HUNTING THE QUARK GLUON PLASMA.
LUDLAM, T.; ARONSON, S.
2005-04-11
The U.S. Department of Energy's Relativistic Heavy Ion Collider (RHIC) construction project was completed at BNL in 1999, with the first data-taking runs in the summer of 2000. Since then the early measurements at RHIC have yielded a wealth of data, from four independent detectors, each with its international collaboration of scientists: BRAHMS, PHENIX, PHOBOS, and STAR [1]. For the first time, collisions of heavy nuclei have been carried out at colliding-beam energies that have previously been accessible only for high-energy physics experiments with collisions of ''elementary'' particles such as protons and electrons. It is at these high energies that the predictions of quantum chromodynamics (QCD), the fundamental theory that describes the role of quarks and gluons in nuclear matter, come into play, and new phenomena are sought that may illuminate our view of the basic structure of matter on the sub-atomic scale, with important implications for the origins of matter on the cosmic scale. The RHIC experiments have recorded data from collisions of gold nuclei at the highest energies ever achieved in man-made particle accelerators. These collisions, of which hundreds of millions have now been examined, result in final states of unprecedented complexity, with thousands of produced particles radiating from the nuclear collision. All four of the RHIC experiments have moved quickly to analyze these data, and have begun to understand the phenomena that unfold from the moment of collision as these particles are produced. In order to provide benchmarks of simpler interactions against which to compare the gold-gold collisions, the experiments have gathered comparable samples of data from collisions of a very light nucleus (deuterium) with gold nuclei, as well as proton-proton collisions, all with identical beam energies and experimental apparatus. The early measurements have revealed compