L in minimal SU(5)) that can stabilize dark matter. These ideas are illustrated in an SU(6) model.

S. M. Barr

2011-09-12T23:59:59.000Z

128

The Unification and Cogeneration of Dark Matter and Baryonic Matter  

E-Print Network (OSTI)

In grand unified theories with gauge groups larger than SU(5), the multiplets that contain the known quarks and leptons also contain fermions that are singlets under the Standard Model gauge group. Some of these could be the dark matter of the universe. Grand unified theories can also have accidental U(1) global symmetries (analogous to B-L in minimal SU(5)) that can stabilize dark matter. These ideas are illustrated in an SU(6) model.

Barr, S M

2011-01-01T23:59:59.000Z

129

Non-relativistic effective theory of dark matter direct detection  

E-Print Network (OSTI)

Dark matter direct detection searches for signals coming from dark matter scattering against nuclei at a very low recoil energy scale ~ 10 keV. In this paper, a simple non-relativistic effective theory is constructed to describe interactions between dark matter and nuclei without referring to any underlying high energy models. It contains the minimal set of operators that will be tested by direct detection. The effective theory approach highlights the set of distinguishable recoil spectra that could arise from different theoretical models. If dark matter is discovered in the near future in direct detection experiments, a measurement of the shape of the recoil spectrum will provide valuable information on the underlying dynamics. We bound the coefficients of the operators in our non-relativistic effective theory by the null results of current dark matter direct detection experiments. We also discuss the mapping between the non-relativistic effective theory and field theory models or operators, including aspects of the matching of quark and gluon operators to nuclear form factors.

JiJi Fan; Matthew Reece; Lian-Tao Wang

2010-08-09T23:59:59.000Z

130

BABAR Constrains Dark-Matter Photon and Higgs  

NLE Websites -- All DOE Office Websites (Extended Search)

Constrains Dark-Matter Photon and Higgs The majority of matter in the universe is "dark matter" that does not interact with light. Since it cannot be seen directly, its existence...

131

astro-ph/0212275 Dark Group: Dark Energy and Dark Matter  

E-Print Network (OSTI)

We study the possibility that a dark group, a gauge group with particles interacting with the standard model particles only via gravity, is responsible for containing the dark energy and dark matter required by present day observations. We show that it is indeed possible and we determine the constrains for the dark group. The non-perturbative effects generated by a strong gauge coupling constant can de determined and a scalar potential for the dark meson fields is generated parameterizing the dark energy. On the other hand it is the massive particles, e.g. dark baryons, of the dark gauge group that give the corresponding dark matter. The mass of the dark particles is of the order of the condensation scale ?c and the temperature is 4-5 times smaller then the photon’s temperature. The dark matter is of the warm matter type and it gives good fit to structure formation. The only parameters of the model are the number of particles of the dark group. The conditions to not introduce any fine tuning of the energy density at the condensation scale plus the CMB spectrum constrains the condensation scale to 0.2 eV dark matter with mass m = 42eV, a temperature TDM = T?/4.85 and a free streaming scale ?fs = 1.6Mpc with a contain mass M = 4 × 10 11 M ? (M ? is the solar mass). The dark energy has an equation of state parameter today wo = ?0.9 and the model agrees well with the CMB data. The cosmological observations are pushing the condensation scale to an epoch close to radiation and matter equality and this late time phase transition is the reason why the universe is accelerating at present time. 1

A. De La Macorra

2002-01-01T23:59:59.000Z

132

The Top Window for dark matter  

E-Print Network (OSTI)

We investigate a scenario that the top quark is the only window to the dark matter particle. We use the effective Lagrangian approach to write down the interaction between the top quark and the dark matter particle. Requiring the dark matter satisfying the relic density we obtain the size of the effective interaction. We show that the scenario can be made consistent with the direct and indirect detection experiments by adjusting the size of the effective coupling. Finally, we calculate the production cross section for $t\\bar t + \\chi \\bar \\chi$ at the Large Hadron Collider (LHC), which will give rise to an interesting signature of a top-pair plus large missing energy.

Kingman Cheung; Kentarou Mawatari; Eibun Senaha; Po-Yan Tseng; Tzu-Chiang Yuan

2010-09-03T23:59:59.000Z

133

MODELING OBSERVATIONAL CONSTRAINTS FOR DARK MATTER HALOS  

SciTech Connect

Observations show that the underlying rotation curves at intermediate radii in spiral and low-surface-brightness galaxies are nearly universal. Further, in these same galaxies, the product of the central density and the core radius ({rho}{sub 0} r{sub 0}) is constant. An empirically motivated model for dark matter halos that incorporates these observational constraints is presented and shown to be in accord with the observations. A model fit to the observations of the galaxy cluster A611 shows that {rho}{sub 0} r{sub 0} for the dark matter halo in this more massive structure is larger by a factor of {approx}20 over that assumed for the galaxies. The model maintains the successful Navarro-Frenk-White form in the outer regions, although the well-defined differences in the inner regions suggest that modifications to the standard cold dark matter picture are required.

Hartwick, F. D. A. [Department of Physics and Astronomy, University of Victoria, Victoria, BC V8W 3P6 (Canada)

2012-12-01T23:59:59.000Z

134

Holographic dark matter and dark energy with second order invariants  

E-Print Network (OSTI)

One of the main goals of modern cosmology remains to summon up a self consistent policy, able to explain, in the framework of the Einstein's theory, the cosmic speed up and the presence of Dark Matter in the Universe. Accordingly to the Holographic principle, which postulates the existence of a minimal size of a physical region, we argue, in this paper, that if this size exists for the Universe and it is accrued from the independent geometrical second order invariants, it would be possible to ensure a surprising source for Dark Matter and a viable candidate for explaining the late acceleration of the Universe. Along the work, we develop low redshift tests, such as Supernovae Ia and kinematical analysis complied by the use of Cosmography and we compare the outcomes with higher redshift tests, such as CMB peak and anisotropy of the cosmic power spectrum. All the results indicate that the models presented here can be interpreted as unified models that are capable to describe both the dark matter and the dark energy.

Alejandro Aviles; Luca Bonanno; Orlando Luongo; Hernando Quevedo

2011-09-14T23:59:59.000Z

135

A dark matter model with non-Abelian gauge symmetry.  

SciTech Connect

We propose a dark-matter model in which the dark sector is gauged under a new SU(2) group. The dark sector consists of SU(2) dark gauge fields, two triplet dark Higgs fields, and two dark fermion doublets (dark-matter candidates in this model). The dark sector interacts with the standard model sector through kinetic and mass mixing operators. The model explains both PAMELA and Fermi LAT data very well and also satisfies constraints from both the dark-matter relic density and standard model precision observables. The phenomenology of the model at the LHC is also explored.

Zhang, H.; Li, C. S.; Cao, Q.-H.; Li, Z.; High Energy Physics; Univ. of Chicago; Peking Univ.; Michigan State Univ.

2010-10-07T23:59:59.000Z

136

Gamma-Ray Bursts and Dark Energy - Dark Matter interaction  

E-Print Network (OSTI)

In this work Gamma Ray Burst (GRB) data is used to place constraints on a putative coupling between dark energy and dark matter. Type Ia supernovae (SNe Ia) constraints from the Sloan Digital Sky Survey II (SDSS-II) first-year results, the cosmic microwave background radiation (CMBR) shift parameter from WMAP seven year results and the baryon acoustic oscillation (BAO) peak from the Sloan Digital Sky Survey (SDSS) are also discussed. The prospects for the field are assessed, as more GRB events become available.

T. Barreiro; O. Bertolami; P. Torres

2010-04-26T23:59:59.000Z

137

A Critique of Drexler Dark Matter  

E-Print Network (OSTI)

Drexler dark matter is an alternate approach to dark matter that assumes that highly relativistic protons trapped in the halo of the galaxies could account for the missing mass. We look at various energetics involved in such a scenario such as the energy required to produce such particles and the corresponding lifetimes. Also we look at the energy losses from synchrotron and inverse Compton scattering and their signatures. The Coulomb repulsive instability due to the excess charge around the galaxies is also calculated. The above results lead us to conclude that such a model for DM is unfeasible.

C. Sivaram; Kenath Arun; R. Nagaraja

2010-11-26T23:59:59.000Z

138

Black Hole Remnants and Dark Matter  

DOE Green Energy (OSTI)

We argue that, when the gravity effect is included, the generalized uncertainty principle (GUP) may prevent black holes from total evaporation in a similar way that the standard uncertainty principle prevents the hydrogen atom from total collapse. Specifically we invoke the GUP to obtain a modified Hawking temperature, which indicates that there should exist non-radiating remnants (BHR) of about Planck mass. BHRs are an attractive candidate for cold dark matter. We investigate an alternative cosmology in which primordial BHRs are the primary source of dark matter.

Chen, Pisin

2002-07-31T23:59:59.000Z

139

Dipole Moment Bounds on Dark Matter Annihilation  

E-Print Network (OSTI)

We consider constraints on simplified models in which scalar dark matter annihilates to light charged leptons through the exchange of charged mediators. We find that loop diagrams will contribute corrections to the magnetic and electric dipole moments of the light charged leptons, and experimental constraints on these corrections place significant bounds on the dark matter annihilation cross section. In particular, annihilation to electrons with an observable cross section would be ruled out, while annihilation to muons is only permitted if the dominant contributions arise from CP-violating interactions.

Keita Fukushima; Jason Kumar

2013-07-26T23:59:59.000Z

140

Might Dark Matter be Actually Black?  

DOE Green Energy (OSTI)

There have been proposals that primordial black hole remnants (BHRs) are the dark matter, but the idea is somewhat vague. We argue here first that the generalized uncertainty principle (GUP) may prevent black holes from evaporating completely, in a similar way that the standard uncertainty principle prevents the hydrogen atom from collapsing. Secondly we note that the hybrid inflation model provides a plausible mechanism for production of large numbers of small black holes. Combining these we suggest that the dark matter might be composed of Planck-size BHRs and discuss the possible constraints and signatures associated with this notion.

Chen, Pisin

2003-08-06T23:59:59.000Z

Note: This page contains sample records for the topic "dark matter searches" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


141

Generalized Uncertainty Principle and Dark Matter  

DOE Green Energy (OSTI)

There have been proposals that primordial black hole remnants (BHRs) are the dark matter, but the idea is somewhat vague. Recently we argued that the generalized uncertainty principle (GUP) may prevent black holes from evaporating completely, in a similar way that the standard uncertainty principle prevents the hydrogen atom from collapsing. We further noted that the hybrid inflation model provides a plausible mechanism for production of large numbers of small black holes. Combining these we suggested that the dark matter might be composed of Planck-size BHRs. In this paper we briefly review these arguments, and discuss the reheating temperature as a result of black hole evaporation.

Chen, P

2004-01-13T23:59:59.000Z

142

Dark Matter in the Light of COBE  

E-Print Network (OSTI)

The observations of all three COBE instruments are examined for the effects of dark matter. The anisotropy measured by the DMR, and especially the degree-scale ground- and balloon-based experiments, is only compatible with large-scale structure formation by gravity if the Universe is dominated by non-baryonic dark matter. The FIRAS instrument measures the total power radiated by cold dust, and thus places tight limits on the absorption of starlight by very cold gas and dust in the outer Milky Way. The DIRBE instrument measures the infrared background, and will place tight limits on the emission by low mass stars in the Galactic halo.

Edward L. Wright

1994-08-01T23:59:59.000Z

143

The possible nature of dark energy and dark matter Nathalie Olivi-Tran1,2  

E-Print Network (OSTI)

The possible nature of dark energy and dark matter Nathalie Olivi-Tran1,2 1 Laboratoire Charles of curvature have gravitational effects and deviate radiations. While we question dark energy, as another the nature of time. Keywords: dark matter; dark energy; nature of time 1 hal-00719998,version1-23Jul2012

Paris-Sud XI, Université de

144

A Field Theory Model for Dark Matter and Dark Energy in Interaction  

E-Print Network (OSTI)

We propose a field theory model for dark energy and dark matter in interaction. Comparing the classical solutions of the field equations with the observations of the CMB shift parameter, BAO, lookback time and Gold supernovae sample, we observe a possible interaction between dark sectors with energy decay from dark energy into dark matter. The observed interaction provides an alleviation to the coincidence problem.

Sandro Micheletti; Elcio Abdalla; Bin Wang

2009-02-02T23:59:59.000Z

145

Understanding the Fundamental Properties of Dark Matter and Dark Energy in Structure Formation and Cosmology  

Science Conference Proceedings (OSTI)

The program was concerned with developing and verifying the validity of observational methods for constraining the properties of dark matter and dark energy in the Universe.

Ellis, Richard S.

2012-09-30T23:59:59.000Z

146

Could Dark Matter Interactions be an Alternative to Dark Energy ?  

E-Print Network (OSTI)

We study the global dynamics of the universe within the framework of the Interacting Dark Matter (IDM) scenario. Assuming that the dark matter obeys the collisional Boltzmann equation, we can derive analytical solutions of the global density evolution, which can accommodate an accelerated expansion, equivalent to either the {\\em quintessence} or the standard $\\Lambda$ models, with the present time located after the inflection point. This is possible if there is a disequilibrium between the DM particle creation and annihilation processes with the former process dominating, which creates an effective source term with negative pressure. Comparing the predicted Hubble expansion of one of the IDM models (the simplest) with observational data we find that the effective annihilation term is quite small, as suggested by a variety of other recent experiments.

S. Basilakos; M. Plionis

2008-07-29T23:59:59.000Z

147

Determining Supersymmetric Parameters With Dark Matter Experiments  

Science Conference Proceedings (OSTI)

In this article, we explore the ability of direct and indirect dark matter experiments to not only detect neutralino dark matter, but to constrain and measure the parameters of supersymmetry. In particular, we explore the relationship between the phenomenological quantities relevant to dark matter experiments, such as the neutralino annihilation and elastic scattering cross sections, and the underlying characteristics of the supersymmetric model, such as the values of {mu} (and the composition of the lightest neutralino), m{sub A} and tan {beta}. We explore a broad range of supersymmetric models and then focus on a smaller set of benchmark models. We find that by combining astrophysical observations with collider measurements, {mu} can often be constrained far more tightly than it can be from LHC data alone. In models in the A-funnel region of parameter space, we find that dark matter experiments can potentially determine m{sub A} to roughly {+-}100 GeV, even when heavy neutral MSSM Higgs bosons (A, H{sub 1}) cannot be observed at the LHC. The information provided by astrophysical experiments is often highly complementary to the information most easily ascertained at colliders.

Hooper, Dan; /Fermilab; Taylor, Andrew M.; /Oxford U.

2006-07-01T23:59:59.000Z

148

ON THE LOCAL DARK MATTER DENSITY  

SciTech Connect

An analysis of the kinematics of 412 stars at 1-4 kpc from the Galactic midplane by Moni Bidin et al. has claimed to derive a local density of dark matter that is an order of magnitude below standard expectations. We show that this result is incorrect and that it arises from the assumption that the mean azimuthal velocity of the stellar tracers is independent of Galactocentric radius at all heights. We substitute the assumption, supported by data, that the circular speed is independent of radius in the midplane. We demonstrate that the assumption of constant mean azimuthal velocity is implausible by showing that it requires the circular velocity to drop more steeply than allowed by any plausible mass model, with or without dark matter, at large heights above the midplane. Using the approximation that the circular-velocity curve is flat in the midplane, we find that the data imply a local dark matter density of 0.008 {+-} 0.003 M{sub Sun} pc{sup -3} = 0.3 {+-} 0.1 GeV cm{sup -3}, fully consistent with standard estimates of this quantity. This is the most robust direct measurement of the local dark matter density to date.

Bovy, Jo; Tremaine, Scott [Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540 (United States)

2012-09-01T23:59:59.000Z

149

MoNDian Dark Matter, Entropic Gravity, and Infinite Statistics  

E-Print Network (OSTI)

We propose the concept of MoNDian dark matter which behaves like cold dark matter at cluster and cosmic scales but emulates modified Newtonian dynamics at the galactic scale. The connection between global physics and local galactic dynamics is implemented via entropic gravity. We also give an alternative formulation of MoNDian dark matter by using an effective gravitational Born-Infeld theory. In the latter approach, we show that the quanta of MoNDian dark matter obey infinite statistics.

Y. Jack Ng

2012-12-27T23:59:59.000Z

150

A New Dark Matter Model for Galaxies  

E-Print Network (OSTI)

In this paper a new theory of Dark Matter is proposed. Experimental analysis of several Galaxies show how the non-gravitational contribution to galactic Velocity Rotation Curves can be interpreted as that due to the Cosmological Constant ?. The experimentally determined values for ? are found to be consistent with those expected from Cosmological Constraints. The Cosmological Constant is interpreted as leading to a constant energy density which in turn can be used to partly address the energy deficit problem (Dark Energy) of the Universe. The work presented here supports the proposal for an accelerating universe and that we live in a quasi de-Sitter universe.

George Kraniotis; Steven Whitehouse

2000-01-01T23:59:59.000Z

151

A Quantum Approach to Dark Matter  

E-Print Network (OSTI)

This work develops and explores a quantum-based theory which enables the nature and origin of cold dark matter (CDM) to be understood without need to introduce exotic particles. The quantum approach predicts the existence of certain macroscopic quantum structures that are WIMP-like even when occupied by traditional baryonic particles. These structures function as dark matter candidates for CDM theory on large scales where it has been most successful, and retain the potential to yield observationally compliant predictions on galactic cluster and sub-cluster scales. Relatively pure, high angular momentum, eigenstate solutions obtained from Schrodinger's equation in weak gravity form the structural basis. They have no classical analogue, and properties radically different from those of traditional localised matter (whose eigenstate spectra contain negligible quantities of such states). Salient features include radiative lifetimes that can exceed the age of the universe, energies and 'sizes' consistent with galactic halos, and negligible interaction rates with radiation and macroscopic galactic objects. This facilitates the formation of sparsely populated macroscopic quantum structures that are invisible and stable. Viable structure formation scenarios are based on the seed potential wells of primordial black holes formed at the e+/e- phase transition. The structures can potentially produce suitable internal density distributions and have capacity to accommodate the required amount of halo dark matter. The formation scenarios show that it is possible to incorporate structures into universal evolutionary scenarios without significantly compromising the results of WMAP or the measurements of elemental BBN ratios.

A. D. Ernest

2004-06-06T23:59:59.000Z

152

The physics and identity of dark matter  

E-Print Network (OSTI)

This paper follows "The physics and identity of Dark Energy", which is the acceleration energy of old photons. The present paper considers everything else in the decay of our universe; it is an ensemble called "old protons, etc."; the ensemble will be listed. The accelerated expansion of our universe brings the decay debris into the inter-universal medium (IUM) of the multiverse, where it is conserved during long times. Debris clouds eventually accrete from the IUM and grow into proto-universes. The protons, etc. are involved as much as are the photons; they are the receivers of the kinetic energy of photon acceleration. Dark matter is therefore the matter of "old protons,etc." mentioned before.

Tom Gehrels

2010-12-30T23:59:59.000Z

153

Have Atmospheric Cerenkov Telescopes Observed Dark Matter?  

E-Print Network (OSTI)

Two ground-based experiments have recently independently detected TeV $\\gamma$-rays from the direction of the Galactic center. The observations made by the VERITAS and CANGAROO collaborations are unexpected, although not impossible to interpret in terms of astrophysical sources. Here we examine in detail whether the observed $\\gamma$-rays may arise from the more exotic alternative of annihilations of dark matter particles clustered in the center of the Galaxy.

Dan Hooper; Ignacio de la Calle Perez; Joseph Silk; Francesc Ferrer; Subir Sarkar

2004-04-09T23:59:59.000Z

154

Death of Stellar Baryonic Dark Matter Candidates  

E-Print Network (OSTI)

The nature of the dark matter in the Universe is one of the outstanding questions in astrophysics. In this talk, I address possible stellar baryonic contributions to the 50-90% of our Galaxy that is made of unknown dark matter. First I show that faint stars and brown dwarfs constitute only a few percent of the mass of the Galaxy. Next, I show that stellar remnants, including white dwarfs and neutron stars, are also insufficient in abundance to explain all the dark matter of the Galaxy. High energy gamma-rays observed in HEGRA data place the most robust constraints, $\\Omega_{WD} < 3 \\times 10^{-3} h^{-1}$, where $h$ is the Hubble constant in units of 100 km s$^{-1}$ Mpc$^{-1}$. Overproduction of chemical abundances (carbon, nitrogen, and helium) provide the most stringent constraints, $\\Omega_{WD} < 2 \\times 10^{-4} h^{-1}$. Comparison with recent updates of microlensing data are also made. According to the gamma-ray limit, all Massive Compact Halo Objects seen by the experiments (Machos) can be white dwarfs if one takes the extreme numbers; however, from chemical overproduction limits, NOT all Machos can be white dwarfs. Comments on recent observations of the infrared background and of white dwarfs are also made. In conclusion, a nonbaryonic component in the Halo seems to be required.

Katherine Freese; Brian Fields; David Graff

2000-07-28T23:59:59.000Z

155

High Energy Positrons From Annihilating Dark Matter  

E-Print Network (OSTI)

Recent preliminary results from the PAMELA experiment indicate the presence of an excess of cosmic ray positrons above 10 GeV. In this letter, we consider possibility that this signal is the result of dark matter annihilations taking place in the halo of the Milky Way. Rather than focusing on a specific particle physics model, we take a phenomenological approach and consider a variety of masses and two-body annihilation modes, including W+W-, ZZ, b bbar, tau+ tau-, mu+ mu-, and e+e. We also consider a range of diffusion parameters consistent with current cosmic ray data. We find that a significant upturn in the positron fraction above 10 GeV is compatible with a wide range of dark matter annihilation modes, although very large annihilation cross sections and/or boost factors arising from inhomogeneities in the local dark matter distribution are required to produce the observed intensity of the signal. We comment on constraints from gamma rays, synchrotron emission, and cosmic ray antiproton measurements.

Ilias Cholis; Lisa Goodenough; Dan Hooper; Melanie Simet; Neal Weiner

2008-09-10T23:59:59.000Z

156

DOE Science Showcase - Dark Matter and Dark Energy | OSTI, US Dept of  

Office of Scientific and Technical Information (OSTI)

Dark Matter and Dark Energy Dark Matter and Dark Energy The nature of dark energy or invisible energy is one of the universe's most compelling mysteries and its resolution is likely to completely change our understanding of matter, space, and time. For more information, see In the OSTI Collections: Dark Matter and Dark Energy, by Dr. William Watson, Physicist, OSTI staff. Gravitational lensing, or the warping of light around massive objects is one sign of dark energy Image Credit: NASA/Andy Fruchter/ERO team Dark energy research information: Temperature and Density Conditions for Nucleogenesis by Fusion Processes in Stars, William Fowler, DOE R&D Accomplishments Saul Perlmutter, Distant Supernovae, Dark Energy, and the Accelerating Expansion of the Universe, DOE R&D Accomplishments

157

Mapping and Embedding of Two Metrics Associated with Dark Matter, Dark Energy, and Ordinary Matter  

E-Print Network (OSTI)

In this paper we build a mapping between two different metrics and embed them in a flat manifold. One of the metrics represents the ordinary matter, and the other describes the dark matter, the dark energy, and the particle-antiparticle asymmetry. The latter was obtained in a recent paper. For the mapping and embedding, we use two new formalisms developed and presented in two previous papers, Mapping Among Manifolds and, Conformal Form of Pseudo-Riemannian Metrics by Normal Coordinate Transformations, which was a generalization of the Cartan's approach of Riemannian normal coordinates.

de Siqueira, A C V V

2010-01-01T23:59:59.000Z

158

Mapping and Embedding of Two Metrics Associated with Dark Matter, Dark Energy, and Ordinary Matter  

E-Print Network (OSTI)

In this paper we build a mapping between two different metrics and embed them in a flat manifold. One of the metrics represents the ordinary matter, and the other describes the dark matter, the dark energy, and the particle-antiparticle asymmetry. The latter was obtained in a recent paper. For the mapping and embedding, we use two new formalisms developed and presented in two previous papers, Mapping Among Manifolds and, Conformal Form of Pseudo-Riemannian Metrics by Normal Coordinate Transformations, which was a generalization of the Cartan's approach of Riemannian normal coordinates.

A. C. V. V. de Siqueira

2010-10-29T23:59:59.000Z

159

Dark matter and EWSB naturalness in unified SUSY models  

SciTech Connect

The relationship between the degree of fine-tuning in Electroweak Symmetry Breaking (EWSB) and the discoverability of dark matter in current and next generation direct detection experiments is investigated in the context of two unified Supersymmetry scenarios: the Constrained Minimal Supersymmetric Standard Model (CMSSM) and models with Non-Universal Higgs Masses (NUHM). Attention is drawn to the mechanism(s) by which the relic abundance of neutralino dark matter is suppressed to cosmologically viable values. After a summary of Amsel, Freese, and Sandick (2011), results are updated to reflect current constraints, including the discovery of a new particle consistent with a Standard Model-like Higgs boson. We find that a Higgs mass of {approx} 125 GeV excludes the least fine-tuned CMSSM points in our parameter space and that remaining viable models may be difficult to probe with next generation direct dark matter searches. Relatively low fine-tuning and good direct detection prospects are still possible in NUHM scenarios.

Sandick, Pearl [University of Utah, Dept. of Physics, Salt Lake City, UT 84112 (United States)

2013-05-23T23:59:59.000Z

160

Snowmass CF1 Summary: WIMP Dark Matter Direct Detection  

E-Print Network (OSTI)

As part of the Snowmass process, the Cosmic Frontier WIMP Direct Detection subgroup (CF1) has drawn on input from the Cosmic Frontier and the broader Particle Physics community to produce this document. The charge to CF1 was (a) to summarize the current status and projected sensitivity of WIMP direct detection experiments worldwide, (b) motivate WIMP dark matter searches over a broad parameter space by examining a spectrum of WIMP models, (c) establish a community consensus on the type of experimental program required to explore that parameter space, and (d) identify the common infrastructure required to practically meet those goals.

P. Cushman; C. Galbiati; D. N. McKinsey; H. Robertson; T. M. P. Tait; D. Bauer; A. Borgland; B. Cabrera; F. Calaprice; J. Cooley; T. Empl; R. Essig; E. Figueroa-Feliciano; R. Gaitskell; S. Golwala; J. Hall; R. Hill; A. Hime; E. Hoppe; L. Hsu; E. Hungerford; R. Jacobsen; M. Kelsey; R. F. Lang; W. H. Lippincott; B. Loer; S. Luitz; V. Mandic; J. Mardon; J. Maricic; R. Maruyama; R. Mahapatra; H. Nelson; J. Orrell; K. Palladino; E. Pantic; R. Partridge; A. Ryd; T. Saab; B. Sadoulet; R. Schnee; W. Shepherd; A. Sonnenschein; P. Sorensen; M. Szydagis; T. Volansky; M. Witherell; D. Wright; K. Zurek

2013-10-30T23:59:59.000Z

Note: This page contains sample records for the topic "dark matter searches" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


161

Inhomogeneous models of interacting dark matter and dark energy  

E-Print Network (OSTI)

We derive and analyze a class of spherically symmetric cosmological models whose source is an interactive mixture of inhomogeneous cold dark matter (DM) and a generic homogeneous dark energy (DE) fluid. If the DE fluid corresponds to a quintessense scalar field, the interaction term can be associated with a well motivated non--minimal coupling to the DM component. By constructing a suitable volume average of the DM component we obtain a Friedman evolution equation relating this average density with an average Hubble scalar, with the DE component playing the role of a repulsive and time-dependent $\\Lambda$ term. Once we select an ``equation of state'' linking the energy density ($\\mu$) and pressure ($p$) of the DE fluid, as well as a free function governing the radial dependence, the models become fully determinate and can be applied to known specific DE sources, such as quintessense scalar fields or tachyonic fluids. Considering the simple equation of state $p= (\\gamma-1) \\mu$ with $0\\leq\\gamma description of a local DM overdensity evolving in a suitable cosmic background that accurately fits current observational data. While a DE dominated scenario emerges in the asymptotic future, with total $\\Omega$ and $q$ tending respectively to 1 and -1/2 for all cosmic observers, the effects of inhomogeneity and anisotropy yield different local behavior and evolution rates for these parameters in the local overdense region. We suggest that the models presented can be directly applied to explore the effects of various DE formalisms on local DM cosmological inhomogeneities.

Roberto A Sussman; Israel Quiros; Osmel Martin Gonzalez

2005-03-29T23:59:59.000Z

162

Inhomogeneous models of interacting dark matter and dark energy  

E-Print Network (OSTI)

We derive and analyze a class of spherically symmetric cosmological models whose source is an interactive mixture of inhomogeneous cold dark matter (DM) and a generic homogeneous dark energy (DE) fluid. If the DE fluid corresponds to a quintessense scalar field, the interaction term can be associated with a well motivated non--minimal coupling to the DM component. By constructing a suitable volume average of the DM component we obtain a Friedman evolution equation relating this average density with an average Hubble scalar, with the DE component playing the role of a repulsive and time-dependent $\\Lambda$ term. Once we select an ``equation of state'' linking the energy density ($\\mu$) and pressure ($p$) of the DE fluid, as well as a free function governing the radial dependence, the models become fully determinate and can be applied to known specific DE sources, such as quintessense scalar fields or tachyonic fluids. Considering the simple equation of state $p= (\\gamma-1) \\mu$ with $0\\leq\\gamma <2/3$, we s...

Sussman, R A; Gonzalez, O M; Sussman, Roberto A; Quiros, Israel; Gonzalez, Osmel Martin

2005-01-01T23:59:59.000Z

163

Tommaso Treu, UC Santa Barbara What is the nature of dark energy and dark matter?  

E-Print Network (OSTI)

Tommaso Treu, UC Santa Barbara What is the nature of dark energy and dark matter? I will describe on the equation of state of dark energy and flatness comparable to those obtained with the best probes. The second the presence of dark subhalos independent of their stellar content. This tests a fundamental prediction

Glashausser, Charles

164

Measuring Dark Matter Distribution in Directional Direct Detection  

E-Print Network (OSTI)

Direct detection of dark matter with directional sensitivity offers not only measurement of both recoil energy and direction of dark matter, but also a way to understand dark matter distribution in the Galaxy. Maxwell distribution is usually supposed as the distribution near the Earth, however, deviation from that, caused by tidal streams in the Galaxy, has been suggested. We explore the possibility of distinguishing the distribution by direct detection using nuclear emulsions.

Keiko I. Nagao

2013-12-11T23:59:59.000Z

165

Dark Energy and Search for the Generalized Second Law  

E-Print Network (OSTI)

The discovery of accelerated Hubble expansion in the SNIa data and the observed power spectrum of the microwave background radiation provide an ample support for Dark energy and Dark matter. Except for the so far well-known facts that cold dark matter (or simply dark matter) is pressureless, and dark energy has a negative pressure, the nature of these two still remains a complete mystery. The mystery facilitates different consideration. In one hand, dark matter and dark energy are assumed as distinct entities, and other interpretation is that both are different manifestation of a common structure, often referred as quartessence. Chaplygin gas, a perfect fluid also favours the second interpretation. Here, we consider modified chaplygin gas as dark energy candidate. Taking into account the existence of the observer's event horizon in accelerated universe, we find the condition where the generalized second law of gravitational thermodynamics is valid and the positivity of the temperature of the phantom fluid remains intact.

Balendra Kr. Dev Choudhury; Julie Saikia

2009-06-03T23:59:59.000Z

166

Warped Unification, Proton Stability and Dark Matter  

E-Print Network (OSTI)

Many extensions of the Standard Model have to face the problem of new unsuppressed baryon-number violating interactions. In supersymmetry, the simplest way to solve this problem is to assume R-parity conservation. As a result, the lightest supersymmetric particle becomes stable and a well-motivated dark matter candidate. In this paper, we show that solving the problem of baryon number violation in non supersymmetric grand unified theories (GUT's) in warped higher-dimensional spacetime can lead to a stable Kaluza-Klein particle. This exotic particle has gauge quantum numbers of a right-handed neutrino, but carries fractional baryon-number and is related to the top quark within the higher-dimensional GUT. A combination of baryon-number and SU(3) color ensures its stability. Its relic density can easily be of the right value for masses in the 10 GeV--few TeV range. An exciting aspect of these models is that the entire parameter space will be tested at near future dark matter direct detection experiments. Other exotic GUT partners of the top quark are also light and can be produced at high energy colliders with distinctive signatures.

Kaustubh Agashe; Geraldine Servant

2004-03-15T23:59:59.000Z

167

The bias field of dark matter haloes  

E-Print Network (OSTI)

This paper presents a stochastic approach to the clustering evolution of dark matter haloes in the Universe. Haloes, identified by a Press-Schechter-type algorithm in Lagrangian space, are described in terms of `counting fields', acting as non-linear operators on the underlying Gaussian density fluctuations. By ensemble averaging these counting fields, the standard Press-Schechter mass function as well as analytic expressions for the halo correlation function and corresponding bias factors of linear theory are obtained, thereby extending the recent results by Mo and White. The non-linear evolution of our halo population is then followed by solving the continuity equation, under the sole hypothesis that haloes move by the action of gravity. This leads to an exact and general formula for the bias field of dark matter haloes, defined as the local ratio between their number density contrast and the mass density fluctuation. Besides being a function of position and `observation' redshift, this random field depends upon the mass and formation epoch of the objects and is both non-linear and non-local. The latter features are expected to leave a detectable imprint on the spatial clustering of galaxies, as described, for instance, by statistics like bispectrum and skewness. Our algorithm may have several interesting applications, among which the possibility of generating mock halo catalogues from low-resolution N-body simulations.

P. Catelan; F. Lucchin; S. Matarrese; C. Porciani

1997-08-07T23:59:59.000Z

168

Gas and Dark Matter Spherical Dynamics  

E-Print Network (OSTI)

We investigate the formation of spherical cosmological structures following both dark matter and gas components. We focus on the dynamical aspect of the collapse assuming an adiabatic, $\\gamma = 5/3$, fully ionized primordial plasma. We use for that purpose a fully Lagrangian hydrodynamical code designed to describe highly compressible flows in spherical geometry. We investigate also a "fluid approach" to describe the mean physical quantities of the dark matter flow. We test its validity for a wide range of initial density contrast. We show that an homogeneous isentropic core forms in the gas distribution, surrounded by a self-similar hydrostatic halo, with much higher entropy generated by shock dissipation. We derive analytical expressions for the size, density and temperature of the core, as well as for the surrounding halo. We show that, unless very efficient heating processes occur in the intergalactic medium, we are unable to reproduce within adiabatic models the typical core sizes in X-ray clusters. We also show that, for dynamical reasons only, the gas distribution is naturally antibiased relative to the total mass distribution, without invoking any reheating processes. This could explain why the gas fraction increases with radius in very large X-ray clusters. As a preparation for the next study devoted to the thermodynamical aspect of the collapse, we investigate the initial entropy level required to solve the core problem in X-ray clusters.

Jean-Pierre CHIEZE; Romain Teyssier; Jean-Michel Alimi

1997-04-03T23:59:59.000Z

169

Hierarchical Phase Space Structure of Dark Matter Haloes: Tidal debris, Caustics, and Dark Matter annihilation  

E-Print Network (OSTI)

Most of the mass content of dark matter haloes is expected to be in the form of tidal debris. The density of debris is not constant, but rather can grow due to formation of caustics at the apocenters and pericenters of the orbit, or decay as a result of phase mixing. In the phase space, the debris assemble in a hierarchy which is truncated by the primordial temperature of dark matter. Understanding this phase structure can be of significant importance for the interpretation of many astrophysical observations and in particular dark matter detection experiments. With this purpose in mind, we develop a general theoretical framework to describe the hierarchical structure of the phase space of cold dark matter haloes. We do not make any assumption of spherical symmetry and/or smooth and continuous accretion. Instead, working with correlation functions in the action-angle space, we can fully account for the hierarchical structure (predicting a two-point correlation function ~ (\\Delta J)^{-1.6} in the action space), as well as the primordial discreteness of the phase space. As an application, we estimate the boost to the dark matter annihilation signal due to the structure of the phase space within virial radius: the boost due to the hierarchical tidal debris is of order unity, whereas the primordial discreteness of the phase structure can boost the total annihilation signal by up to an order of magnitude. The latter is dominated by the regions beyond 20% of the virial radius, and is largest for the recently formed haloes with the least degree of phase mixing.

Niayesh Afshordi; Roya Mohayaee; Edmund Bertschinger

2008-11-10T23:59:59.000Z

170

A New Generalized Chaplygin Gas as a Scheme for Unification of Dark Energy and Dark Matter  

E-Print Network (OSTI)

We propose a new model for the description of unification of dark energy and dark matter, dubbed new generalized Chaplygin gas (NGCG) model. We study the cosmological scenario arising from the dynamics of this new generalized Chaplygin gas. The equation of state of the system is given by p = ?A(a)/? ?, where a is the scale factor and 0 dark matter decays to dark energy. From this scenario, the origin of the ”intermediate regime” (p = ?wX??) is clarified and the production mechanism of the acoustics is illustrated. 1 Recently, a kind of description for unification of dark energy and dark matter, the so called generalized Chaplygin gas(GCG), was proposed for understanding the observed accelerated expansion of the universe [1,2]. The scenario of this model is that dark energy and dark matter are different aspects of a single exotic substance permeated in the whole

Xin Zhang

2004-01-01T23:59:59.000Z

171

OBSERVATIONAL EVIDENCE FOR DARK MATTER INTERACTING THROUGH A YUKAWA POTENTIAL  

SciTech Connect

Recent observations in galaxies and clusters indicate that dark matter density profiles exhibit core-like structures which contradict the numerical simulation results of collisionless cold dark matter (CDM). On the other hand, it has been shown that CDM particles interacting through a Yukawa potential could naturally explain the cores in dwarf galaxies. In this Letter, I use the Yukawa potential interacting dark matter model to derive two simple scaling relations on the galactic and cluster scales, respectively, which give excellent agreements with observations. Also, in our model, the masses of the force carrier and dark matter particle can be constrained by the observational data.

Chan, M. H., E-mail: mhchan@phy.cuhk.edu.hk [Department of Physics and Institute of Theoretical Physics, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong (Hong Kong)

2013-05-20T23:59:59.000Z

172

The Higgs portal and an unified model for dark energy and dark matter  

E-Print Network (OSTI)

We examine a scenario where the Higgs boson is coupled to an additional singlet scalar field which we identify with a quintessence field. We show that this results in an unified picture of dark matter and dark energy, where dark energy is the zero-mode classical field rolling the usual quintessence potential and the dark matter candidate is the quantum excitation (particle) of the field, which is produced in the universe due to its coupling to the Higgs boson.

O. Bertolami; R. Rosenfeld

2007-08-13T23:59:59.000Z

173

Search for Low-Mass Dark-Sector Higgs Bosons  

E-Print Network (OSTI)

Recent astrophysical and terrestrial experiments have motivated the proposal of a dark sector with GeV-scale gauge boson force carriers and new Higgs bosons. We present a search for a dark Higgs boson using 516??fb[superscript ...

Cowan, Ray Franklin

174

A Laboratory Search for Dark Energy  

E-Print Network (OSTI)

The discovery of the accelerating universe indicates strongly the presence of a scalar field which is not only expected to solve today's version of the cosmological constant problem, or the fine-tuning and the coincidence problems, but also provides a way to understand dark energy. It has also been shown that Jordan's scalar-tensor theory is now going to be re-discovered in the new lights. In this letter we suggest a way to search for the extremely light scalar field by means of a laboratory experiment on the low-energy photon-photon interactions with the quasi-parallel incident beams.

Yasunori Fujii; Kensuke Homma

2009-12-28T23:59:59.000Z

175

Gravitational collapse due to dark matter and dark energy in the brane world scenario  

E-Print Network (OSTI)

Gravitational collapse of FRW brane world embedded in a conformaly flat bulk is considered for matter cloud consists of dark matter and dark energy with equation of state $p=\\epsilon \\rho$ $(\\epsilondark matter and dark energy is being considered first separately and then a combination of them both with and without interaction. In some cases the collapse leads to black hole in some other cases naked singularity appears.

Soma Nath; Subenoy Chakraborty; Ujjal Debnath

2005-12-21T23:59:59.000Z

176

Dark Matter and Dark Energy as Effects of Quantum Gravity  

E-Print Network (OSTI)

I present a theory of quantum gravity based on the principle of gravitational energy fluctuations. Gravitational energy fluctuations -- gravitons -- are responsible for elastic scattering of subatomic particles. Such scattering corresponds to complimentary force -- graviton scattering force -- arising in gravitational interaction in addition to Newtonian gravity. The strength of the graviton scattering force is proportional to the graviton scattering probability. Unlike Newtonian gravity the graviton scattering force follows the 1/r law and dominates the former on cosmological scale in the limit of low orbital accelerations. Similarly to Modified Newtonian Dynamics the quantum gravity accounts for variations in observed M/L ratios of diverse stellar systems ranging from dwarf spheroid galaxies to X-ray galaxy clusters without requiring an invisible matter (which is still required by MOND in X-Ray cluster cores). Unlike MOND the presented theory neither violates cornerstone Newton Laws nor suffers from the ambiguity of acceleration frames while enjoying vast experimental evidence usually cited in favor of MOND. To ascertain the validity of the presented theory I have examined the predictions of quantum gravity for dwarf spheroid, ordinary and giant elliptic galaxies, and X-ray clusters. In all cases quantum gravity yields M/L ratios and scaling relations consistent with observations. Quantum gravity accounts for the tilt of the Fundamental Plane of elliptical galaxies erasing the differences in M/L vs. luminosity relations for faint and bright ellipticals, which cannot be easily explained by CDM model. Lastly, by analyzing the behavior of the gravitational energy fluctuations in the limit of high matter density expected in the early Universe I show that primordial inflation and dark energy (i.e. non-zero cosmological constant) arise as natural effects of quantum gravity in the expanding Universe.

Max I. Fomitchev

2010-09-07T23:59:59.000Z

177

Dark Matter and a Definite Non-Definite | Department of Energy  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

Dark Matter and a Definite Non-Definite Dark Matter and a Definite Non-Definite Dark Matter and a Definite Non-Definite April 17, 2013 - 4:22pm Addthis The Alpha Magnetic Spectrometer experiment is a particle detector which was lofted to the International Space Station onboard the Space Shuttle Endeavour about two years ago. | Image courtesy of NASA. The Alpha Magnetic Spectrometer experiment is a particle detector which was lofted to the International Space Station onboard the Space Shuttle Endeavour about two years ago. | Image courtesy of NASA. Charles Rousseaux Charles Rousseaux Senior Writer, Office of Science LEARN MORE Several national labs are involved with the search for dark matter including Berkeley Lab, Fermilab and SLAC National Accelerator Laboratory. When is a definite non-definite worth noting? Perhaps when there's

178

Longevity Problem of Sterile Neutrino Dark Matter  

E-Print Network (OSTI)

Sterile neutrino dark matter of mass O(1-10) keV decays into an active neutrino and an X-ray photon, and the non-observation of the corresponding X-ray line requires the sterile neutrino to be more long-lived than estimated based on the seesaw formula : the longevity problem. We show that, if one or more of the B-L Higgs fields are charged under a flavor symmetry (or discrete R symmetry), the split mass spectrum for the right-handed neutrinos as well as the required longevity is naturally realized. We provide several examples in which the predicted the X-ray flux is just below the current bound.

Hiroyuki Ishida; Kwang Sik Jeong; Fuminobu Takahashi

2013-09-12T23:59:59.000Z

179

Mini Little Higgs and Dark Matter  

E-Print Network (OSTI)

We construct a little Higgs model with the most minimal extension of the standard model gauge group by an extra U(1) gauge symmetry. For specific charge assignments of scalars, an approximate U(3) global symmetry appears in the cutoff-squared scalar mass terms generated from gauge bosons at one-loop level. Hence, the Higgs boson, identified as a pseudo-Goldstone boson of the broken global symmetry, has its mass radiatively protected up to scales of 5-10 TeV. In this model, a Z2 symmetry, ensuring the two U(1) gauge groups to be identical, also makes the extra massive neutral gauge boson stable and a viable dark matter candidate with a promising prospect of direct detection.

Yang Bai

2008-01-10T23:59:59.000Z

180

"Jordan's Scalar Stars" and Dark Matter  

E-Print Network (OSTI)

Here we are starting the study of the field equations of relativistic scalar tensor theories in the spherically symmetric gravitational field. In the present article we shall consider as an example only the simplest Jordan-Brans-Dicke (JBD) one. To illustrate the property of the spherically symmetric JBD configuration we exhibit a new representation of the well-known four dimensional solutions. In this model, a suitable segment of Brans solution is chosen for the interior of the object while the outer region consists of a Schwarzschild vacuum. We have constructed "Jordan's scalar stars" model consisting of three parts: a homogeneous inner core with linear equation of state; an envelope of Brans spacetime matching the core and the exterior Schwarzschild spacetime. We have also showed that this toy model can explain the intergalactic effects without the dark matter hypothesis.

S. M. Kozyrev

2008-08-25T23:59:59.000Z

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181

Indistinguishability of Warm Dark Matter, Modified Gravity, and Coupled Cold Dark Matter  

E-Print Network (OSTI)

The current accelerated expansion of our universe could be due to an unknown energy component with negative pressure (dark energy) or a modification to general relativity (modified gravity). On the other hand, recently warm dark matter (WDM) remarkably rose as an alternative of cold dark energy (CDM). Obviously, it is of interest to distinguish these different types of models. In fact, many attempts have been made in the literature. However, in this work we show that WDM, modified gravity and coupled CDM form a trinity, namely, they are indistinguishable by using the cosmological observations of both cosmic expansion history and growth history. Therefore, to break the degeneracy, the other complementary probes beyond the ones of cosmic expansion history and growth history are required.

Wei, Hao; Chen, Zu-Cheng; Yan, Xiao-Peng

2013-01-01T23:59:59.000Z

182

Dark Matter Stabilization Symmetries from Spontaneous Symmetry Breaking  

E-Print Network (OSTI)

We present a class of models in which the dark matter stabilization symmetry is generated by spontaneous symmetry breaking. These models naturally correlate the dark and electroweak symmetry breaking scales. The result is a generic mechanism linking the annihilation cross section for thermally populated dark matter with the weak scale. The thermal relic abundance, sensitivity to major precision electroweak observables and additional LHC signatures are also presented.

Walker, Devin G E

2009-01-01T23:59:59.000Z

183

Dark Matter Stabilization Symmetries from Spontaneous Symmetry Breaking  

E-Print Network (OSTI)

We present a class of models in which the dark matter stabilization symmetry is generated by spontaneous symmetry breaking. These models naturally correlate the dark and electroweak symmetry breaking scales. The result is a generic mechanism linking the annihilation cross section for thermally populated dark matter with the weak scale. The thermal relic abundance, sensitivity to major precision electroweak observables and additional LHC signatures are also presented.

Devin G. E. Walker

2009-07-20T23:59:59.000Z

184

Galactic structure explained with dissipative mirror dark matter  

E-Print Network (OSTI)

Dissipative dark matter, such as mirror dark matter and related hidden sector dark matter candidates, requires an energy source to stabilize dark matter halos in spiral galaxies. It has been proposed previously that supernovae could be the source of this energy. Recently, it has been argued that this mechanism might explain two galactic scaling relations inferred from observations of spiral galaxies. One of which is that $\\rho_0 r_0$ is roughly constant, and another relates the galactic luminosity to $r_0$. [$\\rho_0$ is the dark matter central density and $r_0$ is the core radius.] Here we derive equations for the heating of the halo via supernova energy, and the cooling of the halo via thermal bremsstrahlung. These equations are numerically solved to obtain constraints on the $\\rho_0, \\ r_0$ parameters appropriate for spiral galaxies. These constraints are in remarkable agreement with the aforementioned scaling relations.

R. Foot

2013-04-17T23:59:59.000Z

185

A Terrestrial Search for Dark Contents of the Vacuum, Such as Dark Energy, Using Atom Interferometry  

SciTech Connect

We describe the theory and first experimental work on our concept for searching on earth for the presence of dark contents of the vacuum (DCV) using atom interferometry. Specifically, we have in mind any DCV that has not yet been detected on a laboratory scale, but which might manifest itself as dark energy on the cosmological scale. The experimental method uses two atom interferometers to cancel the effect of earth's gravity and diverse noise sources. It depends upon two assumptions: first, that the DCV possesses some space inhomogeneity in density, and second that it exerts a sufficiently strong nongravitational force on matter. The motion of the apparatus through the DCV should then lead to an irregular variation in the detected matter-wave phase shift. We discuss the nature of this signal and note the problem of distinguishing it from instrumental noise. We also discuss the relation of our experiment to what might be learned by studying the noise in gravitational wave detectors such as LIGO. The paper concludes with a projection that a future search of this nature might be carried out using an atom interferometer in an orbiting satellite. The laboratory apparatus is now being constructed.

Adler, Ronald J.; /Stanford U., HEPL /San Francisco State U.; Muller, Holger; /UC, Berkeley; Perl, Martin L.; /KIPAC, Menlo Park /SLAC

2012-06-11T23:59:59.000Z

186

Discovery of underground argon with low level of radioactive 39Ar and possible applications to WIMP dark matter detectors  

E-Print Network (OSTI)

We report on the first measurement of 39Ar in argon from underground natural gas reservoirs. The gas stored in the US National Helium Reserve was found to contain a low level of 39Ar. The ratio of 39Ar to stable argon was found to be important backgrounds in argon detectors for WIMP dark matter searches. The findings reported demonstrate the possibility of constructing large multi-ton argon detectors with low radioactivity suitable for WIMP dark matter searches.

Galbiati, C

2007-01-01T23:59:59.000Z

187

Discovery of underground argon with low level of radioactive 39Ar and possible applications to WIMP dark matter detectors  

E-Print Network (OSTI)

We report on the first measurement of 39Ar in argon from underground natural gas reservoirs. The gas stored in the US National Helium Reserve was found to contain a low level of 39Ar. The ratio of 39Ar to stable argon was found to be important backgrounds in argon detectors for WIMP dark matter searches. The findings reported demonstrate the possibility of constructing large multi-ton argon detectors with low radioactivity suitable for WIMP dark matter searches.

C. Galbiati; R. Purtschert

2007-12-03T23:59:59.000Z

188

arXiv:0706.2986v1[astro-ph]20Jun2007 DARK MATTER AND DARK ENERGY  

E-Print Network (OSTI)

arXiv:0706.2986v1[astro-ph]20Jun2007 DARK MATTER AND DARK ENERGY MARC KAMIONKOWSKI California, and/or the introduction of some negative-pressure "dark energy," again, the nature of which remains Press. kamion@tapir.caltech.edu 1 #12;Dark Matter and Dark Energy 2 eries may help us understand the new

Steidel, Chuck

189

Holographic dark energy interacting with dark matter in a Closed Universe  

E-Print Network (OSTI)

A cosmological model of an holographic dark energy interacting with dark matter throughout a decaying term of the form $Q=3(\\lambda_1\\rho_{DE} + \\lambda_2\\rho_m) H$ is investigated. General constraint on the parameters of the model are found when accelerated expansion is imposed and we found a phantom scenarios, without any reference to a specific equation of state for the dark energy. The behavior of equation of stated for dark energy is also discussed.

Norman Cruz; Samuel Lepe; Francisco Pena; Joel Saavedra

2008-07-24T23:59:59.000Z

190

Low Energy INTEGRAL Positrons from eXciting Dark Matter  

E-Print Network (OSTI)

The origin of the e^+e^- 511 keV line observed by INTEGRAL remains unclear. The rate and morphology of the signal have prompted questions as to whether dark matter could play a role. We explore the case of dark matter upscattering in the framework of eXciting Dark Matter (XDM), where WIMPs \\chi, interacting through a new dark force, scatter into excited states \\chi*, which subsequently emit e^+e^- pairs when they de-excite. We numerically compute the cross sections for two Yukawa-coupled DM particles upscattering into excited states, specifically considering variations motivated by recent N-body simulations with additional baryonic physics. We find that that l>0 components of the partial-wave decomposition are often significant contributions to the total cross section and that for reasonable ranges of parameters dark matter can produce the ~10^43 e^+/s observed by INTEGRAL.

Rob Morris; Neal Weiner

2011-09-17T23:59:59.000Z

191

DARK MATTER POWERED STARS: CONSTRAINTS FROM THE EXTRAGALACTIC BACKGROUND LIGHT  

SciTech Connect

The existence of predominantly cold non-baryonic dark matter is unambiguously demonstrated by several observations (e.g., structure formation, big bang nucleosynthesis, gravitational lensing, and rotational curves of spiral galaxies). A candidate well motivated by particle physics is a weakly interacting massive particle (WIMP). Self-annihilating WIMPs would affect the stellar evolution especially in the early universe. Stars powered by self-annihilating WIMP dark matter should possess different properties compared with standard stars. While a direct detection of such dark matter powered stars seems very challenging, their cumulative emission might leave an imprint in the diffuse metagalactic radiation fields, in particular in the mid-infrared part of the electromagnetic spectrum. In this work, the possible contributions of dark matter powered stars (dark stars, DSs) to the extragalactic background light (EBL) are calculated. It is shown that existing data and limits of the EBL intensity can already be used to rule out some DS parameter sets.

Maurer, A.; Raue, M.; Kneiske, T.; Horns, D. [Institut fuer Experimentalphysik, Universitaet Hamburg, Luruper Chaussee 149, D-22761 Hamburg (Germany); Elsaesser, D. [Institut fuer Theoretische Physik und Astrophysik, Am Hubland, D-97074 Wuerzburg (Germany); Hauschildt, P. H., E-mail: andreas.maurer@physik.uni-hamburg.de [Hamburger Sternwarte, Gojenbergsweg 112, D-21029 Hamburg (Germany)

2012-02-01T23:59:59.000Z

192

Gamma-Ray Lines from Radiative Dark Matter Decay  

E-Print Network (OSTI)

The decay of dark matter particles which are coupled predominantly to charged leptons has been proposed as a possible origin of excess high-energy positrons and electrons observed by cosmic-ray telescopes PAMELA and Fermi LAT. Even though the dark matter itself is electrically neutral, the tree-level decay of dark matter into charged lepton pairs will generically induce radiative two-body decays of dark matter at the quantum level. Using an effective theory of leptophilic dark matter decay, we calculate the rates of radiative two-body decays for scalar and fermionic dark matter particles. Due to the absence of astrophysical sources of monochromatic gamma rays, the observation of a line in the diffuse gamma-ray spectrum would constitute a strong indication of a particle physics origin of these photons. We estimate the intensity of the gamma-ray line that may be present in the energy range of a few TeV if the dark matter decay interpretation of the leptonic cosmic-ray anomalies is correct and comment on observational prospects of present and future Imaging Cherenkov Telescopes, in particular the CTA.

Mathias Garny; Alejandro Ibarra; David Tran; Christoph Weniger

2010-11-16T23:59:59.000Z

193

Bremsstrahlung gamma rays from light Dark Matter  

E-Print Network (OSTI)

We discuss the often-neglected role of bremsstrahlung processes on the interstellar gas in computing indirect signatures of Dark Matter (DM) annihilation in the Galaxy, particularly for light DM candidates in the phenomenologically interesting O(10) GeV mass range. Especially from directions close to the Galactic Plane, the expected gamma-ray spectrum is altered via two effects: directly, by the photons emitted in the bremsstrahlung process on the interstellar gas by energetic electrons which are among the DM annihilation byproducts; indirectly, by the modification of the same electron spectrum, due to the additional energy loss process in the diffusion-loss equation (e.g. the resulting inverse Compton emission is altered). We quantify the importance of the bremsstrahlung emission in the GeV energy range, showing that it is the dominant component of the gamma-ray spectrum for some cases. We also find that, in regions in which bremsstrahlung dominates energy losses, the related gamma-ray emission is only moderately sensitive to possible large variations in the gas density. Still, we stress that, for computing precise spectra in the (sub-)GeV range, it is important to obtain a reliable description of the inner Galaxy gas distribution as well as to compute self-consistently the gamma emission and the solution to the diffusion-loss equation. For example, these are crucial issues to quantify and interpret meaningfully gamma-ray map `residuals' in terms of (light) DM annihilations.

Marco Cirelli; Pasquale D. Serpico; Gabrijela Zaharijas

2013-07-26T23:59:59.000Z

194

Reducing 68Ge Background in Dark Matter Experiments  

SciTech Connect

Experimental searches for dark matter include experiments with sub-0.5 keV-energy threshold high purity germanium detectors. Experimental efforts, in partnership with the CoGeNT Collaboration operating at the Soudan Underground Laboratory, are focusing on energy threshold reduction via noise abatement, reduction of backgrounds from cosmic ray generated isotopes, and ubiquitous environmental radioactive sources. The most significant cosmic ray produced radionuclide is 68Ge. This paper evaluates reducing this background by freshly mining and processing germanium ore. The most probable outcome is a reduction of the background by a factor of two, and at most a factor of four. A very cost effective alternative is to obtain processed Ge as soon as possible and store it underground for 18 months.

Kouzes, Richard T.; Orrell, John L.

2011-03-01T23:59:59.000Z

195

Presence of Dark Energy and Dark Matter : Does Cosmic Acceleration signifies a Weak Gravitational collapse?  

E-Print Network (OSTI)

In this work the collapsing process of a spherically symmetric star, made of dust cloud, in the background of dark energy is studied for two different gravity theories separately, i.e., DGP Brane gravity and Loop Quantum gravity. Two types of dark energy fluids, namely, Modified Chaplygin gas and Generalised Cosmic Chaplygin gas are considered for each model. Graphs are drawn to characterize the nature and the probable outcome of gravitational collapse. A comparative study is done between the collapsing process in the two different gravity theories. It is found that in case of dark matter, there is a great possibility of collapse and consequent formation of Black hole. In case of dark energy possibility of collapse is far lesser compared to the other cases, due to the large negative pressure of dark energy component. There is an increase in mass of the cloud in case of dark matter collapse due to matter accumulation. The mass decreases considerably in case of dark energy due to dark energy accretion on the cloud. In case of collapse with a combination of dark energy and dark matter, it is found that in the absence of interaction there is a far better possibility of formation of black hole in DGP brane model compared to Loop quantum cosmology model.

Prabir Rudra; Ritabrata Biswas; Ujjal Debnath

2012-04-03T23:59:59.000Z

196

Collapse Dynamics of a Star of Dark Matter and Dark Energy  

E-Print Network (OSTI)

In this work, we study the collapse dynamics of an inhomogeneous spherically symmetric star made of dark matter (DM) and dark energy (DE). The dark matter is taken in the form of a dust cloud while anisotropic fluid is chosen as the candidate for dark energy. It is investigated how dark energy modifies the collapsing process and is examined whether dark energy has any effect on the Cosmic Censorship Conjecture. The collapsing star is assumed to be of finite radius and the space time is divided into three distinct regions $\\Sigma$ and $V^{\\pm}$, where $\\Sigma$ represents the boundary of the star and $V^{-}(V^{+})$ denotes the interior (exterior) of the star. The junction conditions for matching $V^{\\pm}$ over $\\Sigma$ are specified. Role of Dark energy in the formation of apparent horizon is studied and central singularity is analyzed.

Subenoy Chakraborty; Tanwi Bandyopadhyay

2006-09-12T23:59:59.000Z

197

Low mass dark matter and invisible Higgs width in darkon models  

Science Conference Proceedings (OSTI)

The Standard Model (SM) plus a real gauge-singlet scalar field dubbed darkon (SM+D) is the simplest model possessing a weakly interacting massive particle (WIMP) dark matter candidate. In this model, the parameters are constrained from dark matter relic density and direct searches. The fact that interaction between darkon and SM particles is only mediated by a Higgs boson exchange may lead to significant modifications to the Higgs boson properties. If the dark matter mass is smaller than half of the Higgs boson mass, then a Higgs boson can decay into a pair of darkons resulting in a large invisible branching ratio. The Higgs boson will be searched for at the LHC and may well be discovered in the near future. If a Higgs boson with a small invisible decay width will be found, the SM+D model with small dark matter mass will be in trouble. We find that by extending the SM+D to a two Higgs doublet model plus a darkon (THDM+D) it is possible to have a Higgs boson with a small invisible branching ratio and at the same time the dark matter can have a low mass. We also comment on other implications of this model.

Cai Yi; Ren Bo [INPAC, Department of Physics, Shanghai Jiao Tong University, Shanghai (China); He Xiaogang [INPAC, Department of Physics, Shanghai Jiao Tong University, Shanghai (China); Department of Physics and Center for Theoretical Sciences, National Taiwan University, Taipei, Taiwan (China)

2011-04-15T23:59:59.000Z

198

Understanding the Fundamental Properties of Dark Matter & Dark Energy in Structure formation and Cosmology  

Science Conference Proceedings (OSTI)

This program is concerned with developing and verifying the validityof observational methods for constraining the properties of dark matter and dark energy in the universe. Excellent progress has been made in comparing observational projects involving weak gravitational lensing using both ground and space-based instruments, in further constraining the nature of dark matter via precise measures of its distribution in clusters of galaxies using strong gravitational lensing, in demonstrating the possible limitations of using distant supernovae in future dark energy missions, and in investigating the requirement for ground-based surveys of baryonic acoustic oscillations.

Ellis, Richard, S.

2008-02-01T23:59:59.000Z

199

In the OSTI Collections: Dark Matter and Dark Energy | OSTI, US Dept of  

Office of Scientific and Technical Information (OSTI)

Dark Matter and Dark Energy Dark Matter and Dark Energy Recent observations of the universe, combined with Einstein's theory of general relativity, indicate that most of the universe consists of entities very different from the matter and energy long familiar to us. These previously unknown entities are beginning to be explored on several fronts, many through Department of Energy sponsorship. Albert Einstein's theory of relativity describes space and time as observer-dependent aspects of a single absolute entity (spacetime). According to the theory, just as a two-dimensional surface can be curved, four-dimensional spacetime is also curved, with the curvature at different places and times being partly determined by how matter (or equivalently, energy) is distributed within it. Where curvature is lacking, matter will

200

Study of alpha background in a dark matter detector  

E-Print Network (OSTI)

Alpha background, specifically from radon and its progeny in the uranium and thorium chains, has been a major issue in dark matter detectors. This work focuses on alpha background presence in the DMTPC experiment by examining ...

Yegoryan, Hayk

2010-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "dark matter searches" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


201

Neutrino dark matter candidate in fourth generation scenarios  

E-Print Network (OSTI)

We overview the constraints on the 4th-generation neutrino dark matter candidate and investigate a possible way to make it a viable dark matter candidate. Given the LEP constraints tell us that the 4th-generation neutrino has to be rather heavy (> M_Z/2), in sharp contrast to the other three neutrinos, the underlying nature of the 4th-generation neutrino is expected to be different. We suggest that an additional gauge symmetry B-4L_4 distinguishes it from the Standard Model's three lighter neutrinos and this also facilitates promotion of the 4th-generation predominantly right-handed neutrino to a good cold dark matter candidate. It provides distinguishable predictions for the dark matter direct detection and the Large Hadron Collider experiments.

Hye-Sung Lee; Zuowei Liu; Amarjit Soni

2011-05-17T23:59:59.000Z

202

DMTPC: A dark matter detector with directional sensitivity  

E-Print Network (OSTI)

By correlating nuclear recoil directions with the Earth's direction of motion through the Galaxy, a directional dark matter detector can unambiguously detect Weakly Interacting Massive Particles (WIMPs), even in the presence ...

Battat, James

203

Direct Detection of Sub-GeV Dark Matter  

SciTech Connect

Direct detection strategies are proposed for dark matter particles with MeV to GeV mass. In this largely unexplored mass range, dark matter scattering with electrons can cause single-electron ionization signals, which are detectable with current technology. Ultraviolet photons, individual ions, and heat are interesting alternative signals. Focusing on ionization, we calculate the expected dark matter scattering rates and estimate the sensitivity of possible experiments. Backgrounds that may be relevant are discussed. Theoretically interesting models can be probed with existing technologies, and may even be within reach using ongoing direct detection experiments. Significant improvements in sensitivity should be possible with dedicated experiments, opening up a window to new regions in dark matter parameter space.

Essig, Rouven; Mardon, Jeremy; Volansky, Tomer

2012-03-20T23:59:59.000Z

204

Merger Rates of Dark-Matter Haloes  

E-Print Network (OSTI)

We derive analytic merger rates for dark-matter haloes within the framework of the Extended Press-Schechter (EPS) formalism. These rates become self-consistent within EPS once we realize that the typical merger in the limit of a small time-step involves more than two progenitors, contrary to the assumption of binary mergers adopted in earlier studies. We present a general method for computing merger rates that span the range of solutions permitted by the EPS conditional mass function, and focus on a specific solution that attempts to match the merger rates in N-body simulations. The corrected EPS merger rates are more accurate than the earlier estimates of Lacey & Cole, by ~20% for major mergers and by up to a factor of ~3 for minor mergers of mass ratio 1:10^4. Based on the revised merger rates, we provide a new algorithm for constructing Monte-Carlo EPS merger trees, that could be useful in Semi-Analytic Modeling. We provide analytic expressions and plot numerical results for several quantities that are very useful in studies of galaxy formation. This includes (a) the rate of mergers of a given mass ratio per given final halo, (b) the fraction of mass added by mergers to a halo, and (c) the rate of mergers per given main progenitor. The creation and destruction rates of haloes serve for a self-consistency check. Our method for computing merger rates can be applied to conditional mass functions beyond EPS, such as those obtained by the ellipsoidal collapse model or extracted from $N$-body simulations.

Eyal Neistein; Avishai Dekel

2008-02-04T23:59:59.000Z

205

Astrophysical manifestations of clumps of cold dark matter  

SciTech Connect

Small-scale structures (clumps) of dark matter may manifest themselves owing to the annihilation of dark-matter particles in them as pointlike gamma-ray sources. In view of this, investigation into respective effects on the basis of data on unidentified pointlike gamma-ray sources is of importance. It is shown that the existing uncertainties in the description of physical properties of dark-matter particles (their annihilation cross section) and in the distribution of their density in the clumps are of crucial importance; therefore, an analysis of data from the observation of pointlike gamma-ray sources makes it possible to impose constraints on the values of respective uncertain parameters (that is, to single out preferable ones). It is considered that the rate of annihilation of dark-matter particles in the clumps may be enhanced both owing to a higher density and owing to the growth of the cross section at low relative velocities of dark-matter particles in the clumps. In particular, dark-matter particles may have self-interaction of the Coulomb type, and this leads to the enhancement of the annihilation rate because of the Sommerfeld-Sakharov effect. It is shown that the heavy-neutrino model featuring an extra interaction can explain partly Fermi and EGRET data on unidentified pointlike gamma-ray sources. It is indicated that the motion of gamma-ray sources over the celestial sphere can be noticed for several clumps within several years of observations.

Belotsky, K. M., E-mail: k-belotsky@yandex.ru; Kirillov, A. A., E-mail: kirillov-aa@yandex.ru; Khlopov, M. Yu., E-mail: khlopov@apc.univ-paris7.fr [National Research Nuclear University MEPhI (Russian Federation)

2013-04-15T23:59:59.000Z

206

Rippled Cosmological Dark Matter from Damped Oscillating Newton Constant  

E-Print Network (OSTI)

Let the reciprocal Newton 'constant' be an apparently non-dynamical Brans-Dicke scalar field damped oscillating towards its General Relativistic VEV. We show, without introducing additional matter fields or dust, that the corresponding cosmological evolution averagely resembles, in the Jordan frame, the familiar dark radiation -> dark matter -> dark energy domination sequence. The fingerprints of our theory are fine ripples, hopefully testable, in the FRW scale factor; they die away at the General Relativity limit. The possibility that the Brans-Dicke scalar also serves as the inflaton is favorably examined.

Aharon Davidson

2004-09-15T23:59:59.000Z

207

Observational constraints on holographic tachyonic dark energy in interaction with dark matter  

E-Print Network (OSTI)

We discuss an interacting tachyonic dark energy model in the context of the holographic principle. The potential of the holographic tachyon field in interaction with dark matter is constructed. The model results are compared with CMB shift parameter, baryonic acoustic oscilations, lookback time and the Constitution supernovae sample. The coupling constant of the model is compatible with zero, but dark energy is not given by a cosmological constant.

Sandro M. R. Micheletti

2009-12-20T23:59:59.000Z

208

On the growth of perturbations in interacting dark energy and dark matter fluids  

E-Print Network (OSTI)

The covariant generalizations of the background dark sector coupling suggested in G. Mangano, G. Miele and V. Pettorino, Mod. Phys. Lett. A 18, 831 (2003) are considered. The evolution of perturbations is studied with detailed attention to interaction rate that is proportional to the product of dark matter and dark energy densities. It is shown that some classes of models with coupling of this type do not suffer from early time instabilities in strong coupling regime.

N. A. Koshelev

2009-12-01T23:59:59.000Z

209

DARK MATTER SUBHALOS IN THE URSA MINOR DWARF GALAXY  

SciTech Connect

Through numerical simulations, we study the dissolution timescale of the Ursa Minor cold stellar clump, due to the combination of phase-mixing and gravitational encounters with compact dark substructures in the halo of Ursa Minor. We compare two scenarios: one where the dark halo is made up by a smooth mass distribution of light particles and one where the halo contains 10% of its mass in the form of substructures (subhalos). In a smooth halo, the stellar clump survives for a Hubble time provided that the dark matter halo has a large core. In contrast, when the point-mass dark substructures are added, the clump survives for barely {approx}1.5 Gyr. These results suggest a strong test of the {Lambda}-cold dark matter scenario at dwarf galaxy scale.

Lora, V.; Just, A.; Grebel, E. K. [Astronomisches Rechen-Institut, Zentrum fuer Astronomie der Universitaet Heidelberg, Moenchhofstr. 12-14, D-69120 Heidelberg (Germany); Sanchez-Salcedo, F. J., E-mail: vlora@ari.uni-heidelberg.de [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, AP 70-264, 04510 D.F. (Mexico)

2012-09-20T23:59:59.000Z

210

DARK MATTER AND DARK ENERGY AS EFFECTS OF QUANTUM GRAVITY Max I. Fomitchev1  

E-Print Network (OSTI)

DARK MATTER AND DARK ENERGY AS EFFECTS OF QUANTUM GRAVITY Max I. Fomitchev1 Submitted March 12th , 2004 ABSTRACT I present a theory of quantum gravity based on the principle of gravitational energy fluctuations. Gravitational energy fluctuations ­ gravitons ­ are responsible for elastic scattering

Giles, C. Lee

211

Modified Gravitational Theory as an Alternative to Dark Energy and Dark Matter  

E-Print Network (OSTI)

The problem of explaining the acceleration of the expansion of the universe and the observational and theoretical difficulties associated with dark matter and dark energy are discussed. The possibility that Einstein gravity does not correctly describe the large-scale structure of the universe is considered and an alternative gravity theory is proposed as a possible resolution to the problems.

Moffat, J W

2004-01-01T23:59:59.000Z

212

From Dark Energy to Dark Matter via Non-Minimal Coupling  

E-Print Network (OSTI)

Toy cosmological models based on non-minimal coupling between gravity and scalar dilaton-like field are presented in the framework of Palatini formalism. They have the following property: preceding to a given cosmological epoch is a dark energy epoch with an accelerated expansion. The next (future) epoch becomes dominated by some kind of dark matter.

A. Borowiec

2008-12-23T23:59:59.000Z

213

A brief note on how to unify dark matter, dark energy, and inflation  

E-Print Network (OSTI)

A scenario in which inflation, dark energy and dark matter can be unified into a single scalar field, the inflaton field $\\phi$, is studied. The inflaton is identified with the sneutrino, the scalar partner of the heavy neutrino. We determine the conditions needed for avoiding the gravitino problem and not having negligible plasma effects and we obtain the allowed range for the sneutrino coupling.

Grigoris Panotopoulos

2007-06-15T23:59:59.000Z

214

Gamma-ray constraints on dark-matter annihilation to electroweak gauge and Higgs bosons  

E-Print Network (OSTI)

Dark-matter annihilation into electroweak gauge and Higgs bosons results in $\\gamma$-ray emission. We use observational upper limits on the fluxes of both line and continuum $\\gamma$-rays from the Milky Way Galactic Center and from Milky Way dwarf companion galaxies to set exclusion limits on allowed dark-matter masses. (Generally, Galactic Center $\\gamma$-ray line search limits from the Fermi-LAT and the H.E.S.S. experiments are most restrictive.) Our limits apply under the following assumptions: a) the dark matter species is a cold thermal relic with present mass density equal to the measured dark-matter density of the universe; b) dark-matter annihilation to standard-model particles is described in the non-relativistic limit by a single effective operator ${\\cal O} \\propto J_{DM}\\cdot J_{SM}$, where $J_{DM}$ is a standard-model singlet current consisting of dark-matter fields (Dirac fermions or complex scalars), and $J_{SM}$ is a standard-model singlet current consisting of electroweak gauge and Higgs bosons; and c) the dark-matter mass is in the range 5 GeV to 20 TeV. We consider, in turn, the 34 possible operators with mass dimension 8 or lower with non-zero s-wave annihilation channels satisfying the above assumptions. Our limits are presented in a large number of figures, one for each of the 34 possible operators; these limits can be grouped into 13 classes determined by the field content and structure of the operators. We also identify three classes of operators (coupling to the Higgs and $SU(2)_L$ gauge bosons) that can supply a 130 GeV line with the desired strength to fit the putative line signal in Fermi data, while saturating the relic density and satisfying all other indirect constraints we consider.

Michael A. Fedderke; Edward W. Kolb; Tongyan Lin; Lian-Tao Wang

2013-10-22T23:59:59.000Z

215

Sensitivity of the IceCube neutrino detector to dark matter annihilating in dwarf galaxies  

SciTech Connect

In this paper, we compare the relative sensitivities of gamma-ray and neutrino observations to the dark matter annihilation cross section in leptophilic models such as have been designed to explain PAMELA data. We investigate whether the high energy neutrino telescope IceCube will be competitive with current and upcoming searches by gamma-ray telescopes, such as the Atmospheric Cerenkov Telescopes (H.E.S.S., VERITAS, and MAGIC), or the Fermi Gamma-Ray Space Telescope, in detecting or constraining dark matter particles annihilating in dwarf spheroidal galaxies. We find that after 10 years of observation of the most promising nearby dwarfs, IceCube will have sensitivity comparable to the current sensitivity of gamma-ray telescopes only for very heavy (m{sub X} > or approx. 7 TeV) or relatively light (m{sub X} < or approx. 200 GeV) dark matter particles which annihilate primarily to {mu}{sup +{mu}-}. If dark matter particles annihilate primarily to {tau}{sup +{tau}-}, IceCube will have superior sensitivity only for dark matter particle masses below the 200 GeV threshold of current Atmospheric Cerenkov Telescopes. If dark matter annihilations proceed directly to neutrino-antineutrino pairs a substantial fraction of the time, IceCube will be competitive with gamma-ray telescopes for a much wider range of dark matter masses. K. F. would like to thank the Aspen Center for Physics and the Texas Cosmology Center, and P. S. would like to thank MCTP.

Sandick, Pearl [Theory Group and Texas Cosmology Center, University of Texas at Austin, Texas 78712 (United States); Spolyar, Douglas [Center for Particle Astrophysics, Fermi National Accelerator Laboratory, Batavia, Illinois 60510 (United States); Department of Physics, University of California, Santa Cruz, California 95064 (United States); Buckley, Matthew [Department of Physics, California Institute of Technology, Pasadena, California 91125 (United States); Freese, Katherine [Michigan Center for Theoretical Physics, University of Michigan, Ann Arbor, Michigan 48109 (United States); Hooper, Dan [Center for Particle Astrophysics, Fermi National Accelerator Laboratory, Batavia, Illinois 60510 (United States); Department of Astronomy and Astrophysics, University of Chicago, Chicago, Illinois 60638 (United States)

2010-04-15T23:59:59.000Z

216

Effects of dark matter annihilation on the first stars  

E-Print Network (OSTI)

We study the evolution of the first stars in the universe (Population III) from the early pre-Main Sequence until the end of helium burning in the presence of WIMP dark matter annihilation inside the stellar structure. The two different mechanisms that can provide this energy source are the contemporary contraction of baryons and dark matter, and the capture of WIMPs by scattering off the gas with subsequent accumulation inside the star. We find that the first mechanism can generate an equilibrium phase, previously known as a "dark star", which is transient and present in the very early stages of pre-MS evolution. The mechanism of scattering and capture acts later, and can support the star virtually forever, depending on environmental characteristic of the dark matter halo and on the specific WIMP model.

F. Iocco; A. Bressan; E. Ripamonti; R. Schneider; A. Ferrara; P. Marigo

2008-09-14T23:59:59.000Z

217

Is the Interacting Dark Matter Scenario an Alternative to Dark Energy ?  

E-Print Network (OSTI)

We study the global dynamics of the universe within the framework of the Interacting Dark Matter (IDM) scenario. Assuming that the dark matter obeys the collisional Boltzmann equation, we can derive analytical solutions of the global density evolution, which can accommodate an accelerated expansion, equivalent to either the {\\em quintessence} or the standard $\\Lambda$ models. We also find realistic solutions in which the present time is located after the inflection point.

Basilakos, S

2008-01-01T23:59:59.000Z

218

A Modified Generalized Chaplygin Gas as the Unified Dark Matter-Dark Energy Revisited  

E-Print Network (OSTI)

A modified generalized Chaplygin gas (MGCG) is considered as the unified dark matter-dark energy revisited. The character of MGCG is endued with the dual role, which behaves as matter at early times and as an quiessence dark energy at late times. The equation of state for MGCG is $p=-\\alpha\\rho/(1+\\alpha)-\\vartheta(z)\\rho^{-\\alpha}/(1+\\alpha) $, where $\\vartheta(z)=-[\\rho_{0c}(1+z)^{3}]^{(1+\\alpha)}(1-\\Omega_{0B})^{\\alpha}\\{\\alpha\\Omega_{0DM}+ \\Omega_{0DE}[\\omega_{DE}+\\alpha(1+\\omega_{DE})](1+z)^{3\\omega_{DE}(1+\\alpha)}\\}$. Some cosmological quantities, such as the densities of different components of the universe $\\Omega_{i}$ ($i$ respectively denotes baryons, dark matter and dark energy) and the deceleration parameter $q$, are obtained. The present deceleration parameter $q_{0}$, the transition redshift $z_{T}$ and the redshift $z_{eq}$, which describes the epoch when the densities in dark matter and dark energy are equal, are also calculated. To distinguish MGCG from others, we then apply the Statefinder diagnostic. Later on, the parameters ($\\alpha$ and $\\omega_{DE}$) of MGCG are constrained by combination of the sound speed $c^{2}_{s}$, the age of the universe $t_{0}$, the growth factor $m$ and the bias parameter $b$. It yields $\\alpha=-3.07^{+5.66}_{-4.98}\\times10^{-2}$ and $\\omega_{DE}=-1.05^{+0.06}_{-0.11}$. Through the analysis of the growth of density perturbations for MGCG, it is found that the energy will transfer from dark matter to dark energy which reach equal at $z_{eq}\\sim 0.48$ and the density fluctuations start deviating from the linear behavior at $z\\sim 0.25$ caused by the dominance of dark energy.

Xue-Mei Deng

2011-10-10T23:59:59.000Z

219

ENVIRONMENT DEPENDENCE OF DARK MATTER HALOS IN SYMMETRON MODIFIED GRAVITY  

Science Conference Proceedings (OSTI)

We investigate the environment dependence of dark matter halos in the symmetron modified gravity scenario. The symmetron is one of three known mechanisms for screening a fifth force and thereby recovering general relativity in dense environments. The effectiveness of the screening depends on both the mass of the object and the environment it lies in. Using high-resolution N-body simulations we find a significant difference, which depends on the halo's mass and environment, between the lensing and dynamical masses of dark matter halos similar to the f(R) modified gravity. The symmetron can however yield stronger signatures due to a freedom in the strength of coupling to matter.

Winther, Hans A.; Mota, David F. [Institute of Theoretical Astrophysics, University of Oslo, NO-0315 Oslo (Norway); Li Baojiu [ICC, Department of Physics, University of Durham, South Road, Durham DH1 3LE (United Kingdom)

2012-09-10T23:59:59.000Z

220

The Unified Equation of State for Dark Matter and Dark Energy  

E-Print Network (OSTI)

We assume that dark matter and dark energy satisfy the unified equation of state: p = B(z)?, with p = pdE, ? = ?dm + ?dE, where the pressure of dark matter pdm = 0 has been taken into account. A special function B = ? A (1+z) ? is presented, which can well describe the evolution of the universe. In this model, the universe will end up with a Big Rip. By further simple analysis, we know other choices of the function B can also describe the universe but lead to a different doomsday.

Wei Wang; Yuanxing Gui; Suhong Zhang; Guanghai Guo; Ying Shao

2005-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "dark matter searches" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


221

Dark Matter and Dark Energy from the solution of the strong CP problem  

E-Print Network (OSTI)

The Peccei Quinn (PQ) solution of the strong CP problem requires the existence of axions, which are a viable candidate for Dark Matter. Here we show that, if the Nambu Goldstone potential of the PQ model is replaced by a potential V(|\\Phi|) admitting a tracker solution, the scalar field |\\Phi| can account for Dark Energy, while the phase of \\Phi yields axion Dark Matter. Such Dark Matter and Dark Energy turn out to be weakly coupled. If V is a SUGRA potential, the model essentially depends on a single parameter, the energy scale \\Lambda. Once we set \\Lambda \\simeq 10^{10} GeV, at the quark--hadron transition, |\\Phi| naturally passes through values suitable to solve the strong CP problem, later growing to values providing fair amounts of Dark Matter and Dark Energy. In this model, the linear growth factor, from recombination to now, is quite close to \\LambdaCDM. The selected \\Lambda value can be an indication of the scale where the soft breaking of SUSY occurred.

Roberto Mainini; Silvio A. Bonometto

2004-06-04T23:59:59.000Z

222

Dark energy interacting with neutrinos and dark matter: a phenomenological theory  

E-Print Network (OSTI)

A model for a flat homogeneous and isotropic Universe composed of dark energy, dark matter, neutrinos, radiation and baryons is analyzed. The fields of dark matter and neutrinos are supposed to interact with the dark energy. The dark energy is considered to obey either the van der Waals or the Chaplygin equations of state. The ratio between the pressure and the energy density of the neutrinos varies with the red-shift simulating massive and non-relativistic neutrinos at small red-shifts and non-massive relativistic neutrinos at high red-shifts. The model can reproduce the expected red-shift behaviors of the deceleration parameter and of the density parameters of each constituent. The recent astronomical measurements of type-IA supernovae [1, 2, 3, 4] and the analysis of the power spectrum of the CMBR [5, 6, 7, 8, 9] provided strong evidence for a present accelerated

G. M. Kremer

2008-01-01T23:59:59.000Z

223

DARK MATTER AS AN ACTIVE GRAVITATIONAL AGENT IN CLOUD COMPLEXES  

SciTech Connect

We study the effect that the dark matter background (DMB) has on the gravitational energy content and, in general, on the star formation efficiency (SFE) of a molecular cloud (MC). We first analyze the effect that a dark matter halo, described by the Navarro-Frenk-White density profile, has on the energy budget of a spherical, homogeneous cloud located at different distances from the halo center. We found that MCs located in the innermost regions of a massive galaxy can feel a contraction force greater than their self-gravity due to the incorporation of the potential of the galaxy's dark matter halo. We also calculated analytically the gravitational perturbation that an MC produces over a uniform DMB (uniform at the scales of an MC) and how this perturbation will affect the evolution of the MC itself. The study shows that the star formation in an MC will be considerably enhanced if the cloud is located in a dense and low velocity dark matter environment. We confirm our results by measuring the SFE in numerical simulations of the formation and evolution of MCs within different DMBs. Our study indicates that there are situations where the dark matter's gravitational contribution to the evolution of the MCs should not be neglected.

Suarez-Madrigal, Andres; Ballesteros-Paredes, Javier; Colin, Pedro; D'Alessio, Paola, E-mail: a.suarez@crya.unam.mx [Centro de Radioastronomia y Astrofisica, Universidad Nacional Autonoma de Mexico, Apdo. Postal 72-3 (Xangari), Morelia, Michocan, Mexico C.P. 58089 (Mexico)

2012-04-01T23:59:59.000Z

224

Dark matter growth and baryon bias in an accelerating universe  

E-Print Network (OSTI)

We investigate the exact analytic solutions for the growths of the dark matter and the baryon in sub-horizon scale. The growth of the dark matter $\\delta_{\\DM}$ is related to that of the halos. Thus, the exact solution for the growth of the dark matter is important to obtain the proper properties of dark matter halos. However, the dark energy model dependence of $\\delta_{\\DM}$ is confused with the $\\delta_{\\DM}$ dependence on $\\Omega_{m}^{0}$. Thus, the careful investigation is necessary for the $\\delta_{\\DM}$ dependence on dark energy models. We also obtain the exact solution of the growth of the baryon $\\delta_{\\B}$ which can be used to obtain the baryon bias factor $b(a)$. This might be able to be observed in intracluster gas or in Lyman-$\\alpha$ clouds. However, $b(a)$ is quite model independent. Recently, we obtained the exact analytic solution for the growing mode solution of the matter linear density perturbation $\\delta$ on sub-horizon scale for general dark energy model \\cite{SK}. This solution is not same as the well known approximate analytic solution \\cite{Waga}. The exact analytic solution shows the same evolution behavior of the growth factor obtained numerically. However, the exact solution is simple and useful for the extension to other models including modified gravity theories. Furthermore, it guides to the fact that the growth index parameter depends on both models $\\omega_{\\de}$ and $\\Omega_{m}^{0}$ and thus we need to be careful for applying the fitting formulae to the general models \\cite{WS}. The exact analytic solutions for the growth factor will provide the more accurate tools for the weak lensing, the number density of clusters, their mass and etc.

Seokcheon Lee

2009-06-17T23:59:59.000Z

225

Boldly Illuminating Biology's "Dark Matter"  

NLE Websites -- All DOE Office Websites (Extended Search)

14, 2013 14, 2013 Boldly Illuminating Biology's "Dark Matter" Is space really the final frontier, or are the greatest mysteries closer to home? In cosmology, dark matter is said to account for the majority of mass in the universe, however its presence is inferred by indirect effects rather than detected through telescopes. The biological equivalent is "microbial dark matter," that pervasive yet practically invisible infrastructure of life on the planet, which can have profound influences on the most significant environmental processes from plant growth and health, to nutrient cycles in terrestrial and marine environments, the global carbon cycle, and possibly even climate processes. By employing next generation DNA sequencing of genomes isolated from single cells, great

226

(Lack of) lensing constraints on cluster dark matter profiles  

E-Print Network (OSTI)

Using stellar dynamics and strong gravitational lensing as complementary probes, Sand et al. (2002, 2003) have recently claimed strong evidence for shallow dark matter density profiles in several lensing clusters, which may conflict with predictions of the Cold Dark Matter paradigm. However, systematic uncertainties in the analysis weaken the constraints. By re-analyzing their data, we argue that the tight constraints claimed by Sand et al., were driven by prior assumptions. Relaxing the assumptions, we find that no strong constraints may be derived on the dark matter inner profile from the Sand et al. data; we find satisfactory fits (with reasonable parameters) for a wide range of inner slopes 0 < beta < 1.4. Useful constraints on the mass distributions of lensing clusters can still be obtained, but they require moving beyond mere measurements of lensing critical radii into the realm of detailed lens modeling.

Neal Dalal; Charles R. Keeton

2003-12-02T23:59:59.000Z

227

Nonextensive theory of dark matter and gas density profiles  

E-Print Network (OSTI)

Pronounced core-halo patterns of dark matter and gas density profiles, observed in relaxed galaxies and clusters, were hitherto fitted by empirical power-laws. On the other hand, similar features are well known from astrophysical plasma environments, subject to long-range interactions, modeled in the context of nonextensive entropy generalization. We link nonextensive statistics to the problem of density distributions in large-scale structures and provide fundamentally derived density profiles, representing accurately the characteristics of both, dark matter and hot plasma distributions, as observed or generated in simulations. The bifurcation of the density distribution into a kinetic dark matter and thermodynamic gas branch turns out as natural consequence of the theory and is controlled by a single parameter kappa, measuring physically the degree of coupling within the system. Consequently, it is proposed to favor nonextensive distributions, derived from the fundamental physical context of entropy generali...

Leubner, M P

2005-01-01T23:59:59.000Z

228

Stable Higgs Bosons - new candidate for cold dark matter -  

E-Print Network (OSTI)

The Higgs boson is in the backbone of the standard model of electroweak interactions. It must exist in some form for achieving unification of interactions. In the gauge-Higgs unification scenario the Higgs boson becomes a part of the extra-dimensional component of gauge fields. The Higgs boson becomes absolutely stable in a class of the gauge-Higgs unification models, serving as a promising candidate for cold dark matter in the universe. The observed relic abundance of cold dark matter is obtained with the Higgs mass around 70 GeV. The Higgs-nucleon scattering cross section is found to be close to the recent CDMS II and XENON10 bounds in the direct detection of dark matter. In collider experiments stable Higgs bosons are produced in a pair, appearing as missing energies and momenta so that the way of detecting Higgs bosons must be altered.

Yutaka Hosotani

2010-03-31T23:59:59.000Z

229

Stable Higgs Bosons - new candidate for cold dark matter  

SciTech Connect

The Higgs boson is in the backbone of the standard model of electroweak interactions. It must exist in some form for achieving unification of interactions. In the gauge-Higgs unification scenario the Higgs boson becomes a part of the extra-dimensional component of gauge fields. The Higgs boson becomes absolutely stable in a class of the gauge-Higgs unification models, serving as a promising candidate for cold dark matter in the universe. The observed relic abundance of cold dark matter is obtained with the Higgs mass around 70 GeV. The Higgs-nucleon scattering cross section is found to be close to the recent CDMS II XENON10 bounds in the direct detection of dark matter. In collider experiments stable Higgs bosons are produced in a pair, appearing as missing energies momenta so that the way of detecting Higgs bosons must be altered.

Hosotani, Yutaka [Department of Physics, Osaka University, Toyonaka Osaka 560-0043 (Japan)

2010-08-12T23:59:59.000Z

230

A DERIVATION OF (HALF) THE DARK MATTER DISTRIBUTION FUNCTION  

SciTech Connect

All dark matter structures appear to follow a set of universalities, such as phase-space density or velocity anisotropy profiles; however, the origin of these universalities remains a mystery. Any equilibrated dark matter structure can be fully described by two functions, namely the radial and tangential velocity distribution functions (VDFs), and once these two are understood we will understand all the observed universalities. Here, we demonstrate that if we know the radial VDF then we can derive and understand the tangential VDF. This is based on simple dynamical arguments about properties of collisionless systems. We use a range of controlled numerical simulations to demonstrate the accuracy of this result. We therefore boil the question of the dark matter structural properties down to understanding the radial VDF.

Hansen, Steen H.; Sparre, Martin, E-mail: hansen@dark-cosmology.dk, E-mail: sparre@dark-cosmology.dk [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen (Denmark)

2012-09-01T23:59:59.000Z

231

Isospin-Violating Dark Matter and Neutrinos From the Sun  

E-Print Network (OSTI)

We study the indirect detection of dark matter through neutrino flux from their annihilation in the center of the Sun, in a class of theories where the dark matter-nucleon spin-independent interactions break the isospin symmetry. We point out that, while the direct detection bounds with heavy targets like Xenon are weakened and reconciled with the positive signals in DAMA and CoGeNT experiments, the indirect detection using neutrino telescopes can impose a relatively stronger constraint and brings tension to such explanation, if the annihilation is dominated by heavy quark or $\\tau$-lepton final states. As a consequence, the qualified isospin violating dark matter candidate has to preferably annihilate into light flavors.

Shao-Long Chen; Yue Zhang

2011-06-20T23:59:59.000Z

232

Declarative Modeling and Bayesian Inference of Dark Matter Halos  

E-Print Network (OSTI)

Probabilistic programming allows specification of probabilistic models in a declarative manner. Recently, several new software systems and languages for probabilistic programming have been developed on the basis of newly developed and improved methods for approximate inference in probabilistic models. In this contribution a probabilistic model for an idealized dark matter localization problem is described. We first derive the probabilistic model for the inference of dark matter locations and masses, and then show how this model can be implemented using BUGS and Infer.NET, two software systems for probabilistic programming. Finally, the different capabilities of both systems are discussed. The presented dark matter model includes mainly non-conjugate factors, thus, it is difficult to implement this model with Infer.NET.

Kronberger, Gabriel

2013-01-01T23:59:59.000Z

233

Distribution of annihilation luminosities in dark matter substructure  

SciTech Connect

We calculate the probability distribution function (PDF) of the expected annihilation luminosities of dark matter subhalos as a function of subhalo mass and distance from the Galactic center using a semianalytical model of halo evolution. We find that the PDF of luminosities is relatively broad, exhibiting a spread of as much as an order of magnitude at fixed subhalo mass and halo-centric distance. The luminosity PDF allows for simple construction of mock samples of {gamma}-ray luminous subhalos and assessment of the variance in the predicted {gamma}-ray signals from dark matter annihilation. Other applications include quantifying the variance among the expected luminosities of dwarf spheroidal galaxies, assessing the level at which dark matter annihilation can be a contaminant in the expected {gamma}-ray signal from other astrophysical sources, as well as estimating the level at which nearby subhalos can contribute to the antimatter flux.

Koushiappas, Savvas M. [Department of Physics, Brown University, 182 Hope Street, Providence, Rhode Island 02912 (United States); Zentner, Andrew R. [Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 (United States); Kravtsov, Andrey V. [Kavli Institute for Cosmological Physics, University of Chicago, Chicago, Illinois 60637 (United States); Enrico Fermi Institute, University of Chicago, Chicago, Illinois 60637 (United States); Department of Astronomy and Astrophysics, University of Chicago, Chicago, Illinois 60605 (United States)

2010-10-15T23:59:59.000Z

234

Co-existence of Gravity and Antigravity: The Unification of Dark Matter and Dark Energy  

E-Print Network (OSTI)

Massive gravity with second and fourth derivatives is shown to give both attractive and repulsive gravities. In contrast to the attractive gravity correlated with the energy-momentum tensor, the repulsive gravity is related to a fixed mass $m_x$, which equals a spin-dependent factor $f_\\sigma$ times the graviton mass. Therefore, particles with energy below $m_x$ are both dark matter and dark energy: Their overall gravity is attractive with normal matter but repulsive among themselves. Detailed analyses reveal that this unified dark scenario can properly account for the observed dark matter/energy phenomena: galaxy rotation curves, transition from early cosmic deceleration to recent acceleration; and naturally overcome other dark scenarios' difficulties: the substructure and cuspy core problems, the difference of dark halo distributions in galaxies and clusters, and the cosmic coincidence. Very interestingly, Dirac particles have $f_\\sigma=1/\\sqrt 2$, all bosonic matter particles have $f_\\sigma=0$, and the only exceptional boson is the graviton itself, which may have $f_\\sigma>1$.

Xiang-Song Chen

2005-06-03T23:59:59.000Z

235

A new test of the light dark matter hypothesis  

E-Print Network (OSTI)

Detection of a surprisingly high flux of positron annihilation radiation from the inner galaxy has motivated the proposal that dark matter is made of weakly interacting light particles (possibly as light as the electron). This scenario is extremely hard to test in current high energy physics experiments. Here, however, we demonstrate that the current value of the electron anomalous magnetic moment already has the required precision to unambiguously test the light dark matter hypothesis. If confirmed, the implications for astrophysics are far-reaching.

Celine Boehm; Joseph Silk

2007-08-21T23:59:59.000Z

236

Standard model Higgs boson-inflaton and dark matter  

Science Conference Proceedings (OSTI)

The standard model Higgs boson can serve as the inflaton field of slow roll inflationary models provided it exhibits a large nonminimal coupling with the gravitational scalar curvature. The Higgs boson self interactions and its couplings with a standard model singlet scalar serving as the source of dark matter are then subject to cosmological constraints. These bounds, which can be more stringent than those arising from vacuum stability and perturbative triviality alone, still allow values for the Higgs boson mass which should be accessible at the LHC. As the Higgs boson coupling to the dark matter strengthens, lower values of the Higgs boson mass consistent with the cosmological data are allowed.

Clark, T. E.; Liu Boyang; Love, S. T.; Veldhuis, T. ter [Department of Physics, Purdue University, West Lafayette, Indiana 47907-2036 (United States); Department of Physics and Astronomy, Macalester College, Saint Paul, Minnesota 55105-1899 (United States)

2009-10-01T23:59:59.000Z

237

Photonic portal to the sterile world of cold dark matter  

E-Print Network (OSTI)

We assume that the cold dark matter consists of spin-1/2 and spin-0 particles described by a bispinor field \\psi and a scalar field \\phi, sterile from all Standard Model charges (in contrast, neutralinos, supersymmetric candidates for cold dark matter, are not sterile from weak Standard Model charges). We propose, however, that such a sterile world can contact with our Standard Model world not only through gravity but also through a portal provided by photons coupled to sterile particles by means of two very weak effective interactions -(f/M^2)\\phi F^{\\mu\

Wojciech Krolikowski

2007-12-04T23:59:59.000Z

238

DMTPC: A dark matter detector with directional sensitivity  

E-Print Network (OSTI)

By correlating nuclear recoil directions with the Earth's direction of motion through the Galaxy, a directional dark matter detector can unambiguously detect Weakly Interacting Massive Particles (WIMPs), even in the presence of backgrounds. Here, we describe the Dark Matter Time-Projection Chamber (DMTPC) detector, a TPC filled with CF4 gas at low pressure (0.1 atm). Using this detector, we have measured the vector direction (head-tail) of nuclear recoils down to energies of 100 keV with an angular resolution of Mexico.

Battat, J B R; Caldwell, T; Dujmic, D; Dushkin, A; Fisher, P; Golub, F; Goyal, S; Henderson, S; Inglis, A; Lanza, R; López, J; Kaboth, A; Kohse, G; Monroe, J; Sciolla, G; Skvorodnev, B N; Tomita, H; Vanderspek, R; Wellenstein, H; Yamamoto, R

2009-01-01T23:59:59.000Z

239

New physics at low energies and dark matter-dark energy transmutation  

E-Print Network (OSTI)

A field theory is proposed where the regular fermionic matter and the dark fermionic matter can be different states of the same "primordial" fermion fields. In regime of the fermion densities typical for normal particle physics, the primordial fermions split into three families identified with regular fermions. When fermion energy density becomes comparable with dark energy density, the theory allows transition to new type of states. The possibility of such Cosmo-Low Energy Physics (CLEP) states is demonstrated by means of solutions of the field theory equations describing FRW universe filled with homogeneous scalar field and uniformly distributed nonrelativistic neutrinos. Neutrinos in CLEP state are drawn into cosmological expansion by means of dynamically changing their own parameters. One of the features of the fermions in CLEP state is that in the late time universe their masses increase as a^{3/2} (a=a(t) is the scale factor). The energy density of the cold dark matter consisting of neutrinos in CLEP state scales as a sort of dark energy; this cold dark matter possesses negative pressure and for the late time universe its equation of state approaches that of the cosmological constant. The total energy density of such universe is less than it would be in the universe free of fermionic matter at all.

E. I. Guendelman; A. B. Kaganovich

2004-04-14T23:59:59.000Z

240

The necessity of dark matter in MOND within galactic scales  

E-Print Network (OSTI)

To further test MOdified Newtonian Dynamics (MOND) on galactic scales -- originally proposed to explain the rotation curves of disk galaxies without dark matter -- we study a sample of six strong gravitational lensing early-type galaxies from the CASTLES database. To determine whether dark matter is present in these galaxies, we compare the total mass (from lensing) with the stellar mass content (from a comparison of photometry and stellar population synthesis). We find that strong gravitational lensing on galactic scales requires a significant amount of dark matter, even within MOND. On such scales a 2 eV neutrino cannot explain this excess matter -- in contrast with recent claims to explain the lensing data of the bullet cluster. The presence of dark matter is detected in regions with a higher acceleration than the characteristic MONDian scale of $\\sim 10^{-10}$m/s$^2$. This is a serious challenge to MOND unless the proper treatment of lensing is qualitatively different (possibly to be developed within a consistent theory such as TeVeS).

Ignacio Ferreras; Mairi Sakellariadou; Muhammad Furqaan Yusaf

2007-09-20T23:59:59.000Z

Note: This page contains sample records for the topic "dark matter searches" from the National Library of EnergyBeta (NLEBeta).
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241

Limits on Stellar Objects as the Dark Matter of Our Halo: Nonbaryonic Dark Matter Seems to be Required  

E-Print Network (OSTI)

The nature of the dark matter in the Halo of our Galaxy remains a mystery. Arguments are presented that the dark matter does not consist of ordinary stellar or substellar objects, i.e., the dark matter is not made of faint stars, brown dwarfs, white dwarfs, or neutron stars. In fact, faint stars and brown dwarfs constitute no more than a few percent of the mass of our Galaxy, and stellar remnants must satisfy $\\Omega_{WD} \\leq 3 \\times 10^{-3} h^{-1}$, where $h$ is the Hubble constant in units of 100 km/s Mpc^{-1}. On theoretical grounds one is then pushed to more exotic explanations. Indeed a nonbaryonic component in the Halo seems to be required.

Katherine Freese; Brian Fields; David Graff

1999-04-28T23:59:59.000Z

242

Constraining Dark Matter Models from a Combined Analysis of Milky Way Satellites with the Fermi Large Area Telescope  

SciTech Connect

Satellite galaxies of the Milky Way are among the most promising targets for dark matter searches in gamma rays. We present a search for dark matter consisting of weakly interacting massive particles, applying a joint likelihood analysis to 10 satellite galaxies with 24 months of data of the Fermi Large Area Telescope. No dark matter signal is detected. Including the uncertainty in the dark matter distribution, robust upper limits are placed on dark matter annihilation cross sections. The 95% confidence level upper limits range from about 10{sup -26} cm{sup 3} s{sup -1} at 5 GeV to about 5 x 10{sup -23} cm{sup 3} s{sup -1} at 1 TeV, depending on the dark matter annihilation final state. For the first time, using gamma rays, we are able to rule out models with the most generic cross section ({approx}3 x 10{sup -26} cm{sup 3} s{sup -1} for a purely s-wave cross section), without assuming additional boost factors.

Ackermann, M.; Ajello, M.; /Stanford U., HEPL /Taiwan, Natl. Taiwan U. /SLAC; Albert, A.; /Taiwan, Natl. Taiwan U. /Ohio State U.; Atwood, W.B.; /UC, Santa Cruz; Baldini, L.; /INFN, Pisa; Ballet, J.; /DAPNIA, Saclay; Barbiellini, G.; /INFN, Trieste /Trieste U.; Bastieri, D.; /INFN, Padua /Padua U.; Bechtol, K.; /Stanford U., HEPL /Taiwan, Natl. Taiwan U. /SLAC; Bellazzini, R.; /INFN, Pisa; Berenji, B.; Blandford, R.D.; Bloom, E.D.; /Stanford U., HEPL /Taiwan, Natl. Taiwan U. /SLAC; Bonamente, E.; /INFN, Perugia /Perugia U.; Borgland, A.W.; /Stanford U., HEPL /Taiwan, Natl. Taiwan U. /SLAC; Bregeon, J.; /INFN, Pisa; Brigida, M.; /Bari Polytechnic /INFN, Bari; Bruel, P.; /Ecole Polytechnique; Buehler, R.; /Stanford U., HEPL /Taiwan, Natl. Taiwan U. /SLAC; Burnett, T.H.; /Washington U., Seattle; Buson, S.; /INFN, Padua /Padua U. /ICE, Bellaterra /Stanford U., HEPL /Taiwan, Natl. Taiwan U. /SLAC /INFN, Rome /Rome U. /IASF, Milan /IASF, Milan /DAPNIA, Saclay /INFN, Perugia /Perugia U. /Stanford U., HEPL /Taiwan, Natl. Taiwan U. /SLAC /Artep Inc. /Stanford U., HEPL /Taiwan, Natl. Taiwan U. /SLAC /ASDC, Frascati /Perugia U. /Stanford U., HEPL /Taiwan, Natl. Taiwan U. /SLAC /Montpellier U. /Stockholm U. /Stockholm U., OKC /ASDC, Frascati /ASDC, Frascati /Udine U. /INFN, Trieste /Bari Polytechnic /INFN, Bari /Naval Research Lab, Wash., D.C. /Stanford U., HEPL /Taiwan, Natl. Taiwan U. /SLAC /Montpellier U. /Bari Polytechnic /INFN, Bari /Ecole Polytechnique /NASA, Goddard /Hiroshima U. /Stanford U., HEPL /Taiwan, Natl. Taiwan U. /SLAC /Bari Polytechnic /INFN, Bari /INFN, Bari /ASDC, Frascati /NASA, Goddard /INFN, Perugia /Perugia U. /Bari Polytechnic /INFN, Bari /Bologna Observ. /Stanford U., HEPL /Taiwan, Natl. Taiwan U. /SLAC /DAPNIA, Saclay /Alabama U., Huntsville; /more authors..

2012-09-14T23:59:59.000Z

243

GUT and supersymmetry at the LHC and in dark matter  

SciTech Connect

Conventional SO(10) models involve more than one scale for a complete breaking of the GUT symmetry requiring further assumptions on the VEVs of the Higgs fields that enter in the breaking to achieve viable models. Recent works where the breaking can be accomplished at one scale are discussed. These include models with just a pair of 144+144 of Higgs fields. Further extensions of this idea utilizing 560+560 of Higgs representations allow both the breaking at one scale, as well as accomplish a natural doublet-triplet splitting via the missing partner mechanism. More generally, we discuss the connection of high scale models to low energy physics in the context of supergravity grand unification. Here we discuss a natural solution to the little hierarchy problem and also discuss the implications of the LHC data for supersymmetry. It is shown that the LHC data implies that most of the parameter space of supergravity models consistent with the data lie on the Hyperbolic Branch of radiative breaking of the electroweak symmetry and more specifically on the Focal Surface of the Hyperbolic Branch. A discussion is also given of the implications of recent LHC data on the Higgs boson mass for the discovery of supersymmetry and for the search for dark matter.

Nath, Pran [Department of Physics, Northeastern University, Boston, MA 02115 (United States)

2012-07-27T23:59:59.000Z

244

Visible and dark matter in M 31 - II. A dynamical model and dark matter density distribution  

E-Print Network (OSTI)

In the present paper we derive the density distribution of dark matter (DM) in a well-observed nearby disc galaxy, the Andromeda galaxy. From photometrical and chemical evolution models constructed in the first part of the study (Tamm, Tempel & Tenjes 2007 (arXiv:0707.4375), hereafter Paper I) we can calculate the mass distribution of visible components. In the dynamical model we calculate stellar rotation velocities along the major axis and velocity dispersions along the major, minor and intermediate axes of the galaxy. Comparing the calculated values with the collected observational data, we find the amount of DM, which must be added to reach an agreement with the observed rotation and dispersion data. We conclude that within the uncertainties, the DM distributions by Moore, Burkert, isothermal, Navarro, Frenk & White (NFW) and Navarro et al. 2004 (N04) fit with observations. The NFW and N04 density distributions give the best fit with observations. The total mass of M 31 with the NFW DM distributio...

Tempel, Elmo; Tenjes, Peeter

2007-01-01T23:59:59.000Z

245

hep-th/0411025 Cosmology with Interaction between Phantom Dark Energy and Dark Matter and the Coincidence Problem  

E-Print Network (OSTI)

We study a cosmological model in which phantom dark energy has an interaction with dark matter by introducing a term in the equations of motion of dark energy and dark matter. Such a term is parameterized by a product of a dimensionless coupling function ?, Hubble parameter and the energy density of dark matter, and it manifests an energy flow between the dark energy and dark matter. We discuss two cases, one is that the state parameter ?e of the dark energy keeps as a constant; the other is that the dimensionless coupling function ? remains as a constant. We investigate the effect of the interaction on the evolution of the universe, the total lifetime of the universe, and the ratio of the period when the universe is in the coincidence state to its total lifetime. It turns out the interaction will produce significant deviation from the case without the interaction.

Rong-gen Cai; Anzhong Wang

2004-01-01T23:59:59.000Z

246

Section on Prospects for Dark Matter Detection of the White Paper on the Status and Future of Ground-Based TeV Gamma-Ray Astronomy  

E-Print Network (OSTI)

This is a report on the findings of the dark matter science working group for the white paper on the status and future of TeV gamma-ray astronomy. The white paper was commissioned by the American Physical Society, and the full white paper can be found on astro-ph (arXiv:0810.0444). This detailed section discusses the prospects for dark matter detection with future gamma-ray experiments, and the complementarity of gamma-ray measurements with other indirect, direct or accelerator-based searches. We conclude that any comprehensive search for dark matter should include gamma-ray observations, both to identify the dark matter particle (through the charac- teristics of the gamma-ray spectrum) and to measure the distribution of dark matter in galactic halos.

Buckley, J; Bertone, G; Byrum, K; Fegan, S; Ferrer, F; Gondolo, P; Hall, J; Hooper, D; Horan, D; Koushiappas, S; Krawczynski, H; Le Bohec, S; Profumo, S; Silk, J; Tait, T; Vasilev, V; Wagner, R; Wakely, S; Wood, M; Zaharijas, G

2008-01-01T23:59:59.000Z

247

Section on Prospects for Dark Matter Detection of the White Paper on the Status and Future of Ground-Based TeV Gamma-Ray Astronomy  

E-Print Network (OSTI)

This is a report on the findings of the dark matter science working group for the white paper on the status and future of TeV gamma-ray astronomy. The white paper was commissioned by the American Physical Society, and the full white paper can be found on astro-ph (arXiv:0810.0444). This detailed section discusses the prospects for dark matter detection with future gamma-ray experiments, and the complementarity of gamma-ray measurements with other indirect, direct or accelerator-based searches. We conclude that any comprehensive search for dark matter should include gamma-ray observations, both to identify the dark matter particle (through the charac- teristics of the gamma-ray spectrum) and to measure the distribution of dark matter in galactic halos.

J. Buckley; E. A. Baltz; G. Bertone; K. Byrum; S. Fegan; F. Ferrer; P. Gondolo; J. Hall; D. Hooper; D. Horan; S. Koushiappas; H. Krawczynski; S. LeBohec; S. Profumo; J. Silk; T. Tait; V. Vassiliev; R. Wagner; S. Wakely; M. Wood; G. Zaharijas

2008-12-03T23:59:59.000Z

248

Section on prospects for dark matter detection of the white paper on the status and future of ground-based TeV gamma-ray astronomy.  

SciTech Connect

This is a report on the findings of the dark matter science working group for the white paper on the status and future of TeV gamma-ray astronomy. The white paper was commissioned by the American Physical Society, and the full white paper can be found on astro-ph (arXiv:0810.0444). This detailed section discusses the prospects for dark matter detection with future gamma-ray experiments, and the complementarity of gamma-ray measurements with other indirect, direct or accelerator-based searches. We conclude that any comprehensive search for dark matter should include gamma-ray observations, both to identify the dark matter particle (through the characteristics of the gamma-ray spectrum) and to measure the distribution of dark matter in galactic halos.

Byrum, K.; Horan, D.; Tait, T.; Wanger, R.; Zaharijas, G.; Buckley , J.; Baltz, E. A.; Bertone, G.; Dingus, B.; Fegan, S.; Ferrer, F.; Gondolo, P.; Hall, J.; Hooper, D.; Horan, D.; Koushiappas, S.; Krawczynksi, H.; LeBohec, S.; Pohl, M.; Profumo, S.; Silk , J; Vassilev, V.; Wood , M.; Wakely, S.; High Energy Physics; FNAL; Univ. of St. Louis; Stanford Univ.; Insti. d' Astrophysique; LANL; Univ. of California; Washington Univ.; Univ. of Utah; Brown Univ.; Oxford Univ.; Iowa State Univ.; Univ. of Chicago

2009-05-13T23:59:59.000Z

249

LHC constraints on light neutralino dark matter in the MSSM  

E-Print Network (OSTI)

Light neutralino dark matter can be achieved in the Minimal Supersymmetric Standard Model if staus are rather light, with mass around 100 GeV. We perform a detailed analysis of the relevant supersymmetric parameter space, including also the possibility of light selectons and smuons, and of light higgsino- or wino-like charginos. In addition to the latest limits from direct and indirect detection of dark matter, ATLAS and CMS constraints on electroweak-inos and on sleptons are taken into account using a "simplified models" framework. Measurements of the properties of the Higgs boson at 125 GeV, which constrain amongst others the invisible decay of the Higgs boson into a pair of neutralinos, are also implemented in the analysis. We show that viable neutralino dark matter can be achieved for masses as low as 15 GeV. In this case, light charginos close to the LEP bound are required in addition to light right-chiral staus. Significant deviations are observed in the couplings of the 125 GeV Higgs boson. These constitute a promising way to probe the light neutralino dark matter scenario in the next run of the LHC.

Genevieve Belanger; Guillaume Drieu La Rochelle; Beranger Dumont; Rohini M. Godbole; Sabine Kraml; Suchita Kulkarni

2013-08-16T23:59:59.000Z

250

Dark Matter Constraints from a Cosmic Index of Refraction  

E-Print Network (OSTI)

The dark-matter candidates of particle physics invariably possess electromagnetic interactions, if only via quantum fluctuations. Taken en masse, dark matter can thus engender an index of refraction which deviates from its vacuum value. Its presence is signaled through frequency-dependent effects in the propagation and attenuation of light. We discuss theoretical constraints on the expansion of the index of refraction with frequency, the physical interpretation of the terms, and the particular observations needed to isolate its coefficients. This, with the advent of new opportunities to view gamma-ray bursts at cosmological distance scales, gives us a new probe of dark matter and a new possibility for its direct detection. As a first application we use the time delay determined from radio afterglow observations of distant gamma-ray bursts to realize a direct limit on the electric-charge-to-mass ratio of dark matter of |varepsilon|/M < 1 x 10^{-5} eV^{-1} at 95% CL.

S. Gardner; D. C. Latimer

2009-04-10T23:59:59.000Z

251

TeV Dark Matter detection by Atmospheric Cerenkov Telescopes  

E-Print Network (OSTI)

Ground based Atmospheric Cerenkov Telescopes have recently unveiled a TeV gamma-ray signal from the direction of the Galactic Centre. We examine whether these gamma-rays, observed by the VERITAS, CANGAROO-II and HESS collaborations, may arise from annihilations of dark matter particles. Emission from nearby dwarf spheroidals, such as Sagittarius, could provide a test of this scenario.

Francesc Ferrer

2005-05-19T23:59:59.000Z

252

COSMIC MICROWAVE BACKGROUND CONSTRAINTS OF DECAYING DARK MATTER PARTICLE PROPERTIES  

SciTech Connect

If a component of cosmological dark matter is made up of massive particles-such as sterile neutrinos-that decay with cosmological lifetime to emit photons, the reionization history of the universe would be affected, and cosmic microwave background anisotropies can be used to constrain such a decaying particle model of dark matter. The optical depth depends rather sensitively on the decaying dark matter particle mass m{sub dm}, lifetime {tau}{sub dm}, and the mass fraction of cold dark matter f that they account for in this model. Assuming that there are no other sources of reionization and using the Wilkinson Microwave Anisotropy Probe 7-year data, we find that 250 eV {approx}< m{sub dm} {approx}< 1 MeV, whereas 2.23 Multiplication-Sign 10{sup 3} yr {approx}< {tau}{sub dm}/f {approx}< 1.23 Multiplication-Sign 10{sup 18} yr. The best-fit values for m{sub dm} and {tau}{sub dm}/f are 17.3 keV and 2.03 Multiplication-Sign 10{sup 16} yr, respectively.

Yeung, S.; Chan, M. H.; Chu, M.-C., E-mail: mcchu@phy.cuhk.edu.hk [Department of Physics and Institute of Theoretical Physics, Chinese University of Hong Kong, Shatin, New Territories (Hong Kong)

2012-08-20T23:59:59.000Z

253

Dark Matter, Quantum Gravity, Vacuum Energy, and Lorentz Invariance  

E-Print Network (OSTI)

We discuss the problems of dark matter, quantum gravity, and vacuum energy within the context of a theory for which Lorentz invariance is not postulated, but instead emerges as a natural consequence in the physical regimes where it has been tested.

Roland E. Allen

2001-10-23T23:59:59.000Z

254

Probing EWSB Naturalness in Unified SUSY Models with Dark Matter  

E-Print Network (OSTI)

We have studied Electroweak Symmetry Breaking (EWSB) fine-tuning in the context of two unified Supersymmetry scenarios: the Constrained Minimal Supersymmetric Model (CMSSM) and models with Non-Universal Higgs Masses (NUHM), in light of current and upcoming direct detection dark matter experiments. We consider both those models that satisfy a one-sided bound on the relic density of neutralinos, $\\Omega_{\

Amsel, Stephen; Sandick, Pearl

2011-01-01T23:59:59.000Z

255

Dark matter constraints from a cosmic index of refraction  

SciTech Connect

The dark matter candidates of particle physics invariably possess electromagnetic interactions, if only via quantum fluctuations. Taken en masse, dark matter can thus engender an index of refraction which deviates from its vacuum value. Its presence is signaled through frequency-dependent effects in the propagation and attenuation of light. We discuss theoretical constraints on the expansion of the index of refraction with frequency, the physical interpretation of the terms, and the particular observations needed to isolate its coefficients. This, with the advent of new opportunities to view gamma-ray bursts at cosmological distance scales, gives us a new probe of dark matter and a new possibility for its direct detection. As a first application we use the time delay determined from radio afterglow observations of distant gamma-ray bursts to realize a direct limit on the electric charge-to-mass ratio of dark matter of |{epsilon}|/M<1x10{sup -5} eV{sup -1} at 95% C.L.

Gardner, Susan [Center for Particle Astrophysics and Theoretical Physics Department, Fermi National Accelerator Laboratory, Batavia, Illinois 60510 (United States); Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506-0055 (United States); Latimer, David C. [Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506-0055 (United States)

2010-09-15T23:59:59.000Z

256

Spontaneously Induced Gravity: From Rippled Dark Matter to Einstein Corpuscles  

E-Print Network (OSTI)

Suppose General Relativity, provocatively governed by a dimensional coupling constant, is a spontaneously induced theory of Gravity. Invoking Zee's mechanism, we represent the reciprocal Newton constant by a Brans Dicke scalar field, and let it damped oscillating towards its General Relativistic VEV. The corresponding cosmological evolution, in the Jordan frame, averagely resembles the familiar dark radiation -> dark matter -> dark energy domination sequence. The fingerprints of the theory are fine ripples, hopefully testable, in the FRW scale factor; they die away at the strict General Relativity limit. Also derived is the spherically symmetric static configuration associated with spontaneously induced General Relativity. At the stiff scalar potential limit, the exterior Schwarzschild solution is recovered. However, due to level crossing at the would have been horizon, it now connects with a novel dark core characterized by a locally varying Newton constant. The theory further predicts light Einstein-style gravitational corpuscles (elementary particles?) which become point-like at the GR-limit.

Aharon Davidson; Ilya Gurwich

2006-06-13T23:59:59.000Z

257

A Concept for A Dark Matter Detector Using Liquid Helium-4  

E-Print Network (OSTI)

Direct searches for light dark matter particles (mass $<10$ GeV) are especially challenging because of the low energies transferred in elastic scattering to typical heavy nuclear targets. We investigate the possibility of using liquid Helium-4 as a target material, taking advantage of the favorable kinematic matching of the Helium nucleus to light dark matter particles. Monte Carlo simulations are performed to calculate the charge, scintillation, and triplet helium molecule signals produced by recoil He ions, for a variety of energies and electric fields. We show that excellent background rejection can be achieved based on the ratios between different signal channels. We also present some concepts for a liquid-helium-based dark matter detector. Key to the proposed approach is the use of a large electric field to extract electrons from the event site, and the amplification of this charge signal, through proportional scintillation, liquid electroluminescence, or roton emission. The sensitivity of the proposed detector to light dark matter particles is estimated for various electric fields and light collection efficiencies.

Wei Guo; Daniel N. McKinsey

2013-02-03T23:59:59.000Z

258

Is Dark Matter Heavy Because of Electroweak Symmetry Breaking? Revisiting Heavy Neutrinos  

E-Print Network (OSTI)

A simple and well-motivated explanation for the origin of dark matter is that it consists of thermal relic particles that get their mass entirely through electroweak symmetry breaking. The simplest models implementing this possibility predict a dark matter candidate that consists of a mixture of two Dirac neutrinos with opposite isospin, and so has suppressed coupling to the Z. These models predict dark matter masses of m_{DM}~45 GeV or m_{DM}~90-95 GeV and WIMP-neutron spin-independent cross sections \\sigma_{WIMP-n}~10^{-6}-10^{-8} pb. Current direct dark matter searches are probing a portion of the parameter space of these models while future experiments sensitive to \\sigma_{WIMP-n}~10^{-8} pb will probe the remainder. An enhancement of the galactic halo gamma ray and positron flux coming from annihilations of these particles is also expected across the ~1-100 GeV range. The framework further suggests an environmental explanation of the hierarchy between the weak and Planck scales and of the small value of the cosmological constant relative to the weak scale.

Philip C. Schuster; Natalia Toro

2005-06-08T23:59:59.000Z

259

Constraints on Bosonic Dark Matter From Observations of Old Neutron Stars  

E-Print Network (OSTI)

Baryon interactions with bosonic dark matter are constrained by the potential for dark matter-rich neutron stars to collapse into black holes. We consider the effect of dark matter self-interactions and dark matter annihilation on these bounds, and treat the evolution of the black hole after formation. We show that, for non-annihilating dark matter, these bounds extend up to $m_X \\sim 10^{5-7}$ GeV, depending on the strength of self-interactions. However, these bounds are completely unconstraining for annihilating bosonic dark matter with an annihilation cross-section of $ \\gtrsim 10^{-38} {\\rm cm^3 /s}$. Dark matter decay does not significantly affect these bounds. We thus show that bosonic dark matter accessible to near-future direct detection experiments must participate in an annihilation or self-interaction process to avoid black hole collapse constraints from very old neutron stars.

Joseph Bramante; Keita Fukushima; Jason Kumar

2013-01-01T23:59:59.000Z

260

The case for a directional dark matter detector and the status of current experimental efforts  

E-Print Network (OSTI)

We present the case for a dark matter detector with directional sensitivity. This document was developed at the 2009 CYGNUS workshop on directional dark matter detection, and contains contributions from theorists and ...

Battat, James

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261

Environment Dependence of Dark Matter Halos in Symmetron Modified Gravity  

E-Print Network (OSTI)

We investigate the environment dependence of dark matter halos in the symmetron modified gravity scenario. The symmetron is one of three known mechanisms for screening a fifth-force and thereby recovering General Relativity in dense environments. The effectiveness of the screening depends on both the mass of the object and the environment it lies in. Using high-resolution N-body simulations we find a significant difference, which depends on the halos mass and environment, between the lensing and dynamical masses of dark matter halos similar to the f(R) modified gravity. The symmetron can however yield stronger signatures due to a freedom in the strength of the coupling to matter.

Hans A. Winther; David F. Mota; Baojiu Li

2011-10-28T23:59:59.000Z

262

Visible and dark matter in M 31 - II. A dynamical model and dark matter density distribution  

E-Print Network (OSTI)

In the present paper we derive the density distribution of dark matter (DM) in a well-observed nearby disc galaxy, the Andromeda galaxy. From photometrical and chemical evolution models constructed in the first part of the study (Tamm, Tempel & Tenjes 2007 (arXiv:0707.4375), hereafter Paper I) we can calculate the mass distribution of visible components (the bulge, the disc, the stellar halo, the outer diffuse stellar halo). In the dynamical model we calculate stellar rotation velocities along the major axis and velocity dispersions along the major, minor and intermediate axes of the galaxy assuming triaxial velocity dispersion ellipsoid. Comparing the calculated values with the collected observational data, we find the amount of DM, which must be added to reach an agreement with the observed rotation and dispersion data. We conclude that within the uncertainties, the DM distributions by Moore, Burkert, Navarro, Frenk & White (NFW) and the Einasto fit with observations nearly at all distances. The NFW and Einasto density distributions give the best fit with observations. The total mass of M 31 with the NFW DM distribution is 1.19*10^12 M_sun, the ratio of the DM mass to the visible mass is 10.0. For the Einasto DM distribution, these values are 1.28*10^12 M_sun and 10.8. The ratio of the DM mass to the visible mass inside the Holmberg radius is 1.75 for the NFW and the Einasto distributions. For different cuspy DM distributions, the virial mass is in a range 6.9-7.9*10^11 M_sun and the virial radius is ~150 kpc. The DM mean densities inside 10 pc for cusped models are 33 and 16 M_sun pc^-3 for the NFW and the Einasto profiles, respectively. For the cored Burkert profile, this value is 0.06 M_sun pc^-3.

Elmo Tempel; Antti Tamm; Peeter Tenjes

2007-07-30T23:59:59.000Z

263

A Quantum Cosmology: No Dark Matter, Dark Energy nor Accelerating Universe  

E-Print Network (OSTI)

We show that modelling the universe as a pre-geometric system with emergent quantum modes, and then constructing the classical limit, we obtain a new account of space and gravity that goes beyond Newtonian gravity even in the non-relativistic limit. This account does not require dark matter to explain the spiral galaxy rotation curves, and explains as well the observed systematics of black hole masses in spherical star systems, the bore hole $g$ anomalies, gravitational lensing and so on. As well the dynamics has a Hubble expanding universe solution that gives an excellent parameter-free account of the supernovae and gamma-ray-burst red-shift data, without dark energy or dark matter. The Friedmann-Lema\\^{i}tre-Robertson-Walker (FLRW) metric is derived from this dynamics, but is shown not satisfy the General Relativity based Friedmann equations. It is noted that General Relativity dynamics only permits an expanding flat 3-space solution if the energy density in the pressure-less dust approximation is non-zero. As a consequence dark energy and dark matter are required in this cosmological model, and as well the prediction of a future exponential accelerating Hubble expansion. The FLRW $\\Lambda$CDM model data-based parameter values, $\\Omega_\\Lambda=0.73$, $\\Omega_{DM}=0.27$, are derived within the quantum cosmology model, but are shown to be merely artifacts of using the Friedmann equations in fitting the red-shift data.

Reginald T Cahill

2007-09-18T23:59:59.000Z

264

On the Origin of Gravity, Dark Energy and Matter.  

E-Print Network (OSTI)

Insights from black hole physics and developments in string theory strongly indicate that the gravity is derived from an underlying microscopic description in which it has no a priori meaning. Starting from first principles we argue that inertia and gravity are caused by the fact that phase space volume (or entropy) associated with the underlying microscopic system is influenced by the positions of material objects. Application of these ideas to cosmology leads to surprising new insights into the nature of dark energy and dark matter.

CERN. Geneva

2011-01-01T23:59:59.000Z

265

Statistical Physics of Dark and Normal Matter Distribution in Galaxy Formation : Dark Matter Lumps and Black Holes in Core and Halo of Galaxy  

E-Print Network (OSTI)

In unified field theory the cosmological model of the universe has supersymmetric fields. Supersymmetric particles as dark and normal matter in galaxy clusters have a phase separation. Dark matter in halos have a statistical physics equation of state. Neutralino particle gas with gravitation can have a collapse of dark matter lumps. A condensate phase due to boson creation by annhillation and exchange can occur at high densities. The collapse of the boson condensate, including neutralinos, into the Schwarzschild radius creates dark matter black holes. Microscopic dark matter black holes can evaporate with Hawking effect giving gamma ray bursts and create a spectrum of normal particles. The phase separation of normal and dark matter in galaxy clusters and inside galaxies is given by statistical physics.

Ajay Patwardhan

2008-05-15T23:59:59.000Z

266

CONSTRAINTS ON DARK MATTER ANNIHILATION IN CLUSTERS OF GALAXIES FROM DIFFUSE RADIO EMISSION  

SciTech Connect

Annihilation of dark matter can result in the production of stable Standard Model particles including electrons and positrons that, in the presence of magnetic fields, lose energy via synchrotron radiation, observable as radio emission. Galaxy clusters are excellent targets to search for or to constrain the rate of dark matter annihilation, as they are both massive and dark matter dominated. In this study, we place limits on dark matter annihilation in a sample of nearby clusters using upper limits on the diffuse radio emission, low levels of observed diffuse emission, or detections of radio mini-halos. We find that the strongest limits on the annihilation cross section are better than limits derived from the non-detection of clusters in the gamma-ray band by a factor of {approx}3 or more when the same annihilation channel and substructure model, but different best-case clusters, are compared. The limits on the cross section depend on the assumed amount of substructure, varying by as much as two orders of magnitude for increasingly optimistic substructure models as compared to a smooth Navarro-Frenk-White profile. In our most optimistic case, using the results of the Phoenix Project, we find that the derived limits reach below the thermal relic cross section of 3 Multiplication-Sign 10{sup -26} cm{sup 3} s{sup -1} for dark matter masses as large as 400 GeV, for the b b-bar annihilation channel. We discuss uncertainties due to the limited available data on the magnetic field structure of individual clusters. We also report the discovery of diffuse radio emission from the central 30-40 kpc regions of the groups M49 and NGC 4636.

Storm, Emma; Jeltema, Tesla E.; Profumo, Stefano [Department of Physics, University of California, 1156 High St., Santa Cruz, CA 95064 (United States); Rudnick, Lawrence [Minnesota Institute for Astrophysics, School of Physics and Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455 (United States)

2013-05-10T23:59:59.000Z

267

Difficulties for Compact Composite Object Dark Matter  

E-Print Network (OSTI)

It has been suggested ``that DM particles are strongly interacting composite macroscopically large objects ... made of well known light quarks (or ... antiquarks)." In doing so it is argued that these compact composite objects (CCOs) are ``natural explanations of many observed data, such as [the] 511 keV line from the bulge of our galaxy" observed by INTEGRAL and the excess of diffuse gamma-rays in the 1-20 MeV band observed by COMPTEL. Here we argue that the atmospheres of positrons that surround CCOs composed of di-antiquark pairs in the favoured Colour-Flavour-Locked superconducting state are sufficiently dense as to stringently limit the penetration of interstellar electrons incident upon them, resulting in an extreme suppression of previously estimated rates of positronium, and hence the flux of 511 keV photons resulting from their decays, and also in the rate of direct electron-positron annihilations, which yield the MeV photons proposed to explain the 1-20 MeV excess. We also demonstrate that even if a fraction of positrons somehow penetrated to the surface of the CCOs, the extremely strong electric fields generated from the bulk antiquark matter would result in the destruction of positronium atoms long before they decay.

Daniel T. Cumberbatch; Glenn D. Starkman; Joseph Silk

2006-06-18T23:59:59.000Z

268

Sneutrino dark matter: Symmetry protection and cosmic ray anomalies  

SciTech Connect

We present an R-parity conserving model of sneutrino dark matter within a Higgsphilic U(1){sup '} extension of the minimal supersymmetric standard model. In this theory, the {mu} parameter and light Dirac neutrino masses are generated naturally upon the breaking of the U(1){sup '} gauge symmetry. One of the right-handed sneutrinos is the lightest supersymmetric particle. The leptonic and hadronic decays of another sneutrino, taken to be the next-to-lightest superpartner, allow for a natural fit to the recent results reported by the PAMELA experiment. We perform a detailed calculation of the dark matter relic density in this scenario, and show that the model is consistent with the ATIC and Fermi LAT experiments.

Demir, Durmus A. [Department of Physics, Izmir Institute of Technology, IZTECH, TR35430 Izmir (Turkey); Everett, Lisa L. [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States); Frank, Mariana [Department of Physics, Concordia University, 7141 Sherbrooke St. West, Montreal, Quebec, H4B 1R6, (Canada); Selbuz, Levent [Department of Physics, Izmir Institute of Technology, IZTECH, TR35430 Izmir (Turkey); Department of Engineering Physics, Ankara University, TR06100 Ankara (Turkey); Turan, Ismail [Department of Physics, Concordia University, 7141 Sherbrooke St. West, Montreal, Quebec, H4B 1R6, (Canada); Ottawa-Carleton Institute of Physics, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario, K1S 5B6. (Canada)

2010-02-01T23:59:59.000Z

269

Radiative inverse seesaw neutrino mass and dark matter  

SciTech Connect

Seesaw mechanism provides a natural explanation of light neutrino masses through suppression of heavy seesaw scale. In inverse seesaw models the seesaw scale can be much lower than that in the usual seesaw models. If terms inducing seesaw masses are further induced by loop corrections, the seesaw scale can be lowered to be in the range probed by experiments at the LHC without fine tuning. This talk, presented by X-G He, discuss models constructed in a recent preprint by us (arxiv:201207.6308) in which neutrino masses are generated at two loop level through inverse seesaw mechanism. These models also naturally have dark matter candidates. Although the recent data from Xenon100 put stringent constraint on the models, they can be consistent with data on neutrino masses, mixing, dark matter relic density and direct detection.

Guo Gang [INPAC, Department of Physics and Shanghai Key Laboratory for Particle Physics and Cosmology Shanghai Jiao Tong University, Shanghai (China); He Xiaogang [INPAC, Department of Physics and Shanghai Key Laboratory for Particle Physics and Cosmology Shanghai Jiao Tong University, Shanghai (China) and Department of Physics, National Tsing Hua University, and NCTS, Hsinchu, Taiwan (China); Li Guannan [INPAC, Department of Physics and Shanghai Key Laboratory for Particle Physics and Cosmology Shanghai Jiao Tong University, Shanghai, Taiwan (China)

2013-05-23T23:59:59.000Z

270

Low scale left-right symmetry and warm dark matter  

SciTech Connect

We study the scenario which incorporates dark matter in the minimal left-right symmetric theory at the TeV scale. The only viable candidate is found to be the lightest right-handed neutrino with a mass of keV. In order to satisfy the dark matter relic abundance, the relic yield is diluted by late decays of the two heavier neutrinos. We point out that the QCD phase transition temperature coincidences with the typical freeze-out temperature governed by super-weak right-handed interactions. This helps to alleviate the problem of overproduction and a careful numerical study reveals a narrow window for the mass of the right-handed gauge boson, which is within the reach of the LHC.

Nemevsek, Miha [ICTP, Strada Costiera 11, 34151 Trieste (Italy)

2013-05-23T23:59:59.000Z

271

Spontaneous formation of double bars in dark matter dominated galaxies  

E-Print Network (OSTI)

Although nearly one-third of barred galaxies host an inner, secondary bar, the formation and evolution of double barred galaxies remain unclear. We show here an example model of a galaxy, dominated by a live dark matter halo, in which double bars form naturally, without requiring gas, and we follow its evolution for a Hubble time. The inner bar in our model galaxy rotates almost as slowly as the outer bar, and it can reach up to half of its length. The route to the formation of a double bar may be different from that of a single strong bar. Massive dark matter halo or dynamically hot stellar disc may play an important role in the formation of double bars and their subsequent evolution.

Saha, Kanak

2013-01-01T23:59:59.000Z

272

Extremely High Energy Neutrinos, Neutrino Hot Dark Matter, and the Highest Energy Cosmic Rays  

E-Print Network (OSTI)

Extremely high energy (up to 10**(22) eV) cosmic neutrino beams initiate high energy particle cascades in the background of relic neutrinos from the Big Bang. We perform numerical calculations to show that such cascades could contribute more than 10% to the observed cosmic ray flux above 10**(19) eV if neutrinos have masses in the electron volt range. The required intensity of primary neutrinos could be consistent with astrophysical models for their production if the maximum neutrino energy reaches to 10**(22) eV and the massive neutrino dark matter is locally clustered. Future observations of ultra high energy cosmic rays will lead to an indirect but practical search for neutrino dark matter.

Shigeru Yoshida; Guenter Sigl; Sangjin Lee

1998-08-14T23:59:59.000Z

273

Dynamics and constraints of the unified dark matter flat cosmologies  

SciTech Connect

We study the dynamics of the scalar field Friedmann-Lemaitre-Robertson-Walker flat cosmological models within the framework of the unified dark matter (UDM) scenario. In this model we find that the main cosmological functions such as the scale factor of the Universe, the scalar field, the Hubble flow, and the equation of state parameter are defined in terms of hyperbolic functions. These analytical solutions can accommodate an accelerated expansion, equivalent to either the dark energy or the standard {lambda} models. Performing a joint likelihood analysis of the recent supernovae type Ia data and the baryonic acoustic oscillations traced by the Sloan Digital Sky Survey galaxies, we place tight constraints on the main cosmological parameters of the UDM cosmological scenario. Finally, we compare the UDM scenario with various dark energy models namely {lambda} cosmology, parametric dark energy model and variable Chaplygin gas. We find that the UDM scalar field model provides a large and small scale dynamics which are in fair agreement with the predictions by the above dark energy models although there are some differences especially at high redshifts.

Basilakos, Spyros [Academy of Athens, Research Center for Astronomy and Applied Mathematics, Soranou Efesiou 4, GR-11527, Athens (Greece); Lukes-Gerakopoulos, Georgios [Academy of Athens, Research Center for Astronomy and Applied Mathematics, Soranou Efesiou 4, GR-11527, Athens (Greece); University of Athens, Department of Physics, Section of Astrophysics, Astronomy and Mechanics (Greece)

2008-10-15T23:59:59.000Z

274

Nonextensive theory of dark matter and gas density profiles  

E-Print Network (OSTI)

Pronounced core-halo patterns of dark matter and gas density profiles, observed in relaxed galaxies and clusters, were hitherto fitted by empirical power-laws. On the other hand, similar features are well known from astrophysical plasma environments, subject to long-range interactions, modeled in the context of nonextensive entropy generalization. We link nonextensive statistics to the problem of density distributions in large-scale structures and provide fundamentally derived density profiles, representing accurately the characteristics of both, dark matter and hot plasma distributions, as observed or generated in simulations. The bifurcation of the density distribution into a kinetic dark matter and thermodynamic gas branch turns out as natural consequence of the theory and is controlled by a single parameter kappa, measuring physically the degree of coupling within the system. Consequently, it is proposed to favor nonextensive distributions, derived from the fundamental physical context of entropy generalization and accounting for nonlocality and long-range interactions in gravitationally coupled systems, when modeling observed density profiles of astrophysical structures.

M. P. Leubner

2006-02-27T23:59:59.000Z

275

Solar neutrino physics: Sensitivity to light dark matter particles  

E-Print Network (OSTI)

Neutrinos are produced in several neutrino nuclear reactions of the proton-proton chain and carbon-nitrogen-oxygen cycle that take place at different radius of the Sun's core. Hence, measurements of solar neutrino fluxes provide a precise determination of the local temperature. The accumulation of non-annihilating light dark matter particles (with masses between 5 GeV and 16 GeV in the Sun produces a change in the local solar structure, namely, a decrease in the central temperature of a few percent. This variation depends on the properties of the dark matter particles, such as the mass of the particle and its spin-independent scattering cross-section on baryon-nuclei, specifically, the scattering with helium, oxygen, and nitrogen among other heavy elements. This temperature effect can be measured in almost all solar neutrino fluxes. In particular, by comparing the neutrino fluxes generated by stellar models with current observations, namely 8B neutrino fluxes, we find that non-annihilating dark matter particles with a mass smaller than 10 GeV and a spin-independent scattering cross-section with heavy baryon-nuclei larger than 3 x 10^{-37} cm^-2 produce a variation in the 8B neutrino fluxes that would be in conflict with current measurements.

Ilidio Lopes; Joseph Silk

2013-09-29T23:59:59.000Z

276

Environmentally Selected WIMP Dark Matter with High-Scale Supersymmetry Breaking  

E-Print Network (OSTI)

We explore the possibility that both the weak scale and the thermal relic dark matter abundance are environmentally selected in a multiverse. An underlying supersymmetric theory containing the states of the MSSM and singlets, with supersymmetry and R symmetry broken at unified scales, has just two realistic low energy effective theories. One theory, (SM + \\tilde{w}), is the Standard Model augmented only by the wino, having a mass near 3 TeV, and has a Higgs boson mass in the range of (127 - 142) GeV. The other theory, (SM + \\tilde{h}/\\tilde{s}), has Higgsinos and a singlino added to the Standard Model. The Higgs boson mass depends on the single new Yukawa coupling of the theory, y, and is near 141 GeV for small y but grows to be as large as 210 GeV as this new coupling approaches strong coupling at high energies. Much of the parameter space of this theory will be probed by direct detection searches for dark matter that push two orders of magnitude below the present bounds; furthermore, the dark matter mass and cross section on nucleons are correlated with the Higgs boson mass. The indirect detection signal of monochromatic photons from the galactic center is computed, and the range of parameters that may be accessible to LHC searches for trilepton events is explored. Taking a broader view, allowing the possibility of R symmetry protection to the TeV scale or axion dark matter, we find four more theories: (SM + axion), two versions of Split Supersymmetry, and the E-MSSM, where a little supersymmetric hierarchy is predicted. The special Higgs mass value of (141 \\pm 2) GeV appears in symmetry limits of three of the six theories, (SM + axion), (SM + \\tilde{w}) and (SM + \\tilde{h}/\\tilde{s}), motivating a comparison of other signals of these three theories.

Gilly Elor; Hock-Seng Goh; Lawrence J. Hall; Piyush Kumar; Yasunori Nomura

2009-12-19T23:59:59.000Z

277

Dynamics of Quintessence Models of Dark Energy with Exponential Coupling to the Dark Matter  

E-Print Network (OSTI)

We explore quintessence models of dark energy which exhibit non-minimal coupling between the dark matter and the dark energy components of the cosmic fluid. The kind of coupling chosen is inspired in scalar-tensor theories of gravity. We impose a suitable dynamics of the expansion allowing to derive exact Friedmann-Robertson-Walker solutions once the coupling function is given as input. Self-interaction potentials of single and double exponential types emerge as result of our choice of the coupling function. The stability and existence of the solutions is discussed in some detail. Although, in general, models with appropriated interaction between the components of the cosmic mixture are useful to handle the coincidence problem, in the present study the coincidence can not be evaded due to the choice of the solution generating ansatz.

Tame Gonzalez; Genly Leon; Israel Quiros

2007-02-08T23:59:59.000Z

278

End User Computing: The Dark Matter and Dark Energy of Corporate IT  

Science Conference Proceedings (OSTI)

End user computing EUC is like dark matter in physics. EUC is enormous in quantity and importance yet has been largely invisible to corporate IT departments, information systems IS researchers, and corporate management. EUC applications, especially spreadsheet ... Keywords: Base Error Rate, Cell Error Rate, Descriptive Research, End User Computing, Fourth Generation Languages 4GLs, Human Error, Mission-Critical, Primary Descriptive Research, Spreadsheet, Spreadsheet Error, Third Generation Languages 3GLs, Use And User Studies, User Studies

Raymond R. Panko, Daniel N. Port

2013-07-01T23:59:59.000Z

279

Gravitational Collapse With Dark Energy And Dark Matter In Ho?ava-Lifshitz Gravity  

E-Print Network (OSTI)

In this work, the collapsing process of a spherically symmetric star, made of dust cloud, is studied in Ho\\v{r}ava Lifshitz gravity in the background of Chaplygin gas dark energy. Two different classes of Chaplygin gas, namely, New variable modified Chaplygin gas and generalized cosmic Chaplygin gas are considered for the collapse study. Graphs are drawn to characterize the nature and to determine the possible outcome of gravitational collapse. A comparative study is done between the collapsing process in the two different dark energy models. It is found that for open and closed universe, collapse proceeds with an increase in black hole mass, the only constraint being that, relatively smaller values of $\\Lambda$ has to be considered in comparison to $\\lambda$. But in case of flat universe, possibility of the star undergoing a collapse in highly unlikely. Moreover it is seen that the most favourable environment for collapse is achieved when a combination of dark energy and dark matter is considered, both in the presence and absence of interaction. Finally, it is to be seen that, contrary to our expectations, the presence of dark energy does not really hinder the collapsing process in case of Ho\\v{r}ava-Lifshitz gravity.

Prabir Rudra; Ujjal Debnath

2013-07-12T23:59:59.000Z

280

Effect of dark matter annihilation on gas cooling and star formation  

E-Print Network (OSTI)

In the current paradigm of cosmic structure formation, dark matter plays a key role on the formation and evolution of galaxies through its gravitational influence. On microscopic scales, dark matter particles are expected to annihilate amongst themselves into different products, with some fraction of the energy being transferred to the baryonic component. It is the aim of the present work to show that, in the innermost regions of dark matter halos, heating by dark matter annihilation may be comparable to the cooling rate of the gas. We use analytical models of the dark matter and gas distributions in order to estimate the heating and cooling rates, as well as the energy available from supernova explosions. Depending on the model parameters and the precise nature of dark matter particles, the injected energy may be enough to balance radiative cooling in the cores of galaxy clusters. On galactic scales, it would inhibit star formation more efficiently than supernova feedback. Our results suggest that dark matte...

Ascasibar, Y

2006-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "dark matter searches" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


281

EVIDENCE FOR INDIRECT DETECTION OF DARK MATTER FROM GALAXY CLUSTERS IN FERMI {gamma}-RAY DATA  

SciTech Connect

Using the Fermi Large Area Telescope (LAT) we search for spectral features in {gamma}-rays coming from regions corresponding to the 18 brightest nearby galaxy clusters determined by the magnitude of their signal line-of-sight integrals. We observe a double-peak-like excess over the diffuse power-law background at photon energies of 110 GeV and 130 GeV with a global statistical significance of up to 3.6{sigma}, independently confirming earlier claims of the same excess from the Galactic center. Interpreting this result as a signal of dark matter annihilations to two monochromatic photon channels in galaxy cluster halos, and fixing the annihilation cross-section from the Galactic center data, we determine the annihilation boost factor due to dark matter subhalos from the data. Our results contribute to a discrimination of the dark matter annihilations from astrophysical processes and from systematic detector effects, offering them as possible explanations for the Fermi-LAT excess.

Hektor, A.; Raidal, M.; Tempel, E., E-mail: andi.hektor@cern.ch, E-mail: martti.raidal@cern.ch, E-mail: elmo@aai.ee [National Institute of Chemical Physics and Biophysics, Raevala 10, 10143 Tallinn(Estonia)

2013-01-10T23:59:59.000Z

282

Weak gravitational lensing as a method to constrain unstable dark matter  

SciTech Connect

The nature of the dark matter remains a mystery. The possibility of an unstable dark matter particle decaying to invisible daughter particles has been explored many times in the past few decades. Meanwhile, weak gravitational lensing shear has gained a lot of attention as a probe of dark energy, though it was previously considered a dark matter probe. Weak lensing is a useful tool for constraining the stability of the dark matter. In the coming decade a number of large galaxy imaging surveys will be undertaken and will measure the statistics of cosmological weak lensing with unprecedented precision. Weak lensing statistics are sensitive to unstable dark matter in at least two ways. Dark matter decays alter the matter power spectrum and change the angular diameter distance-redshift relation. We show how measurements of weak lensing shear correlations may provide the most restrictive, model-independent constraints on the lifetime of unstable dark matter. Our results rely on assumptions regarding nonlinear evolution of density fluctuations in scenarios of unstable dark matter and one of our aims is to stimulate interest in theoretical work on nonlinear structure growth in unstable dark matter models.

Wang Meiyu; Zentner, Andrew R. [Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 (United States)

2010-12-15T23:59:59.000Z

283

The orientation of galaxy dark matter haloes around cosmic voids  

E-Print Network (OSTI)

Using the Millennium N-body simulation we explore how the shape and angular momentum of galaxy dark matter haloes surrounding the largest cosmological voids are oriented. We find that the major and intermediate axes of the haloes tend to lie parallel to the surface of the voids, whereas the minor axis points preferentially in the radial direction. We have quantified the strength of these alignments at different radial distances from the void centres. The effect of these orientations is still detected at distances as large as 2.2 R_void from the void centre. Taking a subsample of haloes expected to contain disc-dominated galaxies at their centres we detect, at the 99.9% confidence level, a signal that the angular momentum of those haloes tends to lie parallel to the surface of the voids. Contrary to the alignments of the inertia axes, this signal is only detected in shells at the void surface (1dark matter haloes and baryonic matter have acquired, conjointly, their angular momentum before the moment of turnaround.

Riccardo Brunino; Ignacio Trujillo; Frazer R. Pearce; Peter A. Thomas

2006-09-22T23:59:59.000Z

284

Gamma-Ray Bursts and Dark Matter - a joint origin?  

E-Print Network (OSTI)

A scenario is presented where large quark-gluon plasma (QGP) objects escaping the quark-hadron transition in the early Universe account for the baryonic dark matter as well as act as the sources for gamma-ray bursts. Two basic assumptions are made. Firstly, we assume that a QGP consisting of u,d and s quarks is the absolute ground state of QCD and secondly, that the quark-hadron transition in the early Universe was of first order. Both particle physics and astrophysics constraints are discussed, mainly from an observational point of view.

Daniel Enstrom

1998-10-13T23:59:59.000Z

285

Superparticle Mass Window from Leptogenesis and Decaying Gravitino Dark Matter  

E-Print Network (OSTI)

Gravitino dark matter, together with thermal leptogenesis, implies an upper bound on the masses of superparticles. In the case of broken R-parity the constraints from primordial nucleosynthesis are naturally satisfied and decaying gravitinos lead to characteristic signatures in high energy cosmic rays. We analyse the implications for supergravity models with universal boundary conditions at the grand unification scale. Together with low-energy observables one obtains a window of superparticle masses, which will soon be probed at the LHC, and a range of allowed reheating temperatures.

Wilfried Buchmuller; Motoi Endo; Tetsuo Shindou

2008-09-26T23:59:59.000Z

286

Dark Matter Debris Flows in the Milky Way  

E-Print Network (OSTI)

We show that subhalos falling into the Milky Way create a flow of tidally-stripped debris particles near the galactic center with characteristic velocity behavior. In the Via Lactea-II N-body simulation, this unvirialized component constitutes a few percent of the local density and has velocities peaked at 340 km/s in the solar neighborhood. Such velocity substructure has important implications for surveys of low-metallicity stars, as well as direct detection experiments sensitive to dark matter with large scattering thresholds.

Mariangela Lisanti; David N. Spergel

2011-05-20T23:59:59.000Z

287

Strong Upper Limits on Sterile Neutrino Warm Dark Matter  

Science Conference Proceedings (OSTI)

Sterile neutrinos are attractive dark matter candidates. Their parameter space of mass and mixing angle has not yet been fully tested despite intensive efforts that exploit their gravitational clustering properties and radiative decays. We use the limits on gamma-ray line emission from the Galactic center region obtained with the SPI spectrometer on the INTEGRAL satellite to set new constraints, which improve on the earlier bounds on mixing by more than 2 orders of magnitude, and thus strongly restrict a wide and interesting range of models.

Yueksel, Hasan [Department of Physics, Ohio State University, Columbus, Ohio 43210 (United States); Center for Cosmology and Astro-Particle Physics, Ohio State University, Columbus, Ohio 43210 (United States); Beacom, John F. [Department of Physics, Ohio State University, Columbus, Ohio 43210 (United States); Center for Cosmology and Astro-Particle Physics, Ohio State University, Columbus, Ohio 43210 (United States); Department of Astronomy, Ohio State University, Columbus, Ohio 43210 (United States); Watson, Casey R. [Department of Physics and Astronomy, Millikin University, Decatur, Illinois 62522 (United States)

2008-09-19T23:59:59.000Z

288

A Hidden Valley model of cold dark matter  

E-Print Network (OSTI)

In the discussed model, the cold dark matter consists of Dirac spin-1/2 fermions, sterile from all Standard Model charges, where masses are generated by a nonzero vacuum expectation value of a field of scalar bosons, also assumed to be sterile. For convenience, these sterile particles have beeen called sterinos and sterons, respectively. It has been conjectured that our sterile world of sterinos and sterons can communicate with the familiar Standard Model world not only through gravity, but also through a photonic portal provided by a very weak effective interaction involving the electromagnetic field F_{\\mu \

Krolikowski, Wojciech

2008-01-01T23:59:59.000Z

289

Axionic Co-genesis of Baryon, Dark Matter and Dark Radiation  

E-Print Network (OSTI)

We argue that coherent oscillations of the axion field excited by the misalignment mechanism and non-thermal leptogenesis by the saxion decay can naturally explain the observed abundance of dark matter and baryon asymmetry, thus providing a solution to the baryon-dark matter coincidence problem. The successful axionic co-genesis requires a supersymmetry breaking scale of O(10^{6-7}) GeV, which is consistent with the recently discovered standard-model like Higgs boson of mass about 126 GeV. Although the saxion generically decays into a pair of axions, their abundance sensitively depends on the saxion stabilization mechanism as well as couplings with the Higgs field. We discuss various ways to make the saxion dominantly decay into the right-handed neutrinos rather than into axions, and show that the abundance of axion dark radiation can be naturally as small as \\Delta N_{\\rm eff} \\lesssim {\\cal O}(0.1), which is allowed by the Planck data.

Kwang Sik Jeong; Fuminobu Takahashi

2013-02-06T23:59:59.000Z

290

Trap with ultracold neutrons as a detector of dark matter with long-range forces  

SciTech Connect

The possibility of using a trap with ultracold neutrons (UCNs) as a detector of dark matter particles with long-range forces is considered. The main advantage of this method is the possibility of detecting recoil energies {approx}10{sup -7} eV. The limitations on the parameters of the interaction potential in the form {Psi}=ae{sup -r/b}/r between dark matter particles and neutrons at different values of the dark matter density on the Earth are represented. It is shown that the suggestion about the long-range character of the interaction between dark matter particles leads to a significant increase in the elastic scattering cross section at low energies. As a consequence, dark matter can be captured and accumulated by the terrestrial gravitational field. The first experimental limitations on the existence of long-range dark matter on the Earth are presented.

Serebrov, A. P., E-mail: serebrov@pnpi.spb.ru; Zherebtsov, O. M. [Russian Academy of Sciences, St. Petersburg Nuclear Physics Institute (Russian Federation)

2011-12-15T23:59:59.000Z

291

Neutralino dark matter in the left-right supersymmetric model  

SciTech Connect

We study the neutralino sector of the left-right supersymmetric model. In addition to the possibilities available in the minimal supersymmetric model, the neutralino states can be superpartners of the U(1){sub B-L} gauge boson, the neutral SU(2){sub R} gauge boson, or of the Higgs triplets. We analyze neutralino masses and determine the parameter regions for which the lightest neutralino can be one of the new pure states. We then calculate the relic density of the dark matter for each of these states and impose the constraints coming from the {rho} parameter, the anomalous magnetic moment of the muon, b{yields}s{gamma}, as well as general supersymmetric mass bounds. The lightest neutralino can be the bino, or the right-wino, or the neutral triplet Higgsino, all of which have different couplings to the standard model particles from the usual neutralinos. A light bino satisfies all the experimental constraints and would be the preferred dark matter candidate for light supersymmetric scalar masses, while the right-wino would be favored by intermediate supersymmetric mass scales. The neutral triplet Higgs fermion satisfies the experimental bounds only in a small region of the parameter space, for intermediate to heavy supersymmetric scalar masses.

Demir, Durmus A. [Department of Physics, Izmir Institute of Technology, IZTECH, TR35430, Izmir (Turkey); Frank, Mariana; Turan, Ismail [Department of Physics, Concordia University, 7141 Sherbrooke Street West, Montreal, Quebec, H4B 1R6 (Canada)

2006-06-01T23:59:59.000Z

292

A Dark-Matter Spike at the Galactic Center?  

E-Print Network (OSTI)

The past growth of the central black hole (BH) might have enhanced the density of cold dark matter halo particles at the Galactic center. We compute this effect in realistic growth models of the present (2-3)*10**6 solar mass BH from a low-mass seed BH, with special attention to dynamical modeling in a realistic galaxy environment with merger and orbital decay of a seed BH formed generally outside the exact center of the halo. An intriguing ``very-dense spike'' of dark matter has been claimed in models of Gondolo and Silk with density high enough to contradict with experimental upper bounds of neutralino annihilation radiation. This ``spike'' disappears completely or is greatly weakened when we include important dynamical processes neglected in their idealized/restrictive picture with cold particles surrounding an at-the-center zero-seed adiabaticly-growing BH. For the seed BH to spiral in and settle to the center within a Hubble time by dynamical friction, the seed mass must be at least a significant fraction of the present BH. Any subsequent at-the-center growth of the BH and steepening of the central Keplerian potential well can squeeze the halo density distribution only mildly, whether the squeezing happens adiabatically or instantaneously.

Piero Ullio; HongSheng Zhao; Marc Kamionkowski

2001-01-26T23:59:59.000Z

293

Dipole Moment Bounds on Scalar Dark Matter Annihilation  

E-Print Network (OSTI)

We consider a scalar dark matter annihilations to light leptons mediated by charged exotic fermions. The interaction of this model also adds a correction to dipole moments of light leptons. In the simplified model, these processes will depend upon the same coupling constants. The tight experimental bounds on the dipole moments of light leptons will constrain the coupling constants. Consequently, this bound will then limit the annihilations. We will produce this dipole moment bounds on the annihilation. From this analysis, we report that the bound on annihilation to the electrons is $4.0\\times10^{-7}\\pb$ (g-2) + $8.8\\times 10^{-15}\\pb$ (EDM) and the muons is $5.6\\times 10^{-4}\\pb$ (g-2) + $180\\pb$ (EDM), in the limit where the mediator is much heavier than dark matter. The parentheses indicate the dipole moment used to obtain the values. We note that only the annihilation to muons through a CP-violating (EDM) coupling is not excluded from indirect detection experiments.

Keita Fukushima

2013-10-07T23:59:59.000Z

294

The shapes, orientation, and alignment of Galactic dark matter subhalos  

E-Print Network (OSTI)

We present a study of the shapes, orientations, and alignments of Galactic dark matter subhalos in the ``Via Lactea'' simulation of a Milky Way-size LCDM host halo. Whereas isolated dark matter halos tend to be prolate, subhalos are predominantly triaxial. Overall subhalos are more spherical than the host halo, with minor to major and intermediate to major axis ratios of 0.68 and 0.83, respectively. Like isolated halos, subhalos tend to be less spherical in their central regions. The principal axis ratios are independent of subhalo mass, when the shapes are measured within a physical scale like r_Vmax, the radius of the peak of the circular velocity curve. Subhalos tend to be slightly more spherical closer to the host halo center. The spatial distribution of the subhalos traces the prolate shape of the host halo when they are selected by the largest V_max they ever had, i.e. before they experienced strong tidal mass loss. The subhalos' orientation is not random: the major axis tends to align with the direction towards the host halo center. This alignment disappears for halos beyond 3 r_200 and is more pronounced when the shapes are measured in the outer regions of the subhalos. The radial alignment is preserved during a subhalo's orbit and they become elongated during pericenter passage, indicating that the alignment is likely caused by the host halo's tidal forces. These tidal interactions with the host halo act to make subhalos rounder over time.

M. Kuhlen; J. Diemand; P. Madau

2007-05-14T23:59:59.000Z

295

Vector Higgs-portal dark matter and the invisible Higgs  

E-Print Network (OSTI)

The Higgs sector of the Standard Model offers a unique probe of the hidden sector. In this work, we explore the possibility of renormalizable Higgs couplings to the hidden sector vector fields which can constitute dark matter (DM). Abelian gauge sectors with minimal field content, necessary to render the gauge fields massive, have a natural Z_2 parity. This symmetry ensures stability of the vector fields making them viable dark matter candidates, while evading the usual electroweak constraints. We illustrate this idea with the Stueckelberg and Higgs mechanisms. Vector DM is consistent with the WMAP, XENON100, and LHC constraints, while it can affect significantly the invisible Higgs decay. Due to the enhanced branching ratio for the Higgs decay into the longitudinal components of the vector field, the vector Higgs portal provides an efficient way to hide the Higgs at the LHC. This could be the reason why the latest combined ATLAS/CMS data did not bring evidence for the existence of the Higgs boson.

Oleg Lebedev; Hyun Min Lee; Yann Mambrini

2011-11-18T23:59:59.000Z

296

Theory of superconductivity of gravitation and the dark matter enigma  

E-Print Network (OSTI)

In this article, the question of the nature of cold dark matter is approached from a new angle. By invoking the Cauchy problem of relativity it is shown how, under very precise astrophysical conditions, the Einstein general theory of relativity is formally equivalent to the Ginzburg-Landau theory of superconductivity. This fact lead us to suspect that the superconductivity of gravitation ought to be a real physical process occurring in the outskirts of galaxies. It is found that quantum mechanically gravity can achieve a type-II superconductor state characterised by the Gizburg-Landau parameter $\\kappa=1.5$, and it is suggested that a probability flux of Cooper pairs (quantum gravitational geons charged with vacuum energy) are directly responsible for the flatness exhibited by the rotation curves in spiral galaxies, as well as the exotic behaviour observed in galactic cluster collisions. If this hypothesis proves correct, the whole phenomenon of dark matter may count, after all, as another triumph for Einstein's theory of gravity. The tension between gravitation and quantum mechanics is explored further by a subtle consideration of the Hamilton-Jacobi theory of the York-time action, providing additional motivation for the above line of reasoning. In particular, Penrose's estimate for the rate of collapse of the wavefunction is recovered, and connected to the instability of Misner space.

Wenceslao Santiago-Germán

2011-12-06T23:59:59.000Z

297

Evolution of the First Stars with Dark Matter Burning  

E-Print Network (OSTI)

Recent theoretical studies have revealed the possibly important role of the capture and annihilation process of weakly interacting massive particles (WIMPs) for the first stars. Using new evolutionary models of metal-free massive stars, we investigate the impact of such ``dark matter burning'' for the first stars in different environments of dark matter (DM) halos, in terms of the ambient WIMP density (rho_chi). We find that, in agreement with existing literature, stellar life times can be significantly prolonged for a certain range of rho_\\chi (i.e., 10^{10} ~ 2*10^{11} GeV/cm3 may not undergo nuclear burning stages, confirming the previous work, and that ionizing photon fluxes from such DM supported stars are very weak. Delayed metal enrichment and slow reionization in the early universe would have resulted if most of the first stars had been born in DM halos with such high rho_\\chi, unless it had been lowered significantly below the threshold for efficient DM burning on a short time scale.

Sung-Chul Yoon; Fabio Iocco; Shizuka Akiyama

2008-06-17T23:59:59.000Z

298

The Small-Scale Power Spectrum of Cold Dark Matter  

E-Print Network (OSTI)

One of the best motivated hypotheses in cosmology states that most of the matter in the universe is in the form of weakly-interacting massive particles that decoupled early in the history of the universe and cooled adiabatically to an extremely low temperature. Nevertheless, the finite temperature and horizon scales at which these particles decoupled imprint generic signatures on their small scales density fluctuations. We show that the previously recognized cut-off in the fluctuation power-spectrum due to free-streaming of particles at the thermal speed of decoupling, is supplemented by acoustic oscillations owing to the initial coupling between the cold dark matter (CDM) and the radiation field. The power-spectrum oscillations appear on the scale of the horizon at thermal decoupling which corresponds to a mass scale of \\~10^{-4}*(T_d/10MeV)^{-3} solar masses for a CDM decoupling temperature T_d. The suppression of the power-spectrum on smaller scales by the acoustic oscillations is physically independent from the free-streaming effect, although the two cut-off scales are coincidentally comparable for T_d~10MeV and a particle mass of M~100GeV. The initial conditions for recent numerical simulations of the earliest and smallest objects to have formed in the universe, need to be modified accordingly. The smallest dark matter clumps may be detectable through gamma-ray production from particle annihilation, through fluctuations in the event rate of direct detection experiments, or through their tidal gravitational effect on wide orbits of objects near the outer edge of the solar system.

Abraham Loeb; Matias Zaldarriaga

2005-04-05T23:59:59.000Z

299

Annihilating dark matter and the galactic positron excess  

E-Print Network (OSTI)

The possibility that the Galactic dark matter is composed of neutralinos that are just above half the $Z^o$ mass is examined, in the context of the Galactic positron excess. In particular, we check if the anomalous bump in the cosmic ray positron to electron ratio at $10~GeV$ can be explained with the ``decay'' of virtual $Z^o$ bosons produced when the neutralinos annihilate. We find that the low energy behaviour of our prediction fits well the existing data. Assuming the neutralinos annihilate primarily in the distant density concentration in the Galaxy and allowing combination of older, diffused positrons with young free-streaming ones, produces a fit which is not satisfactory on its own but is significantly better than the one obtained with homogeneous injection.

Irit Maor

2006-02-20T23:59:59.000Z

300

Light-cone Simulations: Evolution of dark matter haloes  

E-Print Network (OSTI)

We present a new fast method for simulating pencil-beam type light-cones, using the MLAPM-code (Multi Level Adaptive Particle Mesh) with light-cone additions. We show that by a careful choice of the light-cone orientation, it is possible to avoid extra periodicities in the light-cone. As an example, we apply the method to simulate a 6 Gpc deep light-cone, create the dark matter halo catalogue for the light-cone and study the evolution of haloes from $z=6$ up to the present time. We determine the spatial density of the haloes, their large-scale correlation function, and study the evolution of the mass function. We find a surprisingly simple relation for the dependence of halo maximum mass on redshift, and apply it to derive redshift limits for bright quasars.

P. Hein"am"aki; I. Suhhonenko; E. Saar; Maret Einasto; Jaan Einasto; Heidi Virtanen

2005-07-08T23:59:59.000Z

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301

Solar Gamma Rays Powered by Secluded Dark Matter  

E-Print Network (OSTI)

Secluded dark matter models, in which WIMPs annihilate first into metastable mediators, can present novel indirect detection signatures in the form of gamma rays and fluxes of charged particles arriving from directions correlated with the centers of large astrophysical bodies within the solar system, such as the Sun and larger planets. This naturally occurs if the mean free path of the mediator is in excess of the solar (or planetary) radius. We show that existing constraints from water Cerenkov detectors already provide a novel probe of the parameter space of these models, complementary to other sources, with significant scope for future improvement from high angular resolution gamma-ray telescopes such as Fermi-LAT. Fluxes of charged particles produced in mediator decays are also capable of contributing a significant solar system component to the spectrum of energetic electrons and positrons, a possibility which can be tested with the directional and timing information of PAMELA and Fermi.

Brian Batell; Maxim Pospelov; Adam Ritz; Yanwen Shang

2009-10-08T23:59:59.000Z

302

Solar gamma rays powered by secluded dark matter  

Science Conference Proceedings (OSTI)

Secluded dark matter models, in which weakly interacting massive particles annihilate first into metastable mediators, can present novel indirect detection signatures in the form of gamma rays and fluxes of charged particles arriving from directions correlated with the centers of large astrophysical bodies within the Solar System, such as the Sun and larger planets. This naturally occurs if the mean free path of the mediator is in excess of the solar (or planetary) radius. We show that existing constraints from water Cerenkov detectors already provide a novel probe of the parameter space of these models, complementary to other sources, with significant scope for future improvement from high angular resolution gamma-ray telescopes such as Fermi-LAT. Fluxes of charged particles produced in mediator decays are also capable of contributing a significant solar system component to the spectrum of energetic electrons and positrons, a possibility which can be tested with the directional and timing information of PAMELA and Fermi.

Batell, Brian; Shang Yanwen [Perimeter Institute for Theoretical Physics, Waterloo, Ontario, N2J 2W9 (Canada); Pospelov, Maxim [Perimeter Institute for Theoretical Physics, Waterloo, Ontario, N2J 2W9 (Canada); Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia, V8P 1A1 (Canada); Ritz, Adam [Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia, V8P 1A1 (Canada)

2010-04-01T23:59:59.000Z

303

TeV scale dark matter and electroweak radiative corrections  

SciTech Connect

Recent anomalies in cosmic rays data, namely, from the PAMELA Collaboration, can be interpreted in terms of TeV scale decaying/annihilating dark matter. We analyze the impact of radiative corrections coming from the electroweak sector of the standard model on the spectrum of the final products at the interaction point. As an example, we consider virtual one loop corrections and real gauge bosons emission in the case of a very heavy vector boson annihilating into fermions. We find electroweak corrections that are relevant, but not as big as sometimes found in the literature; we relate this mismatch to the issue of gauge invariance. At scales much higher than the symmetry breaking scale, one loop electroweak effects are so big that eventually higher orders/resummations have to be considered: we advocate for the inclusion of these effects in parton shower Monte Carlo models aiming at the description of TeV scale physics.

Ciafaloni, Paolo; Urbano, Alfredo [INFN - Sezione di Lecce and Universita del Salento, Via per Arnesano, I-73100 Lecce (Italy)

2010-08-15T23:59:59.000Z

304

A model for a non-minimally coupled scalar field interacting with dark matter  

E-Print Network (OSTI)

In this work we investigate the evolution of a Universe consisted of a scalar field, a dark matter field and non-interacting baryonic matter and radiation. The scalar field, which plays the role of dark energy, is non-minimally coupled to space-time curvature, and drives the Universe to a present accelerated expansion. The non-relativistic dark matter field interacts directly with the dark energy and has a pressure which follows from a thermodynamic theory. We show that this model can reproduce the expected behavior of the density parameters, deceleration parameter and luminosity distance.

J. B. Binder; G. M. Kremer

2006-01-25T23:59:59.000Z

305

Dark matter limits froma 15 kg windowless bubble chamber  

SciTech Connect

The COUPP collaboration has successfully used bubble chambers, a technology previously applied only to high-energy physics experiments, as direct dark matter detectors. It has produced the world's most stringent spin-dependent WIMP limits, and increasingly competitive spin-independent limits. These limits were achieved by capitalizing on an intrinsic rejection of the gamma background that all other direct detection experiments must address through high-density shielding and empirically-determined data cuts. The history of COUPP, including its earliest prototypes and latest results, is briefly discussed in this thesis. The feasibility of a new, windowless bubble chamber concept simpler and more inexpensive in design is discussed here as well. The dark matter limits achieved with a 15 kg windowless chamber, larger than any previous COUPP chamber (2 kg, 4 kg), are presented. Evidence of the greater radiopurity of synthetic quartz compared to natural is presented using the data from this 15 kg device, the first chamber to be made from synthetic quartz. The effective reconstruction of the three-dimensional positions of bubbles in a highly distorted optical field, with ninety-degree bottom lighting similar to cloud chamber lighting, is demonstrated. Another innovation described in this thesis is the use of the sound produced by bubbles recorded by an array of piezoelectric sensors as the primary means of bubble detection. In other COUPP chambers, cameras have been used as the primary trigger. Previous work on bubble acoustic signature differentiation using piezos is built upon in order to further demonstrate the ability to discriminate between alpha- and neutron-induced events.

Szydagis, Matthew Mark; /Chicago U.

2010-12-01T23:59:59.000Z

306

WEAKLY INTERACTING MASSIVE PARTICLE DARK MATTER AND FIRST STARS: SUPPRESSION OF FRAGMENTATION IN PRIMORDIAL STAR FORMATION  

SciTech Connect

We present the first three-dimensional simulations to include the effects of dark matter annihilation feedback during the collapse of primordial minihalos. We begin our simulations from cosmological initial conditions and account for dark matter annihilation in our treatment of the chemical and thermal evolution of the gas. The dark matter is modeled using an analytical density profile that responds to changes in the peak gas density. We find that the gas can collapse to high densities despite the additional energy input from the dark matter. No objects supported purely by dark matter annihilation heating are formed in our simulations. However, we find that dark matter annihilation heating has a large effect on the evolution of the gas following the formation of the first protostar. Previous simulations without dark matter annihilation found that protostellar disks around Population III stars rapidly fragmented, forming multiple protostars that underwent mergers or ejections. When dark matter annihilation is included, however, these disks become stable to radii of 1000 AU or more. In the cases where fragmentation does occur, it is a wide binary that is formed.

Smith, Rowan J.; Glover, Simon C. O.; Klessen, Ralf S. [Institut fuer Theoretische Astrophysik, Zentrum fuer Astronomie, Universitaet Heidelberg, Albert-Ueberle-Str. 2, D-69120 Heidelberg (Germany); Iocco, Fabio [Department of Physics, Oskar Klein Centre, AlbaNova, Stockholm University, SE-106 91 Stockholm (Sweden); Schleicher, Dominik R. G. [Institut fuer Astrophysik, Georg-August-Universitaet, Friedrich-Hund-Platz 1, D-37077 Goettingen (Germany); Hirano, Shingo; Yoshida, Naoki, E-mail: rowan@uni-heidelberg.de [Kavli Institute for the Physics and Mathematics of the Universe, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8568 (Japan)

2012-12-20T23:59:59.000Z

307

Energy from the Center of the Milky Way May Be the Remnant of Dark Matter |  

Office of Science (SC) Website

Energy from Energy from the Center of the Milky Way May Be the Remnant of Dark Matter News Featured Articles 2014 2013 2012 2011 2010 2009 2008 2007 2006 2005 Science Headlines Presentations & Testimony News Archives Contact Information Office of Science U.S. Department of Energy 1000 Independence Ave., SW Washington, DC 20585 P: (202) 586-5430 11.17.10 Energy from the Center of the Milky Way May Be the Remnant of Dark Matter Dark matter particles continue to hide, but they release energy when they collide: evidence shows that gamma rays from the center of our galaxy may come from dark matter collisions. Print Text Size: A A A Subscribe FeedbackShare Page From the center of the Milky Way, dark matter particles may be sending signals of their existence. Astrophysicists analyzing data from the center

308

Bounds on self-interacting fermion dark matter from observations of old neutron stars  

E-Print Network (OSTI)

The existence of old neutron stars deeply constrains self-interacting fermion dark matter, which can form star-killing black holes. We quantify this constraint on dark matter-nucleon scattering, considering collapse scenarios that broaden bounds over intermediate masses. We then find the self- and co-annihilation rates necessary to lift these dark matter-nucleon scattering bounds. For Yukawa-coupled dark matter that fits dwarf galaxy halo profiles with a coupling $\\alpha = 10^{-1}-10^{-4}$, a scalar mediator mass $m_\\phi = 1-500$ MeV, and DM mass $m_X = 0.1-10^7$ GeV, we show that fermion dark matter is unconstrained if it self-annihilates at a rate greater than $10^{-40} ~ \\rm{cm^3/s}$ or co-annihilates with baryons at a rate greater than $10^{-50} ~ \\rm{cm^3/s}$.

Joseph Bramante; Keita Fukushima; Jason Kumar; Elan Stopnitzky

2013-10-13T23:59:59.000Z

309

On the Oscillation of Neutrinos Produced by the Annihilation of Dark Matter inside the Sun  

E-Print Network (OSTI)

The annihilation of dark matter particles captured by the Sun can lead to a neutrino flux observable in neutrino detectors. Considering the fact that these dark matter particles are non-relativistic, if a pair of dark matter annihilates to a neutrino pair, the spectrum of neutrinos will be monochromatic. We show that in this case, even after averaging over production point inside the Sun, the oscillatory terms of the oscillation probability do not average to zero. This leads to interesting observable features in the annual variation of the number of muon track events. We show that smearing of the spectrum due to thermal distribution of dark matter inside the Sun is too small to wash out this variation. We point out the possibility of studying the initial flavor composition of neutrinos produced by the annihilation of dark matter particles via measuring the annual variation of the number of muon-track events in neutrino telescopes.

Arman Esmaili; Yasaman Farzan

2009-12-20T23:59:59.000Z

310

arXiv:astro-ph/0208093v327Nov2002 Dark Energy and Matter Evolution from Lensing Tomography  

E-Print Network (OSTI)

arXiv:astro-ph/0208093v327Nov2002 Dark Energy and Matter Evolution from Lensing Tomography Wayne Hu on the growth function of structure and the evolution of the dark energy density. We examine this potential tests for the existence of multiple dark matter components or a dark energy component

Hu, Wayne

311

Shedding Light on Dark Matter and Dark Energy | Argonne National Laboratory  

NLE Websites -- All DOE Office Websites (Extended Search)

Fig. 2: Time evolution of structure formation. A zoom-in to an approximately 70-Mpc-wide region is shown. The frames depict the structure at different redshifts or temporal epochs. Comparison to the overall box size of 9.14 Gpc in linear dimension shows the impressive dynamic range achievable on the BG/Q. Fig. 2: Time evolution of structure formation. A zoom-in to an approximately 70-Mpc-wide region is shown. The frames depict the structure at different redshifts or temporal epochs. Comparison to the overall box size of 9.14 Gpc in linear dimension shows the impressive dynamic range achievable on the BG/Q. Fig. 2: Time evolution of structure formation. A zoom-in to an approximately 70-Mpc-wide region is shown. The frames depict the structure at different redshifts or temporal epochs. Comparison to the overall box size of 9.14 Gpc in linear dimension shows the impressive dynamic range achievable on the BG/Q. Shedding Light on Dark Matter and Dark Energy By Gail Pieper * March 6, 2013 Tweet EmailPrint Cosmology is currently in one of its most scientifically exciting phases.

312

Development of the Liquid Level Meters for the PandaX Dark Matter Detector  

E-Print Network (OSTI)

The two-phase xenon detector is at the frontier of dark matter direct search. This kind of detector uses liquid xenon as the sensitive target and is operated in two-phase (liquid/gas) mode, where the liquid level needs to be monitored and controlled in sub-millimeter precision. In this paper, we present a detailed design and study of two kinds of level meters for the PandaX dark matter detector. The long level meter is used to monitor the overall liquid level while short level meters are used to monitor the inclination of the detector. These level meters are cylindrical capacitors custom-made from two concentric metal tubes. Their capacitance values are read out by a universal transducer interface chip and recorded by the PandaX slow control system. We present the developments that lead to level meters with long-term stability and sub-millimeter precision. Fluctuations (standard deviations) of less than 0.02 mm for the short level meters and less than 0.2 mm for the long level meter were achieved during a few days of test operation.

J. Hu; H. Gong; Q. Lin; K. Ni; A. Tan; Y. Wei; M. Xiao; X. Xiao; L. Zhao

2013-06-13T23:59:59.000Z

313

Hidden sector dark matters and elusive Higgs boson(s) at the LHC  

Science Conference Proceedings (OSTI)

We consider two types of hidden sector dark matters (DM's), with and without QCD-like new strong interaction with confinement properties, and their interplays with the Standard Model (SM) Higgs boson. Assuming the hidden sector has only fermions (and gauge bosons in case of strongly interacting hidden sector), we have to introduce a real singlet scalar boson S as a messenger between the SM and the hidden sector dark matters. This singlet scalar will mix with the SM Higgs boson h, and we expect there are two Higgs-like scalar bosons H{sub 1} and H{sub 2}. Imposing all the relevant constraints from collider search bounds on Higgs boson, DM scattering cross section on proton and thermal relic density, we find that one of the two Higgs-like scalar bosons can easily escape the detections at the LHC. Recent results on the Higgs-like new boson with mass around with 125 GeV from the LHC will constrain this class of models, which is left for future study.

Ko, P. [School of Physics, KIAS, Seoul 130-722 (Korea, Republic of)

2012-07-27T23:59:59.000Z

314

Development of the Liquid Level Meters for the PandaX Dark Matter Detector  

E-Print Network (OSTI)

The two-phase xenon detector is at the frontier of dark matter direct search. This kind of detector uses liquid xenon as the sensitive target and is operated in two-phase (liquid/gas) mode, where the liquid level needs to be monitored and controlled in sub-millimeter precision. In this paper, we present a detailed design and study of two kinds of level meters for the PandaX dark matter detector. The long level meter is used to monitor the overall liquid level while short level meters are used to monitor the inclination of the detector. These level meters are cylindrical capacitors custom-made from two concentric metal tubes. Their capacitance values are read out by a universal transducer interface chip and recorded by the PandaX slow control system. We present the developments that lead to level meters with long-term stability and sub-millimeter precision. Fluctuations (standard deviations) of less than 0.02 mm for the short level meters and less than 0.2 mm for the long level meter were achieved during a few...

Hu, J; Lin, Q; Ni, K; Tan, A; Wei, Y; Xiao, M; Xiao, X; Zhao, L

2013-01-01T23:59:59.000Z

315

Presentation of the Second Big Challenge Symposium - The Big Challenge of Cosmological Understanding: Gravitation, Dark Matter and Dark Energy. Towards New Scenarios  

E-Print Network (OSTI)

This Symposium is devoted to the Memory of Lev Kofman, June-17-1957-November-12-2009. The accelerated expansion of the Universe, which is today observed, shows that cosmological dynamics is dominated by the so-called Dark Energy field which provides a large negative pressure. This is the standard picture, in which such new ingredient is considered as a source of the right hand side of the field equations. It should be some form of non-clustered non-zero vacuum energy which, together with the clustered Dark Matter, drives the global dynamics. This is the so-called "concordance model" (ACDM) which gives, in agreement with the Cosmic Microwave Background Radiation (CMBR), dim Lyman Limit Systems (LLS) and type la supernovae (SNeIa) data, a good framework to understand the today observed Universe. However, it presents several shortcomings as the well known "coincidence" and "cosmological constant" problems . An alternative approach is to have a better understanding of the energy concept in General Relativity and also to change the left hand side of the field equations, and check if observed cosmic dynamics can be achieved by extending general relativity. In this different context, it is not required to search candidates for Dark Energy and Dark Matter, which till now have not been found. Rather, one can only stand on the "observed" ingredients: curvature and baryon matter, to account for the observations. Considering this point of view, one can think of that gravity is not scale-invariant. The goal of this Symposium is to obtain a tapestry of the present status of theory and observations concerning Gravitation and Dark Universe.

Christian Corda

2010-07-23T23:59:59.000Z

316

Effect of dark matter annihilation on gas cooling and star formation  

E-Print Network (OSTI)

In the current paradigm of cosmic structure formation, dark matter plays a key role on the formation and evolution of galaxies through its gravitational influence. On microscopic scales, dark matter particles are expected to annihilate amongst themselves into different products, with some fraction of the energy being transferred to the baryonic component. It is the aim of the present work to show that, in the innermost regions of dark matter halos, heating by dark matter annihilation may be comparable to the cooling rate of the gas. We use analytical models of the dark matter and gas distributions in order to estimate the heating and cooling rates, as well as the energy available from supernova explosions. Depending on the model parameters and the precise nature of dark matter particles, the injected energy may be enough to balance radiative cooling in the cores of galaxy clusters. On galactic scales, it would inhibit star formation more efficiently than supernova feedback. Our results suggest that dark matter annihilation prevents gas cooling and star formation within at least $0.01-1$ per cent of the virial radius.

Y. Ascasibar

2006-12-05T23:59:59.000Z

317

Cogeneration of Dark Matter and Baryons by Non-Standard-Model Sphalerons in Unified Models  

E-Print Network (OSTI)

Sphalerons of a new gauge interaction can convert a primordial asymmetry in B or L into a dark matter asymmetry. From the equilibrium conditions for the sphalerons of both the electroweak and the new interactions, one can compute the ratios of B, L, and X, where X is the dark matter number, thus determining the mass of the dark matter particle fairly precisely. Such a scenario can arise naturally in the context of unification with larger groups. An illustrative model embeddable in $SU(6) \\times SU(2) \\subset E_6$ is described as well as an equally simple model based on SU(7).

S. M. Barr; Heng-Yu Chen

2013-08-30T23:59:59.000Z

318

Cogeneration of Dark Matter and Baryons by Non-Standard-Model Sphalerons  

E-Print Network (OSTI)

Sphalerons of a new gauge interaction can convert a primordial asymmetry in B or L into a dark matter asymmetry. From the equilibrium conditions for the sphalerons of both the electroweak and the new interactions, one can compute the ratios of B, L, and X, where X is the dark matter number, thus determining the mass of the dark matter particle fairly precisely. Such a scenario can arise naturally in the context of unification with larger groups. An illustrative model embeddable in $SU(6) \\times SU(2) \\subset E_6$ is described.

Barr, S M

2013-01-01T23:59:59.000Z

319

HALO-TO-HALO SIMILARITY AND SCATTER IN THE VELOCITY DISTRIBUTION OF DARK MATTER  

SciTech Connect

We examine the velocity distribution function (VDF) in dark matter halos from Milky Way to cluster mass scales. We identify an empirical model for the VDF with a wider peak and a steeper tail than a Maxwell-Boltzmann distribution, and discuss physical explanations. We quantify sources of scatter in the VDF of cosmological halos and their implication for direct detection of dark matter. Given modern simulations and observations, we find that the most significant uncertainty in the VDF of the Milky Way arises from the unknown radial position of the solar system relative to the dark matter halo scale radius.

Mao, Yao-Yuan; Strigari, Louis E.; Wechsler, Risa H.; Hahn, Oliver [Kavli Institute for Particle Astrophysics and Cosmology and Physics Department, Stanford University, Stanford, CA 94305, USAAND (United States) [Kavli Institute for Particle Astrophysics and Cosmology and Physics Department, Stanford University, Stanford, CA 94305, USAAND (United States); SLAC National Accelerator Laboratory, Menlo Park, CA 94025 (United States); Wu, Hao-Yi [Currently at Physics Department, The University of Michigan, Ann Arbor, MI 48109, USA. (United States)] [Currently at Physics Department, The University of Michigan, Ann Arbor, MI 48109, USA. (United States)

2013-02-10T23:59:59.000Z

320

Dark matter haloes determine the masses of supermassive black holes  

E-Print Network (OSTI)

The energy and momentum deposited by the radiation from accretion onto the supermassive black holes (BHs) that reside at the centres of virtually all galaxies can halt or even reverse gas inflow, providing a natural mechanism for supermassive BHs to regulate their growth and to couple their properties to those of their host galaxies. However, it remains unclear whether this self-regulation occurs on the scale at which the BH is gravitationally dominant, on that of the stellar bulge, the galaxy, or that of the entire dark matter halo. To answer this question, we use self-consistent simulations of the co-evolution of the BH and galaxy populations that reproduce the observed correlations between the masses of the BHs and the properties of their host galaxies. We first confirm unambiguously that the BHs regulate their growth: the amount of energy that the BHs inject into their surroundings remains unchanged when the fraction of the accreted rest mass energy that is injected, is varied by four orders of magnitude....

Booth, C M

2009-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "dark matter searches" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
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321

MAPPING THE DARK MATTER WITH POLARIZED RADIO SURVEYS  

Science Conference Proceedings (OSTI)

In a recent paper, we proposed the use of integrated polarization measurements of background galaxies in radio weak gravitational lensing surveys and investigated the potential impact on the statistical measurement of cosmic shear. Here we extend this idea to reconstruct maps of the projected dark matter distribution or lensing convergence field. The addition of polarization can, in principle, greatly reduce shape noise due to the intrinsic dispersion in galaxy ellipticities. We show that maps reconstructed using this technique in the radio band can be competitive with those derived using standard lensing techniques which make use of many more galaxies. In addition, since the reconstruction noise is uncorrelated between these standard techniques and the polarization technique, their comparison can serve as a powerful check for systematics and their combination can reduce noise further. We examine the convergence reconstruction which could be achieved with two forthcoming facilities: (1) a deep survey, covering 1.75 deg{sup 2} using the e-MERLIN instrument currently being commissioned in the UK and (2) the high-resolution, deep wide-field surveys which will eventually be conducted with the Square Kilometre Array.

Brown, Michael L. [Astrophysics Group, Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge CB3 OHE (United Kingdom); Battye, Richard A. [Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL (United Kingdom)

2011-07-01T23:59:59.000Z

322

Background studies for a ton-scale argon dark matter detector (ArDM)  

E-Print Network (OSTI)

The ArDM project aims at operating a large noble liquid detector to search for direct evidence of Weakly Interacting Massive Particles (WIMP) as Dark Matter in the universe. Background sources relevant to ton-scale liquid and gaseous argon detectors, such as neutrons from detector components, muon-induced neutrons and neutrons caused by radioactivity of rock, as well as the internal $^{39}Ar$ background, are studied with simulations. These background radiations are addressed with the design of an appropriate shielding as well as with different background rejection potentialities. Among them the project relies on event topology recognition, event localization, density ionization discrimination and pulse shape discrimination. Background rates, energy spectra, characteristics of the background-induced nuclear recoils in liquid argon, as well as the shielding performance and rejection performance of the detector are described.

L. Kaufmann; A. Rubbia

2006-12-05T23:59:59.000Z

323

At the heart of the matter: the origin of bulgeless dwarf galaxies and Dark Matter cores  

E-Print Network (OSTI)

For almost two decades the properties of "dwarf" galaxies have challenged the Cold Dark Matter (CDM) paradigm of galaxy formation. Most observed dwarf galaxies consists of a rotating stellar disc embedded in a massive DM halo with a near constant-density core. Yet, models based on the CDM scenario invariably form galaxies with dense spheroidal stellar "bulges" and steep central DM profiles, as low angular momentum baryons and DM sink to the center of galaxies through accretion and repeated mergers. Processes that decrease the central density of CDM halos have been identified, but have not yet reconciled theory with observations of present day dwarfs. This failure is potentially catastrophic for the CDM model, possibly requiring a different DM particle candidate. This Letter presents new hydrodynamical simulations in a Lambda$CDM framework where analogues of dwarf galaxies, bulgeless and with a shallow central DM profile, are formed. This is achieved by resolving the inhomogeneous interstellar medium, resulting in strong outflows from supernovae explosions which remove low angular momentum gas. This inhibits the formation of bulges and decreases the dark-matter density to less than half within the central kiloparsec. Realistic dwarf galaxies are thus shown to be a natural outcome of galaxy formation in the CDM scenario.

Fabio Governato; Chris Brook; Lucio Mayer; Alyson Brooks; George Rhee; James Wadsley; Patrik Jonsson; Beth Willman; Greg Stinson; Thomas Quinn; Piero Madau

2009-11-11T23:59:59.000Z

324

Comprehensive Constraints on a Spin-3/2 Singlet Particle as a Dark Matter Candidate  

E-Print Network (OSTI)

We consider the proposal that dark matter (DM) is composed of a spin-3/2 particle that is a singlet of the standard model (SM). Its leading effective interactions with ordinary matter involve a pair of their fields and a pair of SM fermions, in the form of products of chiral currents. We make a comprehensive analysis on possible phenomenological effects of the interactions in various experiments and observations. These include collider searches for monojet plus missing transverse energy events, direct detections of DM scattering off nuclei, possible impacts on the gamma rays and antiproton-to-proton flux ratio in cosmic rays, and the observed relic density. The current data already set strong constraints on the effective interactions in a complementary manner. The constraint from collider searches is most effective at a relatively low mass of DM, and the antiproton-to-proton flux ratio offers the best bound for a heavy DM, while the spin-independent direct detection is the best in between. For DM mass of order 10 GeV to 1 TeV, the effective interaction scale is constrained to be typically above a few tens TeV.

Ran Ding; Yi Liao; Ji-Yuan Liu; Kai Wang

2013-02-17T23:59:59.000Z

325

Dark matter: the next great discovery of particle physics?: Ettore Majorana through the Looking-glass  

SciTech Connect

As we celebrate the completion of the Standard Model with the discovery of a Higgs-like boson, some of us are working hard on what may be the next great discovery of particle physics. The problem of missing mass, which is now known as dark matter, has persisted for nearly a century. In this time, astrophysical evidence in favor of dark matter has only grown stronger. We now know that dark matter constitutes a majority of the matter in the Universe, yet it is not composed of any particle in the Standard Model. Dark matter is necessary for the formation of galaxies and galaxy clusters and hence has shaped the Universe as we know it. Despite this body of knowledge, we still don't know what particles compose dark matter or how they interact with the particles of the Standard Model. The answers to these remaining questions are being pursued on all frontiers of discovery. In this talk, I will provide an overview of the suite of experiments that is colloquially known as "direct detection" experiments. I will describe how these experiments aim to solve the dark matter puzzle, highlight some of the most promising efforts and conclude with a discussion on future prospects.

Hsu, Lauren [Fermilab

2012-10-31T23:59:59.000Z

326

Designing and testing the neutron source deployment system and calibration plan for a dark matter detector  

E-Print Network (OSTI)

In this thesis, we designed and tested a calibration and deployment system for the MiniCLEAN dark matter detector. The deployment system uses a computer controlled winch to lower a canister containing a neutron source into ...

Westerdale, Shawn (Shawn S.)

2011-01-01T23:59:59.000Z

327

High Energy Electron Signals from Dark Matter Annihilation in the Sun  

Science Conference Proceedings (OSTI)

In this paper we discuss two mechanisms by which high energy electrons resulting from dark matter annihilations in or near the Sun can arrive at the Earth. Specifically, electrons can escape the sun if DM annihilates into long-lived states, or if dark matter scatters inelastically, which would leave a halo of dark matter outside of the sun. Such a localized source of electrons may affect the spectra observed by experiments with narrower fields of view oriented towards the sun, such as ATIC, differently from those with larger fields of view such as Fermi. We suggest a simple test of these possibilities with existing Fermi data that is more sensitive than limits from final state radiation. If observed, such a signal will constitute an unequivocal signature of dark matter.

Schuster, Philip; /SLAC; Toro, Natalia; /Stanford U., ITP; Weiner, Neal; Yavin, Itay; /New York U., CCPP

2012-04-09T23:59:59.000Z

328

Scalar dark matter and fermion coannihilations in the radiative seesaw model  

E-Print Network (OSTI)

By extending the Standard Model with three right-handed neutrinos (N_i) and a second Higgs doublet (H_2), odd under a Z_2 symmetry, it is possible to explain non-zero neutrino masses and to account for the dark matter. We consider the case where the dark matter is a scalar and study its coannihilations with the right-handed neutrinos. These coannihilations tend to increase, rather than reduce, the dark matter density and they modify in a significant way the viable parameter space of the model. In particular, they allow to satisfy the relic density constraint for dark matter masses well below 500 GeV. The dependence of the relic density on the relevant parameters of the model, such as the dark matter mass, the mass splitting, and the number of coannihilating fermions, is analyzed in detail. We also investigate, via a scan over the parameter space, the new viable regions that are obtained when coannihilations are taken into account. Notably, they feature large indirect detection rates, with sigmav reaching values of order 10^{-24} cm^3/s. Finally, we emphasize that coannihilation effects analogous to those discussed here can be used to reconcile a thermal freeze-out with a large sigmav also in other models of dark matter.

Michael Klasen; Carlos E. Yaguna; Jose D. Ruiz-Alvarez; Diego Restrepo; Oscar Zapata

2013-02-21T23:59:59.000Z

329

DIURNAL AND ANNUAL VARIATIONS OF DIRECTIONAL DETECTION RATES OF DARK MATTER  

Science Conference Proceedings (OSTI)

Direction-sensitive direct detection of weakly interacting massive particles (WIMPs) as dark matter would provide an unambiguous non-gravitational signature of dark matter. The diurnal variation of dark matter signal due to Earth's rotation around its own axis can be a significant signature for Galactic WIMPs. Because of a particular orientation of Earth's axis of rotation with respect to the WIMP wind direction, the apparent direction of WIMP wind as observed at a detector can alter widely in a day. In this work, we calculate the directional detection rates with their daily and yearly modulations in Earth-bound dark matter experiments considering detailed features of the geometry and dynamics of the Earth-Sun system along with the solar motion in a Galactic frame. A separate halo model, namely the dark disk model other than the usual standard halo model for dark matter halo, is also considered and the results for two models are compared. We demonstrate the results for two types of gas detectors, namely DRIFT (target material CS{sub 2}) and NEWAGE (target material CF{sub 4}), which use Time Projection Chamber techniques for measuring directionality of the recoil nucleus. The WIMP mass and recoil energy dependence of the daily variation of event rates are computed for a specific detector, and the sensitive ranges of mass and recoil energies for the considered detector are probed.

Bandyopadhyay, Abhijit [Department of Physics, RKM Vivekananda University, Belur Math, Howrah 711202 (India); Majumdar, Debasish, E-mail: abhi.vu@gmail.com, E-mail: debasish.majumdar@saha.ac.in [Astroparticle Physics and Cosmology Division, Saha Institute of Nuclear Physics, Kolkata 700064 (India)

2012-02-10T23:59:59.000Z

330

Problems of antimatter after Big Bang, dark energy and dark matter. Solutions in the frame of non-local physics  

E-Print Network (OSTI)

Quantum solitons are discovered with the help of generalized quantum hydrodynamics. The solitons have the character of the stable quantum objects in the self consistent electric field. The delivered theory demonstrates the great possibilities of the generalized quantum hydrodynamics in investigation of the quantum solitons. The theory leads to solitons as typical formations in the generalized quantum hydrodynamics. The principle of universal antigravitation is considered from positions of the Newtonian theory of gravitation and non-local kinetic theory. It is found that explanation of Hubble effect in the Universe and peculiar features of the rotational speeds of galaxies need not in introduction of new essence like dark matter and dark energy. Problems of antimatter after Big Bang are considered from positions of non-local physics. The origin of difficulties consists in total Oversimplification following from principles of local physics and reflects the general shortenings of the local kinetic transport theory. Keywords: Foundations of the theory of transport processes; generalized Boltzmann physical kinetics; plasma - gravitational analogy; antigravitation; dark energy; dark matter; the theory of solitons; antimatter after Big Bang. PACS: 67.55.Fa, 67.55.Hc

Boris V. Alexeev

2010-12-22T23:59:59.000Z

331

THE CONNECTION BETWEEN GALAXIES AND DARK MATTER STRUCTURES IN THE LOCAL UNIVERSE  

SciTech Connect

We provide new constraints on the connection between galaxies in the local universe, identified by the Sloan Digital Sky Survey, and dark matter halos and their constituent substructures in the {Lambda}-cold dark matter model using WMAP7 cosmological parameters. Predictions for the abundance and clustering properties of dark matter halos, and the relationship between dark matter hosts and substructures, are based on a high-resolution cosmological simulation, the Bolshoi simulation. We associate galaxies with dark matter halos and subhalos using subhalo abundance matching, and perform a comprehensive analysis which investigates the underlying assumptions of this technique including (1) which halo property is most closely associated with galaxy stellar masses and luminosities, (2) how much scatter is in this relationship, and (3) how much subhalos can be stripped before their galaxies are destroyed. The models are jointly constrained by new measurements of the projected two-point galaxy clustering and the observed conditional stellar mass function of galaxies in groups. We find that an abundance matching model that associates galaxies with the peak circular velocity of their halos is in good agreement with the data, when scatter of 0.20 {+-} 0.03 dex in stellar mass at a given peak velocity is included. This confirms the theoretical expectation that the stellar mass of galaxies is tightly correlated with the potential wells of their dark matter halos before they are impacted by larger structures. The data put tight constraints on the satellite fraction of galaxies as a function of galaxy stellar mass and on the scatter between halo and galaxy properties, and rule out several alternative abundance matching models that have been considered. This will yield important constraints for galaxy formation models, and also provides encouraging indications that the galaxy-halo connection can be modeled with sufficient fidelity for future precision studies of the dark universe.

Reddick, Rachel M.; Wechsler, Risa H.; Behroozi, Peter S. [Kavli Institute for Particle Astrophysics and Cosmology, Physics Department, Stanford University, Stanford, CA 94305 (United States); Tinker, Jeremy L., E-mail: rmredd@stanford.edu, E-mail: rwechsler@stanford.edu [Physics Department, New York University, New York, NY 10003 (United States)

2013-07-01T23:59:59.000Z

332

Dark Matter Capture in the First Stars: a Power Source and Limit on Stellar Mass  

E-Print Network (OSTI)

The annihilation of weakly interacting massive particles can provide an important heat source for the first (Pop. III) stars, potentially leading to a new phase of stellar evolution known as a "Dark Star". When dark matter (DM) capture via scattering off of baryons is included, the luminosity from DM annihilation may dominate over the luminosity due to fusion, depending on the DM density and scattering cross-section. The influx of DM due to capture may thus prolong the lifetime of the Dark Stars. Comparison of DM luminosity with the Eddington luminosity for the star may constrain the stellar mass of zero metallicity stars; in this case DM will uniquely determine the mass of the first stars. Alternatively, if sufficiently massive Pop. III stars are found, they might be used to bound dark matter properties.

Katherine Freese; Douglas Spolyar; Anthony Aguirre

2008-02-12T23:59:59.000Z

333

First Results of the Phase II SIMPLE Dark Matter Search  

SciTech Connect

We report results of a 14.1 kg d measurement with 15 superheated droplet detectors of total active mass 0.208 kg, comprising the first stage of a 30 kg d Phase II experiment. In combination with the results of the neutron-spin sensitive XENON10 experiment, these results yield a limit of |a{sub p}|<0.32 for M{sub W}=50 GeV/c{sup 2} on the spin-dependent sector of weakly interacting massive particle-nucleus interactions with a 50% reduction in the previously allowed region of the phase space, formerly defined by XENON, KIMS, and PICASSO. In the spin-independent sector, a limit of 2.3x10{sup -5} pb at M{sub W}=45 GeV/c{sup 2} is obtained.

Felizardo, M. [Department of Physics, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Instituto Tecnologico e Nuclear, Estrada Nacional 10, 2686-953 Sacavem (Portugal); Centro de Fisica Nuclear, Universidade de Lisboa, 1649-003 Lisbon (Portugal); Morlat, T.; Girard, T. A. [Centro de Fisica Nuclear, Universidade de Lisboa, 1649-003 Lisbon (Portugal); Department of Physics, Universidade de Lisboa, Campo Grande C8, 1749-016 Lisboa (Portugal); Fernandes, A. C.; Marques, J. G.; Ramos, A. R. [Instituto Tecnologico e Nuclear, Estrada Nacional 10, 2686-953 Sacavem (Portugal); Centro de Fisica Nuclear, Universidade de Lisboa, 1649-003 Lisbon (Portugal); Auguste, M.; Boyer, D.; Cavaillou, A.; Sudre, C.; Poupeney, J. [Laboratoire Souterrain a Bas Bruit, Observatoire de la Cote d'Azur, 84400 Rustrel-Pays d'Apt (France); Payne, R. F.; Miley, H. S. [Pacific Northwest National Laboratory, Richland, Washington 99352 (United States); Puibasset, J. [Centre de Recherche sur la Matiere Divisee CNRS et Universite d'Orleans, 45071 Orleans, cedex 02 France (France)

2010-11-19T23:59:59.000Z

334

Phonon Quasidiffusion in Cryogenic Dark Matter Search Large Germanium Detectors  

SciTech Connect

We present results on quasidiffusion studies in large, 3 inch diameter, 1 inch thick [100] high purity germanium crystals, cooled to 50 mK in the vacuum of a dilution refrigerator, and exposed with 59.5 keV gamma-rays from an Am-241 calibration source. We compare data obtained in two different detector types, with different phonon sensor area coverage, with results from a Monte Carlo. The Monte Carlo includes phonon quasidiffusion and the generation of phonons created by charge carriers as they are drifted across the detector by ionization readout channels.

Leman, S.W.; /MIT, MKI; Cabrera, B.; /Stanford U., Phys. Dept.; McCarthy, K.A.; /MIT, MKI; Pyle, M.; /Stanford U., Phys. Dept.; Resch, R.; /SLAC; Sadoulet, B.; Sundqvist, K.M.; /LBL, Berkeley; Brink, P.L.; Cherry, M.; /Stanford U., Phys. Dept.; Do Couto E Silva, E.; /SLAC; Figueroa-Feliciano, E.; /MIT, MKI; Mirabolfathi, N.; Serfass, B.; /UC, Berkeley; Tomada, A.; /Stanford U., Phys. Dept.

2012-06-04T23:59:59.000Z

335

Recent Results and Future Prospects Cryogenic Dark Matter Search  

E-Print Network (OSTI)

Really Cool Detectors: ZIPs Qinner Qouter A B D C Rbias Ibias SQUID array Phonon D Rfeedback Vqbias 1 µ-mediated Qouter Qinner z y x @50 mK #12;CDMS - UCSC Seminar Richard Schnee Really Cool Detectors: ZIPs Qinner two towers of 6 detectors each in 2003 "Tower 1" same 4 Ge (1 kg) and 2 Si (0.2 kg) ZIPs run

California at Santa Cruz, University of

336

The Particle World Dark Matter | U.S. DOE Office of Science (SC)  

Office of Science (SC) Website

Dark Matter Dark Matter High Energy Physics (HEP) HEP Home About Research Snowmass / P5 Planning Process Intensity Frontier Cosmic Frontier Theoretical Physics Advanced Technology R&D Accelerator R&D Stewardship Research Highlights .pdf file (13.1MB) Questions for the Universe Einstein's Dream of Unified Forces The Particle World The Birth of the Universe Accomplishments Facilities Science Highlights Benefits of HEP Funding Opportunities Advisory Committees News & Resources Contact Information High Energy Physics U.S. Department of Energy SC-25/Germantown Building 1000 Independence Ave., SW Washington, DC 20585 P: (301) 903-3624 F: (301) 903-2597 E: sc.hep@science.doe.gov More Information » Questions for the Universe Dark Matter Print Text Size: A A A RSS Feeds FeedbackShare Page

337

Impact of Dark Matter Microhalos on Signatures for Direct and Indirect Detection  

E-Print Network (OSTI)

Detecting dark matter as it streams through detectors on Earth relies on knowledge of its phase space density on a scale comparable to the size of our solar system. Numerical simulations predict that our Galactic halo contains an enormous hierarchy of substructures, streams and caustics, the remnants of the merging hierarchy that began with tiny Earth mass microhalos. If these bound or coherent structures persist until the present time, they could dramatically alter signatures for the detection of weakly interacting elementary particle dark matter (WIMP). Using numerical simulations that follow the coarse grained tidal disruption within the Galactic potential and fine grained heating from stellar encounters, we find that microhalos, streams and caustics have a negligible likelihood of impacting direct detection signatures implying that dark matter constraints derived using simple smooth halo models are relatively robust. We also find that many dense central cusps survive, yielding a small enhancement in the signal for indirect detection experiments.

Aurel Schneider; Lawrence M. Krauss; Ben Moore

2010-04-30T23:59:59.000Z

338

THE FORMATION OF SHELL GALAXIES SIMILAR TO NGC 7600 IN THE COLD DARK MATTER COSMOGONY  

Science Conference Proceedings (OSTI)

We present new deep observations of 'shell' structures in the halo of the nearby elliptical galaxy NGC 7600, alongside a movie of galaxy formation in a cold dark matter (CDM) universe. The movie, based on an ab initio cosmological simulation, shows how continuous accretion of clumps of dark matter and stars creates a swath of diffuse circumgalactic structures. The disruption of a massive clump on a near-radial orbit creates a complex system of transient concentric shells which bare a striking resemblance to those of NGC 7600. With the aid of the simulation we interpret NGC 7600 in the context of the CDM model.

Cooper, Andrew P. [Max Planck Institut fuer Astrophysik, Karl-Schwarzschild-Str. 1, D-85741 Garching (Germany); Martinez-Delgado, David [Max Planck Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany); Helly, John; Frenk, Carlos; Cole, Shaun [Institute for Computational Cosmology, Department of Physics, University of Durham, South Road, DH1 3LE Durham (United Kingdom); Crawford, Ken [Rancho del Sol Observatory, Camino, CA 95709 (United States); Zibetti, Stefano [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen (Denmark); Carballo-Bello, Julio A. [Instituto de Astrofisica de Canarias, Via Lactea s/n, E-38205 La Laguna, Tenerife (Spain); Jay GaBany, R., E-mail: acooper@mpa-garching.mpg.de, E-mail: delgado@mpia-hd.mpg.de [Black Bird Observatory II, 5660 Brionne Drive, San Jose, CA 95118 (United States)

2011-12-10T23:59:59.000Z

339

CMB bounds on dark matter annihilation: nucleon energy-losses after recombination  

E-Print Network (OSTI)

We consider the propagation and energy losses of protons and anti-protons produced by dark matter annihilation at redshifts 100energy injected into e^\\pm and \\gamma's, but their interactions are normally neglected when deriving CMB bounds from altered recombination histories. Here, we follow numerically the energy-loss history of typical protons/antiprotons in the cosmological medium. We show that about half of their energy is channeled into photons and e^\\pm, and we present a simple prescription to estimate the corresponding strengthening of the CMB bounds on the dark matter annihilation cross section.

Weniger, Christoph; Iocco, Fabio; Bertone, Gianfranco

2013-01-01T23:59:59.000Z

340

Empirical testing of Tsallis' Thermodynamics as a model for dark matter halos  

E-Print Network (OSTI)

We study a dark matter halo model from two points of view: the ``stellar polytrope'' (SP) model coming from Tsallis' thermodynamics, and the one coming from the Navarro-Frenk-White (NFW) paradigm. We make an appropriate comparison between both halo models and analyzing the relations between the global physical parameters of observed galactic disks, coming from a sample of actual galaxies, with the ones of the unobserved dark matter halos, we conclude that the SP model is favored over the NFW model in such a comparison.

Dario Nunez; Roberto A. Sussman; Jesus Zavala; Luis G. Cabral-Rosetti; Tonatiuh Matos

2006-04-06T23:59:59.000Z

Note: This page contains sample records for the topic "dark matter searches" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


341

Dark matter and Higgs boson collider implications of fermions in an abelian-gauged hidden sector  

E-Print Network (OSTI)

We add fermions to an abelian-gauged hidden sector. We show that the lightest can be the dark matter with the right thermal relic abundance, and discovery is within reach of upcoming dark matter detectors. We also show that these fermions change Higgs boson phenomenology at the Large Hadron Collider (LHC), and in particular could induce a large invisible width to the lightest Higgs boson state. Such an invisibly decaying Higgs boson can be discovered with good significance in the vector boson fusion channel at the LHC.

Shrihari Gopalakrishna; Seung J. Lee; James D. Wells

2009-04-13T23:59:59.000Z

342

Direct Majorana quasiparticles heat capacity observation by $^3$He Dark Matter detector  

E-Print Network (OSTI)

The Majorana fermion: fermion that is its own antiparticle, was predicted by Majorana in 1937. No fundamental particles are known to be Majorana fermions, although there are speculations that the neutrino is one. Many proposed theories assumes that the mysterious 'dark matter', which forms the greatest part of the universe, is composed of Majorana fermions. Even Majorana does not yet observed as a stable particle, its can be also exist as a quasiparticle in the edge of topological isolators. Here we reports the Dark Matter bolometer time constant deviation which is the result of additional Majorana heat capacity.

Yury Bunkov

2013-03-28T23:59:59.000Z

343

Information content in the halo-model dark-matter power spectrum II: Multiple cosmological parameters  

E-Print Network (OSTI)

We investigate the cosmological Fisher information in the non-linear dark-matter power spectrum in the context of the halo model. We find that there is a plateau in information content on translinear scales which is generic to all cosmological parameters we tried. There is a rise in information on smaller scales, but we find that it is quite degenerate among different cosmological parameters (except, perhaps, the tilt). This suggests that it could be difficult to constrain cosmological parameters using the non-linear regime of the dark-matter power spectrum. We suggest ways to get around this problem, such as removing the largest haloes from consideration in survey analysis.

Mark C. Neyrinck; István Szapudi

2006-10-06T23:59:59.000Z

344

The Connection between Galaxies and Dark Matter Structures in the Local Universe  

SciTech Connect

We provide new constraints on the connection between galaxies in the local Universe, identified by the Sloan Digital Sky Survey (SDSS), and dark matter halos and their constituent substructures in the {Lambda}CDM model using WMAP7 cosmological parameters. Predictions for the abundance and clustering properties of dark matter halos, and the relationship between dark matter hosts and substructures, are based on a high-resolution cosmological simulation, the Bolshoi simulation. We associate galaxies with dark matter halos and subhalos using subhalo abundance matching, and perform a comprehensive analysis which investigates the underlying assumptions of this technique including (a) which halo property is most closely associated with galaxy stellar masses and luminosities, (b) how much scatter is in this relationship, and (c) how much subhalos can be stripped before their galaxies are destroyed. The models are jointly constrained by new measurements of the projected two-point galaxy clustering and the observed conditional stellar mass function of galaxies in groups. We find that an abundance matching model that associates galaxies with the peak circular velocity of their halos is in good agreement with the data, when scatter of 0.20 {+-} 0.03 dex in stellar mass at a given peak velocity is included. This confirms the theoretical expectation that the stellar mass of galaxies is tightly correlated with the potential wells of their dark matter halos before they are impacted by larger structures. The data put tight constraints on the satellite fraction of galaxies as a function of galaxy stellar mass and on the scatter between halo and galaxy properties, and rule out several alternative abundance matching models that have been considered. This will yield important constraints for galaxy formation models, and also provides encouraging indications that the galaxy - halo connection can be modeled with sufficient fidelity for future precision studies of the dark Universe.

Reddick, Rachel M.; Wechsler, Risa H.; Tinker, Jeremy L.; Behroozi, Peter S.

2012-07-11T23:59:59.000Z

345

Testing a DBI model for the unification of dark matter and dark energy with Gamma-Ray Bursts  

E-Print Network (OSTI)

We study the range of consistency of a model based on a nonlinear scalar field Dirac-Born-Infeld action for the unification of dark matter and dark energy using Gamma-Ray Bursts at high-redshifts. We use the sample of 59 high-redshift GRBs reported by Wei (2010), calibrated at low redshifts with the Union 2 sample of SNe Ia, thus avoiding the circularity problem. In this analysis, we also include the CMB7-year data and the baryonic acoustic peak BAO. Besides, it is calculated the parameter of the equation of state $w$, the deceleration parameter $q_0$ and the redshift of the transition to the decelerate-accelerated phase $z_t$.

Ariadna Montiel; Nora Bretón

2012-02-14T23:59:59.000Z

346

Nonbaryonic dark matter and scalar field coupled with a transversal interaction plus decoupled radiation  

E-Print Network (OSTI)

We analyze a universe filled with interacting dark matter, a scalar field accommodated as dark radiation along with dark energy plus a decoupled radiation term within the framework of spatially flat Friedmann-Robertson-Walker (FRW) spacetime. We work in a three-dimensional internal space spanned by the interaction vector and use a transversal interaction $\\mathbf{Q_t}$ for solving the source equation in order to find all the interacting component energy densities. We asymptotically reconstruct the scalar field and potential from an early radiation era to the late dominate dark energy one, passing through an intermediate epoch dominated by dark matter. We apply the $\\chi^{2}$ method to the updated observational Hubble data for constraining the cosmic parameters, contrast with the Union 2 sample of supernovae, and analyze the amount of dark energy in the radiation era. It turns out that our model fulfills the severe bound of $\\Omega_{\\rm \\phi}(z\\simeq 1100)<0.018$ at $2\\sigma$ level, is consistent with the r...

Chimento, Luis P

2013-01-01T23:59:59.000Z

347

A MICROLENSING MEASUREMENT OF DARK MATTER FRACTIONS IN THREE LENSING GALAXIES  

Science Conference Proceedings (OSTI)

Direct measurements of dark matter distributions in galaxies are currently only possible through the use of gravitational lensing observations. Combinations of lens modeling and stellar velocity dispersion measurements provide the best constraints on dark matter distributions in individual galaxies, however they can be quite complex. In this paper, we use observations and simulations of gravitational microlensing to measure the smooth (dark) matter mass fraction at the position of lensed images in three lens galaxies: MG 0414+0534, SDSS J0924+0219, and Q2237+0305. The first two systems consist of early-type lens galaxies, and both display a flux ratio anomaly in their close image pair. Anomalies such as these suggest that a high smooth matter percentage is likely, and indeed we prefer {approx}50% smooth matter in MG 0414+0534 and {approx}80% in SDSS J0924+0219 at the projected locations of the lensed images. Q2237+0305 differs somewhat in that its lensed images lie in the central kiloparsec of the barred spiral lens galaxy, where we expect stars to dominate the mass distribution. In this system, we find a smooth matter percentage that is consistent with zero.

Bate, N. F.; Webster, R. L.; Wyithe, J. S. B. [School of Physics, University of Melbourne, Parkville, Vic. 3010 (Australia); Floyd, D. J. E., E-mail: nbate@physics.unimelb.edu.au [OCIW, Las Campanas Observatory, Casilla 601, Colina El Pino, La Serena, Chile. (Chile)

2011-04-10T23:59:59.000Z

348

DETECTING TRIAXIALITY IN THE GALACTIC DARK MATTER HALO THROUGH STELLAR KINEMATICS  

Science Conference Proceedings (OSTI)

Assuming the dark matter halo of the Milky Way to be a non-spherical potential (i.e., triaxial, prolate, oblate), we show how the assembling process of the Milky Way halo may have left long-lasting stellar halo kinematic fossils due to the shape of the dark matter halo. In contrast with tidal streams, which are associated with recent satellite accretion events, these stellar kinematic groups will typically show inhomogeneous chemical and stellar population properties. However, they may be dominated by a single accretion event for certain mass assembling histories. If the detection of these peculiar kinematic stellar groups were confirmed, they would be the smoking gun for the predicted triaxiality of dark halos in cosmological galaxy formation scenarios.

Rojas-Nino, Armando; Valenzuela, Octavio; Pichardo, Barbara [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, A.P. 70-264, 04510, Mexico, D.F., Universitaria, D.F. (Mexico); Aguilar, Luis A., E-mail: octavio@astro.unam.mx, E-mail: barbara@astro.unam.mx [Observatorio Astronomico Nacional, Universidad Nacional Autonoma de Mexico, Apdo. postal 877, 22800 Ensenada (Mexico)

2012-10-01T23:59:59.000Z

349

Gravity-driven Transport along Cylindrical Topological Defects : Possible Dark Matter and Nearly Frictionless States  

E-Print Network (OSTI)

The gravity-driven flow along an annular topological defect (string) with transversely corrugations is investigated by using the verified transition-rate model and boundary perturbation method. We found that for certain activation volume and energy there exists possible frictionless states which might be associated with the missing momentum of inertia or dark matter.

Zotin K. -H. Chu

2009-11-07T23:59:59.000Z

350

Angular Signatures of Dark Matter in the Diffuse Gamma Ray Background  

E-Print Network (OSTI)

Dark matter annihilating in our Galaxy's halo and elsewhere in the universe is expected to generate a diffuse flux of gamma rays, potentially observable with next generation satellite-based experiments, such as GLAST. In this article, we study the signatures of dark matter in the angular distribution of this radiation, in particular the deterministic ones. Pertaining to the extragalactic contribution, we discuss the effect of the motion of the solar system with respect to the cosmological rest frame, and anisotropies due to the structure of our local universe. For the gamma ray flux from dark matter in our own Galactic halo, we discuss the effects of the offset position of the solar system, the Compton-Getting effect, the asphericity of the Milky Way halo, and the signatures of nearby substructure. We explore the prospects for the detection of these features by the GLAST satellite and find that, if ~10% or more of the diffuse gamma ray background observed by EGRET is the result of dark matter annihilations, then GLAST should be sensitive to anisotropies at the sub-percent level. Such precision would be sufficient to detect many, if not all, of the signatures discussed in this paper.

Dan Hooper; Pasquale D. Serpico

2007-02-12T23:59:59.000Z

351

Abstract: Tracking and Visualizing Evolution of the Universe: In Situ Parallel Dark Matter Halo Merger Trees  

Science Conference Proceedings (OSTI)

We present a framework to study the behavior and properties of cosmological structures called dark matter halos. As part of the framework, we build an evolution history, called halo merger trees, which follows the evolution of the halos over time. The ... Keywords: parallel programming, distributed systems, feature tracking, merger tree

Jay Takle, Katrin Heitmann, Tom Peterka, Deborah Silver, George Zagaris, Salman Habib

2012-11-01T23:59:59.000Z

352

MEASURING DARK MATTER PROFILES NON-PARAMETRICALLY IN DWARF SPHEROIDALS: AN APPLICATION TO DRACO  

SciTech Connect

We introduce a novel implementation of orbit-based (or Schwarzschild) modeling that allows dark matter density profiles to be calculated non-parametrically in nearby galaxies. Our models require no assumptions to be made about velocity anisotropy or the dark matter profile. The technique can be applied to any dispersion-supported stellar system, and we demonstrate its use by studying the Local Group dwarf spheroidal galaxy (dSph) Draco. We use existing kinematic data at larger radii and also present 12 new radial velocities within the central 13 pc obtained with the VIRUS-W integral field spectrograph on the 2.7 m telescope at McDonald Observatory. Our non-parametric Schwarzschild models find strong evidence that the dark matter profile in Draco is cuspy for 20 {<=} r {<=} 700 pc. The profile for r {>=} 20 pc is well fit by a power law with slope {alpha} = -1.0 {+-} 0.2, consistent with predictions from cold dark matter simulations. Our models confirm that, despite its low baryon content relative to other dSphs, Draco lives in a massive halo.

Jardel, John R.; Gebhardt, Karl [Department of Astronomy, The University of Texas, 2515 Speedway, Stop C1400, Austin, TX 78712-1205 (United States)] [Department of Astronomy, The University of Texas, 2515 Speedway, Stop C1400, Austin, TX 78712-1205 (United States); Fabricius, Maximilian H.; Williams, Michael J. [Max-Planck Institut fuer extraterrestrische Physik, Giessenbachstrasse, D-85741 Garching bei Muenchen (Germany)] [Max-Planck Institut fuer extraterrestrische Physik, Giessenbachstrasse, D-85741 Garching bei Muenchen (Germany); Drory, Niv, E-mail: jardel@astro.as.utexas.edu [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Avenida Universidad 3000, Ciudad Universitaria, C.P. 04510 Mexico D.F. (Mexico)] [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Avenida Universidad 3000, Ciudad Universitaria, C.P. 04510 Mexico D.F. (Mexico)

2013-02-15T23:59:59.000Z

353

Towards Closing the Window on Strongly Interacting Dark Matter: Far-Reaching Constraints from Earth's Heat Flow  

E-Print Network (OSTI)

We point out a new and largely model-independent constraint on the dark matter scattering cross section with nucleons, applying when this quantity is larger than for typical weakly interacting dark matter candidates. When the dark matter capture rate in Earth is efficient, the rate of energy deposition by dark matter self-annihilation products would grossly exceed the measured heat flow of Earth. This improves the spin-independent cross section constraints by many orders of magnitude, and closes the window between astrophysical constraints (at very large cross sections) and underground detector constraints (at small cross sections). In the applicable mass range, from about 1 to about 10^{10} GeV, the scattering cross section of dark matter with nucleons is then bounded from above by the latter constraints, and hence must be truly weak, as usually assumed.

Gregory D. Mack; John F. Beacom; Gianfranco Bertone

2007-05-29T23:59:59.000Z

354

Modeling the affect of dark matter distributions in the Milky Way on the component of the cosmic rays energy spectrum as incident on Earth  

E-Print Network (OSTI)

In this thesis, we investigate the effect of dark matter distribution in the galaxy on the positron spectrum on earth. We wrote code to simulate two district dark matter distribution functions as well as the annihilations ...

Kamenetska, Masha

2005-01-01T23:59:59.000Z

355

Hydro-gravitational fragmentation, diffusion and condensation of the primordial plasma, dark-matter and gas  

E-Print Network (OSTI)

The first structures were proto-voids formed in the primordial plasma. Viscous and weak turbulence forces balanced gravitational forces when the scale of causal connection at time 30,000 years matched the viscous and turbulent Schwarz scales of hydro-gravitational theory (Gibson 1996). The photon viscosity allows only weak turbulence from the Reynolds number Re = 200, with fragmentation to give proto-supercluster voids, buoyancy forces, fossil vorticity turbulence, and strong sonic damping. The expanding, cooling, plasma continued fragmentation to proto-galaxy-mass with the density and rate-of-strain preserved as fossils of the weak turbulence and first structure. Turbulence fossilization by self-gravitational buoyancy explains the cosmic microwave background temperature fluctuations, not sonic oscillations in cold-dark-matter fragments. After plasma to gas transition at 300,000 years, gas fragmentation occurred within the proto-galaxies to form proto-globular-star-cluster (PGCs) clouds of small-planetary-mass primordial-fog-particles (PFPs). Dark PGC clumps of frozen PFPs persist as the inner-galaxy-halo dark matter, supporting Schild's 1996 quasar-microlensing interpretation. Non-baryonic dark matter diffused into the plasma proto-cluster-voids and later fragmented as outer-galaxy-halos at diffusive Schwarz scales, indicating light, weakly-collisional fluid particles (possibly neutrinos). Observations support the theory (Gibson and Schild 2003).

Carl H. Gibson

1999-11-15T23:59:59.000Z

356

Matter density perturbations and effective gravitational constant in modified gravity models of dark energy  

E-Print Network (OSTI)

We derive the equation of matter density perturbations on sub-horizon scales for a general Lagrangian density f(R, phi, X) that is a function of a Ricci scalar R, a scalar field phi and a kinetic term X=-(nabla phi)^2/2. This is useful to constrain modified gravity dark energy models from observations of large-scale structure and weak lensing. We obtain the solutions for the matter perturbation delta_m as well as the gravitational potential Phi for some analytically solvable models. In a f(R) dark energy model with the Lagrangian density f(R)=alpha R^{1+m}-Lambda, the growth rates of perturbations exhibit notable differences from those in the standard Einstein gravity unless m is very close to 0. In scalar-tensor models with the Lagrangian density f=F(phi)R+2p(phi,X) we relate the models with coupled dark energy scenarios in the Einstein frame and reproduce the equations of perturbations known in the current literature by making a conformal transformation. We also estimate the evolution of perturbations in both Jordan and Einstein frames when the energy fraction of dark energy is constant during the matter-dominated epoch.

Shinji Tsujikawa

2007-05-08T23:59:59.000Z

357

A NEW PROBE OF THE DISTRIBUTION OF DARK MATTER IN GALAXIES  

SciTech Connect

The scale radius of dark matter halos is a critical parameter for specifying the density distribution of dark matter, and is therefore a fundamental parameter for modeling galaxies. We develop here a novel, observationally motivated probe to quantitatively infer its value within the context of the Navarro, Frenk, and White profile. We demonstrate that disturbances in the extended atomic hydrogen gas disks of galaxies can be analyzed to infer the scale radius of the dark matter halo. Our primary metric is the phase (i.e., the shape of the spiral) of the m = 1 mode of the disturbance in the outskirts of the gas disk, which we take to be produced by a tidal interaction. We apply the method to the Whirlpool galaxy, which has an optically visible satellite. We infer a scale radius of {approx}17 kpc for M51, which is consistent with expectations from dissipationless cosmological simulations. We explore potential degeneracies due to orbital inclination, initial conditions, satellite mass, and pericenter approach distance, and find our results to be relatively insensitive to these considerations. Our method of tracing the dark potential well through observed disturbances in outer gas disks is complementary to gravitational lensing.

Chakrabarti, Sukanya, E-mail: chakrabarti@astro.rit.edu [School of Physics and Astronomy, Rochester Institute of Technology, 84 Lomb Memorial Drive, Rochester, NY 14623 (United States)

2013-07-10T23:59:59.000Z

358

Model for a Universe described by a non-minimally coupled scalar field and interacting dark matter  

E-Print Network (OSTI)

In this work it is investigated the evolution of a Universe where a scalar field, non-minimally coupled to space-time curvature, plays the role of quintessence and drives the Universe to a present accelerated expansion. A non-relativistic dark matter constituent that interacts directly with dark energy is also considered, where the dark matter particle mass is assumed to be proportional to the value of the scalar field. Two models for dark matter pressure are considered: the usual one, pressureless, and another that comes from a thermodynamic theory and relates the pressure with the coupling between the scalar field and the curvature scalar. Although the model has a strong dependence on the initial conditions, it is shown that the mixture consisted of dark components plus baryonic matter and radiation can reproduce the expected red-shift behavior of the deceleration parameter, density parameters and luminosity distance.

J. B. Binder; G. M. Kremer

2006-01-25T23:59:59.000Z

359

Sources of cosmic microwave radiation and dark matter identified: millimeter black holes (m.b.h.)  

E-Print Network (OSTI)

The universe is filled with blackbody millimeter radiation (CMBR), temperature 2.7{\\deg} Kelvin[1]. Big-bang cosmology explains this by the initial thermalization of photons scattered by electrons[2]. This explanation requires ad hoc previous existence of photons and thermal electrons. On the other hand most of the mass of the universe is unknown dark matter3. It explains anomalous dynamical properties, like that of stars in galaxies[4,5,6] . Alternatively the anomalies have been explained by adjusting and modifying well known laws ("Modified Newtonian dynamics"[7]). Here we show that millimeter black holes (m.b.h.) explain both: the background radiation, by its partial "evaporation", and the dark matter. Black holes emit blackbody radiation (Hawking[8] evaporation), and this is what is observed in the CMBR. Millimeter size black holes emit blackbody radiation at a temperature of 2.7{\\deg} Kelvin, and this is the resulting CMBR . Partial evaporation of ~10^30 m.b.h. gives the observed background field of photons being emitted and absorbed at the same rate by the m.b.h. The number of photons is constant, as observed. Their temperature decreases with time because the mass of the m.b.h. (and therefore its size) increases with time (the mass-boom effect[9]). The total mass of the m.b.h. is the dark matter. Hence dark matter is not so "dark" after all. Two important cosmological items are here identified by only one source: millimeter black holes.

Antonio Alfonso-Faus; Marius Josep Fullana i Alfonso

2010-04-13T23:59:59.000Z

360

Dark Matter Constraints from Observations of 25 Milky Way Satellite Galaxies with the Fermi Large Area Telescope  

E-Print Network (OSTI)

The dwarf spheroidal satellite galaxies of the Milky Way are some of the most dark-matter-dominated objects known. Due to their proximity, high dark matter content, and lack of astrophysical backgrounds, dwarf spheroidal galaxies are widely considered to be among the most promising targets for the indirect detection of dark matter via gamma rays. Here we report on gamma-ray observations of 25 Milky Way dwarf spheroidal satellite galaxies based on 4 years of Fermi Large Area Telescope (LAT) data. None of the dwarf galaxies are significantly detected in gamma rays, and we present gamma-ray flux upper limits between 500 MeV and 500 GeV. We determine the dark matter content of 18 dwarf spheroidal galaxies from stellar kinematic data and combine LAT observations of 15 dwarf galaxies to constrain the dark matter annihilation cross section. We set some of the tightest constraints to date on the the annihilation of dark matter particles with masses between 2 GeV and 10 TeV into prototypical Standard Model channels. We find these results to be robust against systematic uncertainties in the LAT instrument performance, diffuse gamma-ray background modeling, and assumed dark matter density profile.

The Fermi-LAT Collaboration; :; M. Ackermann; A. Albert; B. Anderson; L. Baldini; J. Ballet; G. Barbiellini; D. Bastieri; K. Bechtol; R. Bellazzini; E. Bissaldi; E. D. Bloom; E. Bonamente; A. Bouvier; T. J. Brandt; J. Bregeon; M. Brigida; P. Bruel; R. Buehler; S. Buson; G. A. Caliandro; R. A. Cameron; M. Caragiulo; P. A. Caraveo; C. Cecchi; E. Charles; A. Chekhtman; J. Chiang; S. Ciprini; R. Claus; J. Cohen-Tanugi; J. Conrad; F. D'Ammando; A. de Angelis; C. D. Dermer; S. W. Digel; E. do Couto e Silva; P. S. Drell; A. Drlica-Wagner; R. Essig; C. Favuzzi; E. C. Ferrara; A. Franckowiak; Y. Fukazawa; S. Funk; P. Fusco; F. Gargano; D. Gasparrini; N. Giglietto; M. Giroletti; G. Godfrey; G. A. Gomez-Vargas; I. A. Grenier; Guiriec; M. Gustafsson; M. Hayashida; E. Hays; J. Hewitt; R. E. Hughes; T. Jogler; T. Kamae; J. Knödlseder; D. Kocevski; M. Kuss; . Larsson; L. Latronico; M. Llena Garde; F. Longo; F. Loparco; M. N. Lovellette; P. Lubrano; G. Martinez; M. Mayer; M. N. Mazziotta; P. F. Michelson; W. Mitthumsiri; T. Mizuno; A. A. Moiseev; M. E. Monzani; A. Morselli; I. V. Moskalenko; S. Murgia; R. Nemmen; E. Nuss; T. Ohsugi; E. Orlando; J. F. Ormes; J. S. Perkins; F. Piron; G. Pivato; T. A. Porter; S. Rainň; R. Rando; M. Razzano; S. Razzaque; A. Reimer; O. Reimer; S. Ritz; M. Sŕnchez-Conde; N. Sehgal; C. Sgrň; E. J. Siskind; P. Spinelli; L. Strigari; D. J. Suson; H. Tajima; H. Takahashi; J. B. Thayer; L. Tibaldo; M. Tinivella; D. F. Torres; Y. Uchiyama; T. L. Usher; J. Vandenbroucke; G. Vianello; V. Vitale; M. Werner; B. L. Winer; K. S. Wood; M. Wood; G. Zaharijas; S. Zimmer

2013-10-02T23:59:59.000Z

Note: This page contains sample records for the topic "dark matter searches" from the National Library of EnergyBeta (NLEBeta).
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361

Non-Gaussianity in the Cosmic Microwave Background Induced by Dipolar Dark Matter  

E-Print Network (OSTI)

In previous work [L. Blanchet and A. Le Tiec, Phys. Rev. D 80, 023524 (2009)], motivated by the phenomenology of dark matter at galactic scales, a model of dipolar dark matter (DDM) was introduced. At linear order in cosmological perturbations, the dynamics of the DDM was shown to be identical to that of standard cold dark matter (CDM). In this paper, the DDM model is investigated at second order in cosmological perturbation theory. We find that the internal energy of the DDM fluid modifies the curvature perturbation generated by CDM with a term quadratic in the dipole field. This correction induces a new type of non-Gaussianity in the bispectrum of the curvature perturbation with respect to standard CDM. Leaving unspecified the primordial amplitude of the dipole field, which could in principle be determined by a more fundamental description of DDM, we find that, in contrast with usual models of primordial non-Gaussianities, the non-Gaussianity induced by DDM increases with time after the radiation-matter equ...

Blanchet, Luc; Tiec, Alexandre Le; Marsat, Sylvain

2013-01-01T23:59:59.000Z

362

An equation of state for dark matter in the Milky Way  

E-Print Network (OSTI)

Dark matter, believed to be present in many galaxies, is interpreted as a hydrodynamical system in interaction with the gravitational field and with nothing else. The gravitational field of our Galaxy can be inferred from observation of orbital velocities of the visible stars, in a first approximation in which the field is taken to be due to the distribution of dark matter only. An equation of state is determined by the gravitational field via the equations of motion. To arrive at an estimate of the distribution of dark matter in our galaxy, and simultaneously learn something about the gravitational field in the inner regions, the following strategy was adopted: 1. The observed rotation curves suggest an expression for the newtonian potential, valid in the outer region. 2. The assumption of a quasi stationary, spherically symmetric distribution of dark matter then leads to a unique equation of state. 3. This equation of state is assumed to be valid all the way to the center (though of course the newtonian approximation is not). 4. Using this equation of state, together with Einstein's equations and the relativistic hydrostatic condition, we calculate the metric and the matter density throughout the galaxy. The solutions are regular all the way to the center; there is no indication of a structure of the type of a Black Hole. The equation of state that is thus determined experimentally is of the type used by Chandrasekhar and others for the degenerate Fermi gas. In the approximation of weak fields the associated "sinh-Emden" equation has a global, nonsingular solution.

Christian Fronsdal; Thomas J. Wilcox

2012-04-08T23:59:59.000Z

363

The Morphology of the Galactic Dark Matter Synchrotron Emission with Self-Consistent Cosmic Ray Diffusion Models  

E-Print Network (OSTI)

A generic prediction in the paradigm of weakly interacting dark matter is the production of relativistic particles from dark matter pair-annihilation in regions of high dark matter density. Ultra-relativistic electrons and positrons produced in the center of the Galaxy by dark matter annihilation should produce a diffuse synchrotron emission. While the spectral shape of the synchrotron dark matter haze depends on the particle model (and secondarily on the galactic magnetic fields), the morphology of the haze depends primarily on (1) the dark matter density distribution, (2) the galactic magnetic field morphology, and (3) the diffusion model for high-energy cosmic-ray leptons. Interestingly, an unidentified excess of microwave radiation with characteristics similar to those predicted by dark matter models has been claimed to exist near the galactic center region in the data reported by the WMAP satellite, and dubbed the "WMAP haze". In this study, we carry out a self-consistent treatment of the variables enumerated above, enforcing constraints from the available data on cosmic rays, radio surveys and diffuse gamma rays. We outline and make predictions for the general morphology and spectral features of a "dark matter haze" and we compare them to the WMAP haze data. We also characterize and study the spectrum and spatial distribution of the inverse Compton emission resulting from the same population of energetic electrons and positrons. We point out that the spectrum and morphology of the radio emission at different frequencies is a powerful diagnostics to test whether a galactic synchrotron haze indeed originates from dark matter annihilation.

Tim Linden; Stefano Profumo; Brandon Anderson

2010-04-22T23:59:59.000Z

364

Search for MeV dark photons in a light-shining-through-walls experiment at CERN  

E-Print Network (OSTI)

In addition to gravity, there might be another very weak interaction between the ordinary and dark matter transmitted by U'(1) gauge bosons A' (dark photons) mixing with our photons. If such A's exist, they could be searched for in a light-shining-through-a-wall experiment with a high energy electron beam. The electron energy absorption in a calorimeter (CAL1) is accompanied by the emission of bremsstrahlung A's in the reaction eZ -> eZA' of electrons scattering on nuclei due to the photon - A' mixing. A part of the primary beam energy is deposited in the CAL1, while the rest of the energy is transmitted by the A' through the "CAL1 wall" and deposited in another downstream calorimeter CAL2 by the e+e- pair from the A'->e+e- decay in flight. Thus, the A's could be observed by looking for an excess of events with the two-shower signature generated by a single high energy electron in the CAL1 and CAL2. A proposal to perform such an experiment to probe the still unexplored area of the mixing strength 10^{-5} < \\epsilon < 10^{-3} and masses M_{A'} < 100 MeV by using 10-300 GeV electron beams from the CERN SPS is presented. The experiment can provide complementary coverage of the parameter space, which is intended to be probed by other searche

S. N. Gninenko

2013-08-29T23:59:59.000Z

365

Is the Dark Matter interpretation of the EGRET gamma ray excess compatible with antiproton measurements?  

E-Print Network (OSTI)

The diffuse galactic EGRET gamma ray data show a clear excess for energies above 1 GeV in comparison with the expectations from conventional galactic models. This excess shows all the features expected from Dark Matter WIMP Annihilation: a)it is present and has the same spectrum in all sky directions, not just in the galactic plane, as expected for WIMP annihilation b) it shows an interesting substructure in the form of a doughnut shaped ring at 14 kpc from the centre of the galaxy, where a ring of stars indicated the probable infall of a dwarf galaxy. From the spectral shape of the excess the WIMP mass is estimated to be between 50 and 100 GeV, while from the intensity the halo profile is reconstructed, which is shown to explain the peculiar change of slope in the rotation curve at about 11 kpc (due to the ring of DM at 14 kpc). Recently it was claimed by Bergstrom et al. that the DM interpretation of the EGRET gamma ray excess is excluded by the antiproton fluxes, since in their propagation model with isotropic diffusion the flux of antiprotons would be far beyond the observed flux. However, the propagation can be largely anisotropic, because of the convection of particles perpendicular to the disc and inhomogeneities in the local environment. It is shown that anisotropic propagation can reduce the antiproton yield by an order of magnitude, while still being consistent with the B/C ratio. Therefore it is hard to use antiprotons to search for {\\it light} DM particles, which yield a similar antiproton spectrum as the background, but the antiprotons are a perfect means to tune the many degenerate parameters in the propagation models.

W. de Boer; I. Gebauer; C. Sander; M. Weber; V. Zhukov

2006-12-16T23:59:59.000Z

366

Extending the Sensitivity to the Detection of WIMP Dark Matter with an Improved Understanding of the Limiting Neutron Backgrounds  

SciTech Connect

The Cryogenic Dark Matter Search (CDMS) uses position-sensitive Germanium and Silicon crystals in the direct detection of Weakly Interacting Massive Particles (WIMPs) believed to constitute most of the dark matter in the Universe. WIMP interactions with matter being rare, identifying and eliminating known backgrounds is critical for detection. Event-by-event discrimination by the detectors rejects the predominant gamma and beta backgrounds while Monte Carlo simulations help estimate, and subtract, the contribution from the neutrons. This thesis describes the effort to understand neutron backgrounds as seen in the two stages of the CDMS search for WIMPs. The first stage of the experiment was at a shallow site at the Stanford Underground Facility where the limiting background came from high-energy neutrons produced by cosmic-ray muon interactions in the rock surrounding the cavern. Simulations of this background helped inform the analysis of data from an experimental run at this site and served as input for the background reduction techniques necessary to set new exclusion limits on the WIMP-nucleon cross-section, excluding new parameter space for WIMPs of masses 8-20 GeV/c{sup 2}. This thesis considers the simulation methods used as well as how various event populations in the data served as checks on the simulations to allow them to be used in the interpretation of the WIMP-search data. The studies also confirmed the presence of a limiting neutron background at the shallow site, necessitating the move to the 713-meter deep Soudan Underground Facility. Similar computer-based studies helped quantify the neutron background seen at the deeper site and informed the analysis of the data emerging from the first physics run of the experiment at Soudan. In conjunction with the WIMP-search and calibration data, the simulations confirmed that increased depth considerably reduced the neutron backgrounds seen, greatly improving the sensitivity to WIMP detection. The data run set an upper limit of 4 x 10{sup -43} on the WIMP-nucleon cross section for a WIMP mass of 60 GeV/c{sup 2} . Upper limits to the rate of background neutrons have also been determined.

Kamat, Sharmila; /Case Western Reserve U.

2005-01-01T23:59:59.000Z

367

Two Component Dark Matters in S_4 x Z_2 Flavor Symmetric Extra U(1) Model  

E-Print Network (OSTI)

We study cosmic-ray anomaly observed by PAMELA based on E_6 inspired extra U(1) model with S_4 x Z_2 flavor symmetry. In our model, the lightest flavon has very long lifetime of O(10^{18)) second which is longer than the age of the universe, but not long enough to explain the PAMELA result ~ O(10^{26}) sec. Such a situation could be avoidable by considering that the flavon is not the dominant component of dark matters and the dominant one is the lightest neutralino. With appropriate parameter set, density parameter of dark matter and over-abundance of positron flux in cosmic-ray are realized at the same time. There is interesting correlation between spectrum of positron flux and V_{MNS}. No excess of anti-proton in cosmic-ray suggests that sfermions are heavier than 4 TeV and the masses of the light Higgs bosons are degenerated.

Daikoku, Yasuhiro; Toma, Takashi

2011-01-01T23:59:59.000Z

368

Two Component Dark Matters in S_4 x Z_2 Flavor Symmetric Extra U(1) Model  

E-Print Network (OSTI)

We study cosmic-ray anomaly observed by PAMELA based on E_6 inspired extra U(1) model with S_4 x Z_2 flavor symmetry. In our model, the lightest flavon has very long lifetime of O(10^{18)) second which is longer than the age of the universe, but not long enough to explain the PAMELA result ~ O(10^{26}) sec. Such a situation could be avoidable by considering that the flavon is not the dominant component of dark matters and the dominant one is the lightest neutralino. With appropriate parameter set, density parameter of dark matter and over-abundance of positron flux in cosmic-ray are realized at the same time. There is interesting correlation between spectrum of positron flux and V_{MNS}. No excess of anti-proton in cosmic-ray suggests that sfermions are heavier than 4 TeV and the masses of the light Higgs bosons are degenerated.

Yasuhiro Daikoku; Hiroshi Okada; Takashi Toma

2011-06-23T23:59:59.000Z

369

Distinguishing Supersymmetry From Universal Extra Dimensions or Little Higgs Models With Dark Matter Experiments  

SciTech Connect

There are compelling reasons to think that new physics will appear at or below the TeV-scale. It is not known what form this new physics will take, however. Although The Large Hadron collider is very likely to discover new particles associated with the TeV-scale, it may be difficult for it to determine the nature of those particles, whether superpartners, Kaluza-Klein modes or other states. In this article, we consider how direct and indirect dark matter detection experiments may provide information complementary to hadron colliders, which can be used to discriminate between supersymmetry, models with universal extra dimensions, and Little Higgs theories. We find that, in many scenarios, dark matter experiments can be effectively used to distinguish between these possibilities.

Hooper, Dan; Zaharijas, Gabrijela; /Fermilab

2006-12-01T23:59:59.000Z

370

Dark Matter Capture in the first star: a Power source and a limit on Stellar Mass  

E-Print Network (OSTI)

Weakly interacting massive particles, which are their own antiparticles, can annihilate and provide an important heat source for the first (zero-metallicity) stars. When dark matter (DM) capture via scattering off of baryons is included, the luminosity from DM annihilation may dominate over the luminosity due to fusion, depending on the DM density and scattering cross-section. Even more interesting is the possibility that the DM annihilation may exceed the Eddington luminosity and prevent the first stars from growing beyond a limited mass. In such a case, DM will uniquely determine the mass of the first stars. Alternatively, if sufficiently massive zero-metallicity stars are found, they may be used to bound dark matter properties.

Freese, Katherine; Aguirre, Anthony

2008-01-01T23:59:59.000Z

371

Are black holes a serious threat to scalar field dark matter models?  

Science Conference Proceedings (OSTI)

Classical scalar fields have been proposed as possible candidates for the dark matter component of the universe. Given the fact that supermassive black holes seem to exist at the center of most galaxies, in order to be a viable candidate for the dark matter halo a scalar field configuration should be stable in the presence of a central black hole, or at least be able to survive for cosmological time scales. In the present work we consider a scalar field as a test field on a Schwarzschild background, and study under which conditions one can obtain long-lived configurations. We present a detailed study of the Klein-Gordon equation in the Schwarzschild space-time, both from an analytical and numerical point of view, and show that indeed there exist quasistationary solutions that can remain surrounding a black hole for large time scales.

Barranco, Juan; Degollado, Juan Carlos [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Circuito Exterior C.U., A.P. 70-264, Mexico D.F. 04510 (Mexico); Bernal, Argelia; Diez-Tejedor, Alberto; Megevand, Miguel; Alcubierre, Miguel; Nunez, Dario [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Circuito Exterior C.U., A.P. 70-543, Mexico D.F. 04510 (Mexico); Sarbach, Olivier [Instituto de Fisica y Matematicas, Universidad Michoacana de San Nicolas de Hidalgo, Edificio C-3, Ciudad Universitaria, 58040 Morelia, Michoacan (Mexico)

2011-10-15T23:59:59.000Z

372

CONSTRAINTS ON THE SHAPE OF THE MILKY WAY DARK MATTER HALO FROM JEANS EQUATIONS APPLIED TO SLOAN DIGITAL SKY SURVEY DATA  

Science Conference Proceedings (OSTI)

We search for evidence of dark matter in the Milky Way by utilizing the stellar number density distribution and kinematics measured by the Sloan Digital Sky Survey (SDSS) to heliocentric distances exceeding {approx}10 kpc. We employ the cylindrically symmetric form of Jeans equations and focus on the morphology of the resulting acceleration maps, rather than the normalization of the total mass as done in previous, mostly local, studies. Jeans equations are first applied to a mock catalog based on a cosmologically derived N-body+SPH simulation, and the known acceleration (gradient of gravitational potential) is successfully recovered. The same simulation is also used to quantify the impact of dark matter on the total acceleration. We use Galfast, a code designed to quantitatively reproduce SDSS measurements and selection effects, to generate a synthetic stellar catalog. We apply Jeans equations to this catalog and produce two-dimensional maps of stellar acceleration. These maps reveal that in a Newtonian framework, the implied gravitational potential cannot be explained by visible matter alone. The acceleration experienced by stars at galactocentric distances of {approx}20 kpc is three times larger than what can be explained by purely visible matter. The application of an analytic method for estimating the dark matter halo axis ratio to SDSS data implies an oblate halo with q{sub DM} = 0.47 {+-} 0.14 within the same distance range. These techniques can be used to map the dark matter halo to much larger distances from the Galactic center using upcoming deep optical surveys, such as LSST.

Loebman, Sarah R.; Ivezic, Zeljko; Quinn, Thomas R.; Governato, Fabio [Astronomy Department, University of Washington, Box 351580, Seattle, WA 98195-1580 (United States); Brooks, Alyson M. [Department of Astronomy, University of Wisconsin, 475 North Charter Street, Madison, WI 53706 (United States); Christensen, Charlotte R. [Astronomy Department, University of Arizona, Tucson, AZ (United States); Juric, Mario, E-mail: sloebman@astro.washington.edu [LSST Corporation, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)

2012-10-10T23:59:59.000Z

373

The effect of the recoil energy window on the results of direct dark matter experiments  

E-Print Network (OSTI)

The effect of the chosen analysis energy window on the results of a dark matter experiment is exemplified by the curious intersection of the exclusion plots of the XENON10 and the CDMS experiments. After proving that the narrow energy window XENON10 chose to analyze is indeed the cause of such intersection, a method to determine the high-energy extreme of the recoil energy window an experiment should use is obtained.

F. Giuliani

2009-10-09T23:59:59.000Z

374

Constraints on dark matter annihilations from diffuse gamma-ray emission in the Galaxy  

E-Print Network (OSTI)

Recent advances in gamma-ray cosmic ray, infrared and radio astronomy have allowed us to develop a significantly better understanding of the galactic medium properties in the last few years. In this work using the DRAGON code, that numerically solves the CR propagation equation and calculating gamma-ray emissivities in a 2-dimensional grid enclosing the Galaxy, we study in a self consistent manner models for the galactic diffuse gamma-ray emission. Our models are cross-checked to both the available CR and gamma-ray data. We address the extend to which dark matter annihilations in the Galaxy can contribute to the diffuse gamma-ray flux towards different directions on the sky. Moreover we discuss the impact that astrophysical uncertainties of non DM nature, have on the derived gamma-ray limits. Such uncertainties are related to the diffusion properties on the Galaxy, the interstellar gas and the interstellar radiation field energy densities. Light ~10 GeV dark matter annihilating dominantly to hadrons is more strongly constrained by gamma-ray observations towards the inner parts of the Galaxy and influenced the most by assumptions of the gas distribution; while TeV scale DM annihilating dominantly to leptons has its tightest constraints from observations towards the galactic center avoiding the galactic disk plane, with the main astrophysical uncertainty being the radiation field energy density. In addition, we present a method of deriving constraints on the dark matter distribution profile from the diffuse gamma-ray spectra. These results critically depend on the assumed mass of the dark matter particles and the type of its end annihilation products.

Maryam Tavakoli; Ilias Cholis; Carmelo Evoli; Piero Ullio

2013-08-19T23:59:59.000Z

375

Higher Order Curvature Theories of Gravity Matched with Observations: a Bridge Between Dark Energy and Dark Matter Problems  

E-Print Network (OSTI)

Higher order curvature gravity has recently received a lot of attention due to the fact that it gives rise to cosmological models which seem capable of solving dark energy and quintessence issues without using "ad hoc" scalar fields. Such an approach is naturally related to fundamental theories of quantum gravity which predict higher order terms for loop expansions of quantum fields in curved spacetimes. In this framework, we obtain a class of cosmological solutions which are fitted against cosmological data. We reproduce reliable models able to fit high redshift supernovae and WMAP observations. The age of the universe and other cosmological parameters are recovered in this context. Furthermore, in the weak field limit, we obtain gravitational potentials which differ from the Newtonian one because of repulsive corrections increasing with distance. We evaluate the rotation curve of our Galaxy and compare it with the observed data in order to test the viability of these theories and to estimate the scale-length of the correction. It is remarkable that the Milky Way rotation curve is well fitted without the need of any dark matter halo and similar results hold also for other galaxies.

S. Capozziello; V. F. Cardone; S. Carloni; A. Troisi

2004-11-04T23:59:59.000Z

376

Search for stable Strange Quark Matter in lunar soil  

E-Print Network (OSTI)

We report results from a search for strangelets (small chunks of Strange Quark Matter) in lunar soil using the Yale WNSL accelerator as a mass spectrometer. We have searched over a range in mass from A=42 to A=70 amu for nuclear charges 5, 6, 8, 9, and 11. No strangelets were found in the experiment. For strangelets with nuclear charge 8, a concentration in lunar soil higher than $10^{-16}$ is excluded at the 95% confidence level. The implied limit on the strangelet flux in cosmic rays is the most sensitive to date for the covered range and is relevant to both recent theoretical flux predictions and a strangelet candidate event found by the AMS-01 experiment.

Ke Han; Jeffrey Ashenfelter; Alexei Chikanian; William Emmet; Evan Finch; Andreas Heinz; Jes Madsen; Richard Majka; Benjamin Monreal; Jack Sandweiss

2009-03-29T23:59:59.000Z

377

Search for stable Strange Quark Matter in lunar soil  

E-Print Network (OSTI)

We report results from a search for strangelets (small chunks of Strange Quark Matter) in lunar soil using the Yale WNSL accelerator as a mass spectrometer. We have searched over a range in mass from A=42 to A=70 amu for nuclear charges 5, 6, 8, 9, and 11. No strangelets were found in the experiment. For strangelets with nuclear charge 8, a concentration in lunar soil higher than $10^{-16}$ is excluded at the 95% confidence level. The implied limit on the strangelet flux in cosmic rays is the most sensitive to date for the covered range and is relevant to both recent theoretical flux predictions and a strangelet candidate event found by the AMS-01 experiment.

Han, Ke; Chikanian, Alexei; Emmet, William; Finch, Evan; Heinz, Andreas; Madsen, Jes; Majka, Richard; Monreal, Benjamin; Sandweiss, Jack

2009-01-01T23:59:59.000Z

378

Can TeVeS avoid Dark Matter on galactic scales?  

E-Print Network (OSTI)

A fully relativistic analysis of gravitational lensing in TeVeS is presented. By estimating the lensing masses for a set of six lenses from the CASTLES database, and then comparing them to the stellar mass, the deficit between the two is obtained and analysed. Considering a parametrised range for the TeVeS function $mu(y)$, which controls the strength of the modification to gravity, it is found that on galactic scales TeVeS requires additional dark matter with the commonly used $mu(y)$. A soft dependence of the results on the cosmological framework and the TeVeS free parameters is discussed. For one particular form of $mu(y)$, TeVeS is found to require very little dark matter. This choice is however ruled out by rotation curve data. The inability to simultaneously fit lensing and rotation curves for a single form of $mu(y)$ is a challenge to a "no dark matter" TeVeS proposal.

Nick E. Mavromatos; Mairi Sakellariadou; Muhammad Furqaan Yusaf

2009-01-25T23:59:59.000Z

379

Consistent dark matter interpretation for CoGeNT and DAMA/LIBRA  

SciTech Connect

In this paper, we study the recent excess of low-energy events observed by the CoGeNT Collaboration and the annual modulation reported by the DAMA/LIBRA Collaboration, and discuss whether these signals could both be the result of the same elastically scattering dark matter particle. We find that, without channeling but when taking into account uncertainties in the relevant quenching factors, a dark matter candidate with a mass of approximately 7 GeV and a cross section with nucleons of {sigma}{sub DM-N{approx}}2x10{sup -4} pb (2x10{sup -40} cm{sup 2}) could account for both of these observations. We also comment on the events recently observed in the oxygen band of the CRESST experiment and point out that these could potentially be explained by such a particle. Lastly, we compare the region of parameter space favored by DAMA/LIBRA and CoGeNT to the constraints from XENON10, XENON100, and CDMS (Si) and find that these experiments cannot at this time rule out a dark matter interpretation of these signals.

Hooper, Dan [Center for Particle Astrophysics, Fermi National Accelerator Laboratory, Batavia, Illinois 60510 (United States); Department of Astronomy and Astrophysics, University of Chicago, Chicago, Illinois 60637 (United States); Collar, J. I. [Enrico Fermi Institute, KICP and Department of Physics, University of Chicago, Chicago, Illinois 60637 (United States); Hall, Jeter [Center for Particle Astrophysics, Fermi National Accelerator Laboratory, Batavia, Illinois 60510 (United States); McKinsey, Dan [Department of Physics, Yale University, New Haven, Connecticut 06520 (United States); Kelso, Christopher M. [Department of Physics, University of Chicago, Chicago, Illinois 60637 (United States)

2010-12-15T23:59:59.000Z

380

Continuum gamma-ray emission from light dark matter positrons and electrons  

E-Print Network (OSTI)

The annihilation of light dark matter was recently advocated as a possible explanation of the large positron injection rate at the Galactic center deduced from observations by the SPI spectrometer aboard INTEGRAL. The modelling of internal Bremsstrahlung and in-flight annihilation radiations associated to this process drastically reduced the mass range of this light dark matter particle. We estimate critically the various energy losses and radiations involved in the propagation of the positron before its annihilation --in- flight or at rest. Using a simple model with mono-energetic positrons injected and confined to the Galactic bulge, we compute energy losses and gamma-ray radiations caused by ionization, Bremsstrahlung interactions as well as in-flight and at rest annihilation and compare these predictions to the available observations, for various injection energies. Confronting the predictions with observations by the CGRO/EGRET, CGRO/COMPTEL, INTEGRAL/SPI and INTEGRAL/IBIS/ISGRI instruments, we deduce a mass upper bound of 3 to 7.5 MeV/c^2 for the hypothetical light dark matter particle. The most restrictive limit is in agreement with the value previously found by Beacom and Yuksel and was obtained under similar assumptions, while the 7.5 MeV/c^2 value corresponds to more conservative choices and to a partially ionized propagation medium. We stress how the limit depends on the degree of ionization of the propagation medium and how its precision could be improved by a better appraisal of data uncertainties.

P. Sizun; M. Casse; S. Schanne

2006-07-17T23:59:59.000Z

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381

Gamma-ray emission from dark matter wakes of recoiled black holes  

E-Print Network (OSTI)

A new scenario for the emission of high-energy gamma-rays from dark matter annihilation around massive black holes is presented. A black hole can leave its parent halo, by means of gravitational radiation recoil, in a merger event or in the asymmetric collapse of its progenitor star. A recoiled black hole which moves on an almost-radial orbit outside the virial radius of its central halo, in the cold dark matter background, reaches its apapsis in a finite time. Near or at the apapsis passage, a high-density wake extending over a large radius of influence, forms around the black hole. It is shown that significant gamma-ray emission can result from the enhancement of neutralino annihilation in these wakes. At its apapsis passage, a black hole is shown to produce a flash of high-energy gamma-rays whose duration is determined by the mass of the black hole and the redshift at which it is ejected. The ensemble of such black holes in the Hubble volume is shown to produce a diffuse high-energy gamma-ray background whose magnitude is compared to the diffuse emission from dark matter haloes alone.

Roya Mohayaee; Jacques Colin; Joe Silk

2007-09-21T23:59:59.000Z

382

Flat Central Density Profile and Constant DM Surface Density in Galaxies from Scalar Field Dark Matter  

E-Print Network (OSTI)

The scalar field dark matter (SFDM) model proposes that galaxies form by condensation of a scalar field (SF) very early in the universe forming Bose-Einstein Condensates (BEC) drops, i.e., in this model haloes of galaxies are gigantic drops of SF. Here big structures form like in the LCDM model, by hierarchy, thus all the predictions of the LCDM model at big scales are reproduced by SFDM. This model predicts that all galaxies must be very similar and exist for bigger redshifts than in the LCDM model. In this work we show that BEC dark matter haloes fit high-resolution rotation curves of a sample of thirteen low surface brightness galaxies. We compare our fits to those obtained using a Navarro-Frenk-White and Pseudo-Isothermal (PI) profiles and found a better agreement with the SFDM and PI profiles. The mean value of the logarithmic inner density slopes is -0.27 +/- 0.18. As a second result we find a natural way to define the core radius with the advantage of being model-independent. Using this new definition in the BEC density profile we find that the recent observation of the constant dark matter central surface density can be reproduced. We conclude that in light of the difficulties that the standard model is currently facing the SFDM model can be a worthy alternative to keep exploring further.

Victor H. Robles; Tonatiuh Matos

2012-01-14T23:59:59.000Z

383

A Class of Inert N-tuplet Models with Radiative Neutrino Mass and Dark Matter  

E-Print Network (OSTI)

We present a class of models with radiative neutrino mass and stable dark-matter candidates. Neutrino mass is generated by a one-loop diagram with the same topography as Ma's 2006 proposal (which used an inert scalar-doublet and singlet fermion). We generalize this approach and determine all variants with new fields no larger than the adjoint representation. When the neutrino mass diagram contains a Majorana mass insertion there are two possibilities, both of which are known. If the mass insertion is of the Dirac type there are seven additional models, two of which are excluded by direct-detection experiments. The other five models are also constrained, such that only scalar dark-matter is viable. There are cases with an inert singlet, an inert doublet, and an inert triplet, providing a natural setting for inert N-tuplet models of dark matter, with the additional feature of achieving radiative neutrino mass. We show that some of the models admit a simple explanation for the (requisite) discrete symmetry, and ...

Law, Sandy S C

2013-01-01T23:59:59.000Z

384

A Class of Inert N-tuplet Models with Radiative Neutrino Mass and Dark Matter  

E-Print Network (OSTI)

We present a class of models with radiative neutrino mass and stable dark-matter candidates. Neutrino mass is generated by a one-loop diagram with the same topography as Ma's 2006 proposal (which used an inert scalar-doublet and singlet fermion). We generalize this approach and determine all variants with new fields no larger than the adjoint representation. When the neutrino mass diagram contains a Majorana mass insertion there are two possibilities, both of which are known. If the mass insertion is of the Dirac type there are seven additional models, two of which are excluded by direct-detection experiments. The other five models are also constrained, such that only scalar dark-matter is viable. There are cases with an inert singlet, an inert doublet, and an inert triplet, providing a natural setting for inert N-tuplet models of dark matter, with the additional feature of achieving radiative neutrino mass. We show that some of the models admit a simple explanation for the (requisite) discrete symmetry, and briefly discuss cases with representations larger than the adjoint, which can admit a connection to the astrophysical gamma-ray signal.

Sandy S. C. Law; Kristian L. McDonald

2013-05-28T23:59:59.000Z

385

CONSTRAINING THE DISTRIBUTION OF DARK MATTER IN THE INNER GALAXY WITH AN INDIRECT DETECTION SIGNAL: THE CASE OF A TENTATIVE 130 GeV {gamma}-RAY LINE  

SciTech Connect

Dark matter distribution in the very inner region of our Galaxy is still debated. In N-body simulations, a cuspy dark matter halo density profile is favored. Several dissipative baryonic processes, however, are found to be able to significantly flatten dark matter distribution, and a cored dark matter halo density profile is possible. Baryons dominate the gravitational potential in the inner Galaxy, hence a direct constraint on the abundance of dark matter particles is rather challenging. Recently, a few groups have identified a tentative 130 GeV line signal in the Galactic center, which could be interpreted as the signal of dark matter annihilation. Using current 130 GeV line data and adopting the generalized Navarro-Frenk-White profile of the dark matter halo-local dark matter density {rho}{sub 0} = 0.4 GeV cm{sup -3} and r{sub s} = 20 kpc-we obtain a 95% confidence level lower (upper) limit on the inner slope of dark matter density distribution, {alpha} = 1.06 (the cross section of dark matter annihilation into {gamma}-rays ({sigma}v){sub {chi}{chi}{sub {yields}{sub {gamma}{gamma}}}} = 1.3 Multiplication-Sign 10{sup -27} cm{sup 3} s{sup -1}). Such a slope is consistent with the results of some N-body simulations and, if the signal is due to dark matter, suggests that baryonic processes may be unimportant.

Yang Ruizhi; Feng Lei; Li Xiang; Fan Yizhong, E-mail: yzfan@pmo.ac.cn [Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China)

2013-06-20T23:59:59.000Z

386

Experimental concept and design of DarkLight, a search for a heavy photon  

SciTech Connect

This talk gives an overview of the DarkLight experimental concept: a search for a heavy photon A′ in the 10-90 MeV/c 2 mass range. After briefly describing the theoretical motivation, the talk focuses on the experimental concept and design. Topics include operation using a half-megawatt, 100 MeV electron beam at the Jefferson Lab FEL, detector design and performance, and expected backgrounds estimated from beam tests and Monte Carlo simulations.

Cowan, Ray F. [MIT

2013-11-01T23:59:59.000Z

387

The Process of Generation of Mass, The Higgs Boson, and Dark Matter  

E-Print Network (OSTI)

A dynamical mechanism of symmetry breaking in which gauge and matter fields play an active role is proposed. It basically represents a covariant generalization of the mechanism responsible for superconductivity, and provides a {\\em natural} mechanism of generation of mass which is not in conflict with the present value of the cosmological constant. When applied to SU(2)$\\times$U(1) leads to exactly the same physics (Lagrangian density) as the Standard Model but modifying {\\em only} the Higgs sector. It also predicts the appearance over all space of a classical scalar field as well as the existence of density fluctuations. According to it, space would be filled with a macroscopically large number of Higgs bosons which now appear as light, stable scalar particles {\\em decoupled} from ordinary matter and radiation. Therefore they would play the same role as the Cooper pairs in superconductivity and would be a natural candidate for dark matter.

V. Delgado

1993-05-11T23:59:59.000Z

388

A New Dark Matter Model for Galaxies RHCPP00-1T astro-ph/0002391  

E-Print Network (OSTI)

In this paper a new theory of Dark Matter is proposed. Experimental analysis of several Galaxies show how the non-gravitational contribution to galactic Velocity Rotation Curves can be interpreted as that due to the Cosmological Constant ?. The experimentally determined values for ? are found to be consistent with those expected from Cosmological Constraints. The Cosmological Constant is interpreted as leading to a constant energy density which in turn can be used to partly address the energy deficit problem (Dark Energy) of the Universe. The work presented here leads to the conclusion that the Cosmological Constant is negative and that the universe is de-accelerating. This is in clear contradiction to the Type Ia Supernovae results which support an accelerating universe.

George V. Kraniotis; Steven B. Whitehouse

2000-01-01T23:59:59.000Z

389

CONSTRAINTS ON THE SHAPE OF THE MILKY WAY DARK MATTER HALO FROM THE SAGITTARIUS STREAM  

SciTech Connect

We propose a new model for the dark matter halo of the Milky Way that fits the properties of the stellar stream associated with the Sagittarius dwarf galaxy. Our dark halo is oblate with q{sub z} = 0.9 for r {approx}< 10 kpc, and can be made to follow the Law and Majewski model at larger radii. However, we find that the dynamical perturbations induced by the Large Magellanic Cloud on the orbit of Sgr cannot be neglected when modeling its streams. When taken into account, this leads us to constrain the Galaxy's outer halo shape to have minor-to-major axis ratio >(c/a){sub {Phi}} = 0.8 and intermediate-to-major axis ratio (b/a){sub {Phi}} = 0.9, in good agreement with cosmological expectations.

Vera-Ciro, Carlos [Department of Astronomy, University of Wisconsin, 2535 Sterling Hall, 475 N. Charter Street, Madison, WI 53076 (United States); Helmi, Amina, E-mail: ciro@astro.wisc.edu [Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800, 9700 AV Groningen (Netherlands)

2013-08-10T23:59:59.000Z

390

Constraining dark matter late-time energy injection: decays and p-wave annihilations  

E-Print Network (OSTI)

We use the latest cosmic microwave background (CMB) observations to provide updated constraints on the dark matter lifetime as well as on p-wave suppressed annihilation cross sections in the 1 MeV to 1 TeV mass range. In contrast to scenarios with an s-wave dominated annihilation cross section, which mainly affect the CMB close to the last scattering surface, signatures associated with these scenarios essentially appear at low redshifts (z well as Lyman-alpha measurements of the matter temperature at z ~ 4 to set a 95% confidence level lower bound on the dark matter lifetime of ~ 4 x 10^25 s for m_chi = 100 MeV. This bound becomes lower by two orders of magnitude at m_chi = 1 TeV due to inefficient energy deposition into the intergalactic medium. We also show that structure formation can enhance the effect of p-wave suppressed annihilation cross sections by many orders of magnitude with respect to the background cosmological rate, although even with this enhancement, CMB constraints are not yet strong enough to reach the thermal relic value of the cross section.

Roberta Diamanti; Laura Lopez-Honorez; Olga Mena; Sergio Palomares-Ruiz; Aaron C. Vincent

2013-08-12T23:59:59.000Z

391

{lambda}{alpha}DM: Observational constraints on unified dark matter with constant speed of sound  

SciTech Connect

We consider the hypothesis that dark energy and dark matter are the two faces of a single dark component, a unified dark matter (UDM) that we assume can be modeled by the affine equation of state (EoS) P=p{sub 0}+{alpha}{rho}, resulting in an effective cosmological constant {rho}{sub {lambda}}=-p{sub 0}/(1+{alpha}). The affine EoS arises from the simple assumption that the speed of sound is constant; it may be seen as an approximation to an unknown barotropic EoS P=P({rho}), and may as well represent the tracking solution for the dynamics of a scalar field with appropriate potential. Furthermore, in principle the affine EoS allows the UDM to be phantom. We constrain the parameters of the model, {alpha} and {omega}{sub {lambda}}, using data from a suite of different cosmological observations, and perform a comparison with the standard {lambda}CDM model, containing both cold dark matter and a cosmological constant. First considering a flat cosmology, we find that the UDM model with affine EoS fits the joint observations very well, better than {lambda}CDM, with best-fit values {alpha}=0.01{+-}0.02 and {omega}{sub {lambda}}=0.70{+-}0.04 (95% confidence intervals). The standard model (best-fit {omega}{sub {lambda}}=0.71{+-}0.04), having one less parameter, is preferred by a Bayesian model comparison. However, the affine EoS is at least as good as the standard model if a flat curvature is not assumed as a prior for {lambda}CDM. For the latter, the best-fit values are {omega}{sub K}=-0.02{sub -0.02}{sup +0.01} and {omega}{sub {lambda}}=0.71{+-}0.04, i.e. a closed model is preferred. A phantom UDM with affine EoS is ruled out well beyond 3{sigma}.

Balbi, Amedeo [Dipartimento di Fisica, Universita di Roma 'Tor Vergata', via della Ricerca Scientifica 1, 00133 Rome (Italy); INFN Sezione di Roma 'Tor Vergata', via della Ricerca Scientifica 1, 00133 Rome (Italy); Bruni, Marco [Dipartimento di Fisica, Universita di Roma 'Tor Vergata', via della Ricerca Scientifica 1, 00133 Rome (Italy); INFN Sezione di Roma 'Tor Vergata', via della Ricerca Scientifica 1, 00133 Rome (Italy); Institute of Cosmology and Gravitation, University of Portsmouth, Mercantile House, Portsmouth PO1 2EG (United Kingdom); Quercellini, Claudia [Dipartimento di Fisica, Universita di Roma 'Tor Vergata', via della Ricerca Scientifica 1, 00133 Rome (Italy)

2007-11-15T23:59:59.000Z

392

Marriage ŕ-la-MOND: Baryonic dark matter in galaxy clusters and the cooling flow puzzle  

E-Print Network (OSTI)

I start with a brief introduction to MOND phenomenology and its possible roots in cosmology--a notion that may turn out to be the most far reaching aspect of MOND. Next I discuss the implications of MOND for the dark matter (DM) doctrine: MOND's successes imply that baryons determine everything. For DM this would mean that the puny tail of leftover baryons in galaxies wags the hefty DM dog. This has to occur in many intricate ways, and despite the haphazard construction history of galaxies--a very tall order. I then concentrate on galaxy clusters in light of MOND, which still requires some yet undetected cluster dark matter, presumably in some baryonic form (CBDM). This CBDM might contribute to the heating of the x-ray emitting gas and thus alleviate the cooling-flow puzzle. MOND, qua theory of dynamics, does not directly enter the microphysics of the gas; however, it does force a new outlook on the role of DM in shaping the cluster gasdynamics: MOND tells us that the cluster DM is not cold dark matter, is not so abundant, and is not expected in galaxies; it is thus not subject to constraints on baryonic DM in galaxies. The mass in CBDM required in a whole cluster is, typically, similar to that in hot gas, but is rather more centrally concentrated, totally dominating the core. The CBDM contribution to the baryon budget in the universe is thus small. Its properties, deduced for isolated clusters, are consistent with the observations of the ``bullet cluster''. Its kinetic-energy reservoir is much larger than that of the hot gas in the core, and would suffice to keep the gas hot for many cooling times. Heating can be effected in various ways depending on the exact nature of the CBDM, from very massive black holes to cool, compact gas clouds.

Mordehai Milgrom

2007-12-27T23:59:59.000Z

393

Abstract Nuclear Instruments and Methods in Physics Research A 559 (2006) 411–413 The SuperCDMS proposal for dark matter detection  

E-Print Network (OSTI)

Presently the CDMS-II collaboration’s Weakly Interacting Massive Particle (WIMP) search at the Soudan Underground Laboratory sets the most stringent exclusion limits of any WIMP cold dark matter direct-detection experiment. To extend our reach further, to WIMP-nucleon cross-sections in the range 10 46 10 44 cm2, we propose SuperCDMS, which would take advantage of a very deep site. One promising site is the recently approved SNOLab facility in Canada. In this paper we will present our overall program and focus on

D. S. Akerib A; M. J. Attisha B; C. N. Bailey A; L. Baudis C; D. A. Bauer D; J. Cooley E; M. B. Crisler D; P. Cushman G; P. Denes H; M. R. Dragowsky A; L. Duong G; D. Holmgren D; M. E. Huber K; K. D. Irwin L; A. Lu H; R. Mahapatra F; P. Meunier I; N. Mirabolfathi I; H. Nelson F; R. W. Ogburn E; E. Ramberg D; A. Reisetter G; T. Saab C; B. Sadoulet H; Er F; D. N. Seitz I; B. Serfass I; R. W. Schnee A; K. M. Sundqvist I; J. -p. F. Thompson B; S. Yellin F; J. Yoo D; B. A. Young M

2005-01-01T23:59:59.000Z

394

Thermal decoupling and the smallest subhalo mass in dark matter models with Sommerfeld-enhanced annihilation rates  

E-Print Network (OSTI)

We consider dark matter consisting of weakly interacting massive particles (WIMPs) and revisit in detail its thermal evolution in the early universe, with a particular focus on models where the annihilation rate is enhanced by the Sommerfeld effect. After chemical decoupling, or freeze-out, dark matter no longer annihilates but is still kept in local thermal equilibrium due to scattering events with the much more abundant standard model particles. During kinetic decoupling, even these processes stop to be effective, which eventually sets the scale for a small-scale cutoff in the matter density fluctuations. Afterwards, the WIMP temperature decreases more quickly than the heat bath temperature, which causes dark matter to reenter an era of annihilation if the cross-section is enhanced by the Sommerfeld effect. Here, we give a detailed and self-consistent description of these effects. As an application, we consider the phenomenology of simple leptophilic models that have been discussed in the literature and fin...

Aarssen, Laura G van den; Goedecke, Yasar C

2012-01-01T23:59:59.000Z

395

What are Machos? Limits on Stellar Objects as the Dark Matter of our Halo  

E-Print Network (OSTI)

The nature of the Massive Compact Halo objects seen in microlensing experiments and interpreted as dark matter in the Halo of our Galaxy remains a mystery. Arguments are presented that these events are probably not ordinary stellar or substellar objects, i.e., they are probably not faint stars, brown dwarfs, white dwarfs, or neutron stars. On theoretical grounds one is then pushed to either exotic explanations or a "no-Macho" Halo (in which the Machos reside elsewhere than in the Halo). Indeed a nonbaryonic component in the Halo seems to be required.

Katherine Freese; Brian Fields; David Graff

1999-01-13T23:59:59.000Z

396

Nuclear recoil energy scale in liquid xenon with application to the direct detection of dark matter  

SciTech Connect

We show for the first time that the quenching of electronic excitation from nuclear recoils in liquid xenon is well-described by Lindhard theory, if the nuclear recoil energy is reconstructed using the combined (scintillation and ionization) energy scale proposed by Shutt et al.. We argue for the adoption of this perspective in favor of the existing preference for reconstructing nuclear recoil energy solely from primary scintillation. We show that signal partitioning into scintillation and ionization is well-described by the Thomas-Imel box model. We discuss the implications for liquid xenon detectors aimed at the direct detection of dark matter.

Sorensen, P; Dahl, C E

2011-02-14T23:59:59.000Z

397

Gauge-Higgs Unification: Stable Higgs Bosons as Cold Dark Matter  

E-Print Network (OSTI)

In the gauge-Higgs unification the 4D Higgs field becomes a part of the extra-dimensional component of the gauge potentials. In the $SO(5) \\times U(1)$ gauge-Higgs unification in the Randall-Sundrum warped spacetime the electroweak symmetry is dynamically broken through the Hosotani mechanism. The Higgs bosons become absolutely stable, and become the dark matter of the universe. The mass of the Higgs boson is determined from the WMAP data to be about 70 GeV.

Yutaka Hosotani

2010-03-16T23:59:59.000Z

398

From the Cosmological Constant: Higgs Boson, Dark Matter, and Quantum Gravity Scales  

E-Print Network (OSTI)

We suggest discovery targets for the Higgs boson, dark matter, and quantum gravity mass scales, motivated by the Dirac equation for the electron in deSitter space, and a sixth-order constraint between the electron QED parameters and the cosmological constant. We go on to show that this constraint can be viewed as a structural parameter of the electron, and leads naturally to a new cosmic horizon. A dual fourth-order constraint implies a second-order one, from which the electron neutrino mass is derived.

James R. Bogan

2009-02-16T23:59:59.000Z

399

SHORT GAMMA-RAY BURSTS AND DARK MATTER SEEDING IN NEUTRON STARS  

SciTech Connect

We present a mechanism based on internal self-annihilation of dark matter accreted from the galactic halo in the inner regions of neutron stars that may trigger full or partial conversion into a quark star. We explain how this effect may induce a gamma-ray burst (GRB) that could be classified as short, according to the usual definition based on time duration of the prompt gamma-ray emission. This mechanism differs in many aspects from the most discussed scenario associating short GRBs with compact object binary mergers. We list possible observational signatures that should help distinguish between these two possible classes of progenitors.

Perez-Garcia, M. Angeles [Department of Fundamental Physics and IUFFyM, University of Salamanca, Plaza de la Merced s/n, E-37008 Salamanca (Spain); Daigne, F.; Silk, J., E-mail: mperezga@usal.es, E-mail: daigne@iap.fr, E-mail: j.silk1@physics.ox.ac.uk [UPMC-CNRS, UMR7095, Institut d'Astrophysique de Paris, F-75014 Paris (France)

2013-05-10T23:59:59.000Z

400

Evidence for Hydro-Gravitational Structure Formation Theory versus Cold-Dark-Matter, Hierarchical-Clustering, and Jeans 1902  

E-Print Network (OSTI)

Observations are compared to conflicting predictions about self-gravitational structure formation by the hydro-gravitational theory (HGT) of Gibson 1996-2003 versus cold-dark-matter hierarchical-clustering-cosmology (CDMHCC) and the Jeans 1902 criterion. According to HGT, gravitational structures form immediately after mass-energy equality by plasma fragmentation at 30,000 years when viscous and weak turbulence forces first balance gravitational forces within the horizon L_H = ct < L_J = c/[3\\rho G]^1/2, contrary to the Jeans 1902 criterion. Buoyancy forces fossilize the 10^-12 s^-1 rate-of-strain and the 10^-17 kg m^-3 baryonic density. The non-baryonic dark matter (NBDM) diffuses into the voids rather than forming cold-dark-matter (CDM) halos required by CDMHCC. From HGT, supercluster-mass to galaxy-mass fragments exist at the plasma to gas transition, and these fragment further to form proto-globular-star clusters (PGCs) and planetary-mass primordial-fog-particles (PFPs): the baryonic dark matter of the interstellar-medium and inner-galaxy-dark-matter-halos, from which all planets and stars are formed by accretion (Gibson 1996, Schild 1996). From HGT and a rich cluster mass profile (Tyson and Fischer 1995), D_NBDM = 6 x10^28 m^2 s^-1, m_NBDM <= 10^-33 kg, and the NBDM forms outer-galaxy halos after 300,000 years.

Carl H. Gibson; Rudy Schild

2003-04-27T23:59:59.000Z

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401

Conversion of Dark matter axions to photons in magnetospheres of neutron stars  

E-Print Network (OSTI)

We propose a new method to detect observational appearance of Dark Matter axions. The method utilizes observations of neutron stars (NSs) in radio. It is based on the conversion of axions to photons in strong magnetic fields of NSs (Primakoff effect). Whether the conversion takes place, the radio spectrum of the object would have a very distinctive feature -- a narrow spike at a frequency corresponding to the rest mass of the axion. For example, if the coupling constant of the photon-axion interaction is $M=10^{10}$ GeV, the density of Dark Matter axions is $\\rho=10^{-24} {\\rm g cm^{-3}}$, and the axion mass is $5 {\\rm \\mu eV}$, then a flux from a strongly magnetized ($10^{14}$ G) NS at the distance 300 pc from the Sun is expected to be about few tenths of mJy at the frequency $\\approx 1200$ MHz in the bandwidth $\\approx 3$ MHz. Close-by X-ray dim isolated neutron stars are proposed as good candidates to look for such radio emission.

M. S. Pshirkov; S. B. Popov

2007-11-08T23:59:59.000Z

402

MeV dark matter in the 3+1+1 model  

E-Print Network (OSTI)

The existence of light sterile neutrinos in the eV mass range with relatively large mixing angles with the active neutrinos has been proposed for a variety of reasons, including to improve the fit to the LSND and MiniBooNE neutrino oscillation experiments, and reactor disappearance experiments. In ref. Phys. Rev. D 84, 053001 (2011), it was shown that neutrino mixing with a heavier sterile neutrino, in the mass range between 33 eV and several GeV, could significantly affect and improve the agreement between neutrino oscillation models with light sterile neutrinos and short baseline experimental results, allowing for a new source of CP violation in appearance experiments and for different apparent mixing angles in appearance and disappearance experiments. However in refs. Phys. Rev. D 86, 033015 (2012) and JHEP 1204, 083 (2012) it was shown that various collider experiment, supernovae, and cosmological constraints can eliminate most of the parameter region where such a heavy sterile neutrino can have a significant effect on neutrino oscillations. In this paper we consider the effects of allowing a new light scalar in the MeV mass region, which is a potential dark matter candidate, to interact with the sterile neutrinos, and show that the resulting model is a consistent theory of neutrino oscillation anomalies and dark matter which can also potentially explain the INTEGRAL excess of 511 keV gamma rays in the central region of the galaxy.

Jinrui Huang; Ann E Nelson

2013-06-25T23:59:59.000Z

403

The High Energy Gamma-Ray Background as a Probe of the Dark Matter in the Galactic Halo  

E-Print Network (OSTI)

We present constraints on the density of halo dark matter candidates within the solar circle based on the anisotropy in the high energy gamma-ray background. The known galactic components of the gamma-ray background, in particular the inverse Compton component, have been estimated more accurately. We find the spectrum of the residual emission, after subtracting the galactic component is inconsistent with emission from some of the proposed dark matter candidates. We derive upper limits of 10^8 M_sun for the mass of diffuse gas and 3*10^9 pc^(-3) for the number density of primordial black holes contributing to the gamma-ray background.

R. Chary; E. L. Wright

1998-11-20T23:59:59.000Z

404

Cold Dark Matter Substructure and Galactic Disks I: Morphological Signatures of Hierarchical Satellite Accretion  

E-Print Network (OSTI)

(Abridged) We conduct a series of high-resolution, dissipationless N-body simulations to investigate the cumulative effect of substructure mergers onto thin disk galaxies in the context of the LCDM paradigm of structure formation. Our simulation campaign is based on a hybrid approach. Substructure properties are culled directly from cosmological simulations of galaxy-sized cold dark matter (CDM) halos. In contrast to what can be inferred from statistics of the present-day substructure populations, accretions of massive subhalos onto the central regions of host halos, where the galactic disk resides, since z~1 should be common occurrences. One host halo merger history is subsequently used to seed controlled numerical experiments of repeated satellite impacts on an initially-thin Milky Way-type disk galaxy. We show that these accretion events produce several distinctive observational signatures in the stellar disk including: a ring-like feature in the outskirts; a significant flare; a central bar; and faint fil...

Kazantzidis, Stelios; Zentner, Andrew R; Kravtsov, Andrey V; Moustakas, Leonidas A

2007-01-01T23:59:59.000Z

405

On prospects for dark matter indirect detection in the Constrained MSSM  

E-Print Network (OSTI)

In the framework of the Constrained MSSM we derive the most probable ranges of the diffuse gamma radiation flux from the direction of the Galactic center and of the positron flux from the Galactic halo due to neutralino dark matter annihilation. We find that, for a given halo model, and assuming flat priors, the 68% probability range of the integrated gamma-ray flux spans about one order of magnitude, while the 95% probability range can be much larger and extend over four orders of magnitude (even exceeding five for a tiny region at small neutralino mass). The detectability of the signal by GLAST depending primarily on the cuspiness of the halo profile. The positron flux, on the other hand, appears to be too small to be detectable by PAMELA, unless the boost factor is at least of order ten and/or the halo profile is extremely cuspy. We also briefly discuss the sensitivity of our results to the choice of priors.

Leszek Roszkowski; Roberto Ruiz de Austri; Joe Silk; Roberto Trotta

2007-07-04T23:59:59.000Z

406

Ionization Yield from Nuclear Recoils in Liquid-Xenon Dark Matter Detection  

E-Print Network (OSTI)

The ionization yield in the two-phase liquid xenon dark-matter detector has been studied in keV nuclear-recoil energy region. The newly-obtained nuclear quenching as well as the recently-measured average energy required to produce an electron-ion pair are used to calculate the total electric charges produced. To estimate the fraction of the electron charges collected, the Thomas-Imel model is generalized to describing the field dependence for nuclear recoils in liquid xenon. With free parameters fitted to experiment measured 56.5 keV nuclear recoils, the energy dependence of ionization yield for nuclear recoils is predicted, which increases with the decreasing of the recoiling energy and reaches the maximum value at 2~3 keV. This prediction agrees well with existing data and may help to lower the energy detection threshold for nuclear recoils to ~1 keV.

Mu, Wei

2013-01-01T23:59:59.000Z

407

Information content in the halo-model dark-matter power spectrum  

E-Print Network (OSTI)

Using the halo model, we investigate the cosmological Fisher information in the non-linear dark-matter power spectrum about the initial amplitude of linear power. We find that there is little information on `translinear' scales (where the one- and two-halo terms are both significant) beyond what is on linear scales, but that additional information is present on small scales, where the one-halo term dominates. This behavior agrees with the surprising results that Rimes & Hamilton (2005, 2006) found using N-body simulations. We argue that the translinear plateau in cumulative information arises largely from fluctuations in the numbers of large haloes in a finite volume. This implies that more information could be extracted on non-linear scales if the masses of the largest haloes in a survey are known.

Mark C. Neyrinck; István Szapudi; Christopher D. Rimes

2006-04-13T23:59:59.000Z

408

Galaxy Bulge Formation: Interplay with Dark Matter Halo and Central Supermassive Black Hole  

E-Print Network (OSTI)

We present a simple scenario where the formation of galactic bulges was regulated by the dark halo gravity and regulated the growth of the central supermassive black hole. Assuming the angular momentum is low, we suggest that bulges form in a runaway collapse due to the "gravothermal" instability once the central gas density or pressure exceeds certain threshold (Xu & Zhao 2007). We emphasize that the threshold is nearly universal, set by the background NFW dark matter gravity $g_{DM} \\sim 1.2 \\times 10^{-8}{\\rm cm} {\\rm sec}^{-2}$ in the central cusps of halos. Unlike known thresholds for gradual formation of galaxy disks, we show that the universal "halo-regulated" star formation threshold for spheroids matches the very high star formation rate and star formation efficiency shown in high-redshift observations of central starburst regions. The starburst feedback also builds up a pressure shortly after the collapse. This large pressure could both act outward to halt further infall of gas from larger scale, and act inward to counter the Compton-thick wind launched from the central black hole in an Eddington accretion. Assuming the feedback balancing inward and outward forces, our scenario naturally gives rise to the black hole-bulge relationships observed in the local universe.

Bing-Xiao Xu; Xue-Bing Wu; HongSheng Zhao

2007-01-29T23:59:59.000Z

409

EVIDENCE FOR A TRIAXIAL MILKY WAY DARK MATTER HALO FROM THE SAGITTARIUS STELLAR TIDAL STREAM  

Science Conference Proceedings (OSTI)

Observations of the lengthy tidal streams produced by the destruction of the Sagittarius dwarf spheroidal (Sgr dSph) are capable of providing strong constraints on the shape of the Galactic gravitational potential. However, previous work, based on modeling different stream properties in axisymmetric Galactic models, has yielded conflicting results: while the angular precession of the Sgr leading arm is most consistent with a spherical or slightly oblate halo, the radial velocities of stars in this arm are reproduced only by prolate halo models. We demonstrate that this apparent paradox can be resolved by instead adopting a triaxial potential. Our new Galactic halo model, which simultaneously fits all well-established phase space constraints from the Sgr stream, provides the first conclusive evidence for, and tentative measurement of, triaxiality in an individual dark matter halo. The Milky Way halo within {approx}60 kpc is best characterized by a minor/major axis ratio of the isovelocity contours c/a {approx} 0.67, intermediate/major axis ratio b/a {approx} 0.83, and triaxiality parameter T {approx} 0.56. In this model, the minor axis of the dark halo is coincident with the Galactic X-axis connecting the Sun and the Galactic center to within {approx}15 deg., while the major axis also lies in the Galactic plane, approximately along the Galactic Y-axis.

Law, David R. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States); Majewski, Steven R. [Department of Astronomy, University of Virginia, Charlottesville, VA 22904-0818 (United States); Johnston, Kathryn V., E-mail: drlaw@astro.ucla.ed, E-mail: srm4n@virginia.ed, E-mail: kvj@astro.columbia.ed [Department of Astronomy, Columbia University, New York, NY 10027 (United States)

2009-09-20T23:59:59.000Z

410

Supersymmetric Benchmarks with Non-Universal Scalar Masses or Gravitino Dark Matter  

E-Print Network (OSTI)

We propose and examine a new set of benchmark supersymmetric scenarios, some of which have non-universal Higgs scalar masses (NUHM) and others have gravitino dark matter (GDM). The scalar masses in these models are either considerably larger or smaller than the narrow range allowed for the same gaugino mass m_{1/2} in the constrained MSSM (CMSSM) with universal scalar masses m_0 and neutralino dark matter. The NUHM and GDM models with larger m_0 may have large branching ratios for Higgs and/or $Z$ production in the cascade decays of heavier sparticles, whose detection we discuss. The phenomenology of the GDM models depends on the nature of the next-to-lightest supersymmetric particle (NLSP), which has a lifetime exceeding 10^4 seconds in the proposed benchmark scenarios. In one GDM scenario the NLSP is the lightest neutralino \\chi, and the supersymmetric collider signatures are similar to those in previous CMSSM benchmarks, but with a distinctive spectrum. In the other GDM scenarios based on minimal supergravity (mSUGRA), the NLSP is the lighter stau slepton {\\tilde \\tau}_1, with a lifetime between ~ 10^4 and 3 X 10^6 seconds. Every supersymmetric cascade would end in a {\\tilde \\tau}_1, which would have a distinctive time-of-flight signature. Slow-moving {\\tilde \\tau}_1's might be trapped in a collider detector or outside it, and the preferred detection strategy would depend on the {\\tilde \\tau}_1 lifetime. We discuss the extent to which these mSUGRA GDM scenarios could be distinguished from gauge-mediated models.

A. De Roeck; J. Ellis; F. Gianotti; F. Moortgat; K. A. Olive; L. Pape

2005-08-18T23:59:59.000Z

411

Bounds on Dark Matter Properties from Radio Observations of Ursa Major II using the Green Bank Telescope  

E-Print Network (OSTI)

Radio observations of the Ursa Major II dwarf spheroidal galaxy obtained using the Green Bank Telescope are used to place bounds on WIMP dark matter properties. Dark matter annihilation releases energy in the form of charged particles which emit synchrotron radiation in the magnetic field of the dwarf galaxy. We compute the expected synchrotron radiation intensity from WIMP annihilation to various primary channels. The predicted synchrotron radiation is sensitive to the distribution of dark matter in the halo, the diffusion coefficient D_0, the magnetic field strength B, the particle mass m_\\chi, the annihilation rate , and the annihilation channel. Limits on , m_\\chi, B, and D_0 are obtained for the e^+ e^-, \\mu^+ \\mu^-, \\tau^+ \\tau^-, and b \\bar b channels. Constraints on these parameters are sensitive to uncertainties in the measurement of the dark matter density profile. For the best fit halo parameters derived from stellar kinematics, we exclude 10 GeV WIMPs annihilating directly to e^+ e^- at the thermal rate = 2.18 x 10^{-26} cm^3/s at the 2\\sigma level, for B > 0.6 microGauss (1.6 microGauss) and D_0 = 0.1 (1.0) x the Milky Way diffusion value.

Aravind Natarajan; Jeffrey B. Peterson; Tabitha C. Voytek; Kristine Spekkens; Brian Mason; James Aguirre; Beth Willman

2013-08-22T23:59:59.000Z

412

A Cosmological Kinetic Theory for the Evolution of Cold Dark Matter Halos with Substructure: Quasi-Linear Theory  

E-Print Network (OSTI)

We present a kinetic theory for the evolution of the phase-space distribution of dark matter particles in galaxy halos in the presence of a cosmological spectrum of fluctuations. This theory introduces a new way to model the formation and evolution of halos, which traditionally have been investigated by analytic gravitational infall models or numerical N-body methods. Unlike the collisionless Boltzmann equation, our kinetic equation contains nonzero terms on the right-hand side arising from stochastic fluctuations in the gravitational potential due to substructures in the dark matter mass distribution. Using statistics for constrained Gaussian random fields in standard cosmological models, we show that our kinetic equation to second-order in perturbation theory is of the Fokker-Planck form, with one scattering term representing drift and the other representing diffusion in velocity-space. The drift is radial, and the drift and diffusion coefficients depend only on positions and not velocities; our relaxation process in the quasilinear regime is therefore different from the standard two-body relaxation. We provide explicit expressions relating these coefficients to the linear power spectrum of mass fluctuation and present results for the currently favored cold dark matter model with a nonzero cosmological constant. Solutions to this kinetic equation will provide a complete description of the cold dark matter spatial and velocity distributions for the average halo during the early phases of galaxy halo formation.

Chung-Pei Ma; Edmund Bertschinger

2003-11-03T23:59:59.000Z

413

Measuring the Dark Matter Halo Mass of X-ray AGN at z~1 using photometric redshifts  

E-Print Network (OSTI)

Data from the AEGIS, COSMOS and ECDFS surveys are combined to infer the bias and dark matter halo mass of moderate luminosity [LX(2-10 keV) = 42.9 erg s-1] X-ray AGN at z~1 via their cross-correlation function with galaxies. In contrast to standard cross-correlation function estimators, we present a method that requires spectroscopy only for the AGN and uses photometric redshift probability distribution functions for galaxies to determine the projected real-space AGN/galaxy cross-correlation function. The estimated dark matter halo mass of X-ray AGN in the combined AEGIS, COSMOS and ECDFS fields is ~13h-1M_solar, in agreement with previous studies at similar redshift and luminosity ranges. Removing from the sample the 5 per cent of the AGN associated with X-ray selected groups results in a reduction by about 0.5 dex in the inferred AGN dark matter halo mass. The distribution of AGN in dark matter halo mass is therefore skewed and the bulk of the population lives in moderate mass haloes. This result favour col...

Mountrichas, G; Finoguenov, A; Erfanianfar, G; Cooper, M C; Coil, A L; Laird, E S; Nandra, K; Newman, J A

2012-01-01T23:59:59.000Z

414

Photo Credit: Peter GinterSLAC National Accelerator Laboratory Dark Energy  

E-Print Network (OSTI)

Photo Credit: Peter GinterSLAC National Accelerator Laboratory #12;Dark Energy 70% Dark Matter 26 and Advanced Camera for Surveys #12;Dark Energy 70% Dark Matter 26% Ordinary Matter 4% #12;Dark Energy 70% Dark Matter 26% Ordinary Matter 4% #12;Dark Energy 70% Dark Matter 26% Ordinary Matter 4% #12;Dark Energy 70

Osheroff, Douglas D.

415

The virial theorem and the dark matter problem in hybrid metric-Palatini gravity  

E-Print Network (OSTI)

Hybrid metric-Palatini gravity is a recently proposed theory, consisting of the superposition of the metric Einstein-Hilbert Lagrangian with an $f(\\cal R)$ term constructed \\`{a} la Palatini. The theory predicts the existence of a long-range scalar field, which passes the Solar System observational constraints, even if the scalar field is very light, and modifies the cosmological and galactic dynamics. Thus, the theory opens new possibilities to approach, in the same theoretical framework, the problems of both dark energy and dark matter. In this work, we consider the generalized virial theorem in the scalar-tensor representation of the hybrid metric-Palatini gravity. More specifically, taking into account the relativistic collisionless Boltzmann equation, we show that the supplementary geometric terms in the gravitational field equations provide an effective contribution to the gravitational potential energy. We show that the total virial mass is proportional to the effective mass associated with the new terms generated by the effective scalar field, and the baryonic mass. This shows that the geometric origin in the generalized virial theorem may account for the well-known virial theorem mass discrepancy in clusters of galaxies. In addition to this, we also consider astrophysical applications of the model and show that the model predicts that the mass associated to the scalar field and its effects extend beyond the virial radius of the clusters of galaxies. In the context of the galaxy cluster velocity dispersion profiles predicted by the hybrid metric-Palatini model, the generalized virial theorem can be an efficient tool in observationally testing the viability of this class of generalized gravity models.

Salvatore Capozziello; Tiberiu Harko; Tomi S. Koivisto; Francisco S. N. Lobo; Gonzalo J. Olmo

2012-12-23T23:59:59.000Z

416

ICE AND DUST IN THE PRESTELLAR DARK CLOUD LYNDS 183: PREPLANETARY MATTER AT THE LOWEST TEMPERATURES  

Science Conference Proceedings (OSTI)

Dust grains are nucleation centers and catalysts for the growth of icy mantles in quiescent interstellar clouds, the products of which may accumulate into preplanetary matter when new stars and solar systems form within the clouds. In this paper, we present the first spectroscopic detections of silicate dust and the molecular ices H{sub 2}O, CO, and CO{sub 2} in the vicinity of the prestellar core L183 (L134N). An infrared photometric survey of the cloud was used to identify reddened background stars, and we present spectra covering solid-state absorption features in the wavelength range 2-20 {mu}m for nine of them. The mean composition of the ices in the best-studied line of sight (toward J15542044-0254073) is H{sub 2}O:CO:CO{sub 2} Almost-Equal-To 100:40:24. The ices are amorphous in structure, indicating that they have been maintained at low temperature ({approx}ice column density N(H{sub 2}O) correlates with reddening by dust, exhibiting a threshold effect that corresponds to the transition from unmantled grains in the outer layers of the cloud to ice-mantled grains within, analogous to that observed in other dark clouds. A comparison of results for L183 and the Taurus and IC 5146 dark clouds suggests common behavior, with mantles first appearing in each case at a dust column corresponding to a peak optical depth {tau}{sub 9.7} = 0.15 {+-} 0.03 in the silicate feature. Our results support a previous conclusion that the color excess E{sub J-K} does not obey a simple linear correlation with the total dust column in lines of sight that intercept dense clouds. The most likely explanation is a systematic change in the optical properties of the dust as the density increases.

Whittet, D. C. B.; Poteet, C. A.; Bajaj, V. M.; Horne, D. [Department of Physics, Applied Physics and Astronomy and New York Center for Astrobiology, Rensselaer Polytechnic Institute, 110 Eighth Street, Troy, NY 12180 (United States); Chiar, J. E. [SETI Institute, Carl Sagan Center, 189 Bernardo Avenue, Mountain View, CA 94043 (United States); Pagani, L. [LERMA, UMR 8112 du CNRS, Observatoire de Paris, 61 Av. de l'Observatoire, F-75014 Paris (France); Shenoy, S. S. [SOFIA Science Center, NASA Ames Research Center, MS 232-12, Moffett Field, CA 94035 (United States); Adamson, A. J. [Gemini Observatory, Southern Operations Center, Casilla 603, La Serena (Chile)

2013-09-10T23:59:59.000Z

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Thermal decoupling and the smallest subhalo mass in dark matter models with Sommerfeld-enhanced annihilation rates  

E-Print Network (OSTI)

We consider dark matter consisting of weakly interacting massive particles (WIMPs) and revisit in detail its thermal evolution in the early universe, with a particular focus on models where the annihilation rate is enhanced by the Sommerfeld effect. After chemical decoupling, or freeze-out, dark matter no longer annihilates but is still kept in local thermal equilibrium due to scattering events with the much more abundant standard model particles. During kinetic decoupling, even these processes stop to be effective, which eventually sets the scale for a small-scale cutoff in the matter density fluctuations. Afterwards, the WIMP temperature decreases more quickly than the heat bath temperature, which causes dark matter to reenter an era of annihilation if the cross-section is enhanced by the Sommerfeld effect. Here, we give a detailed and self-consistent description of these effects. As an application, we consider the phenomenology of simple leptophilic models that have been discussed in the literature and find that the relic abundance can be affected by as much two orders of magnitude or more. We also compute the mass of the smallest dark matter subhalos in these models and find it to be in the range of about 10^{-10} to 10 solar masses; even much larger cutoff values are possible if the WIMPs couple to force carriers ligh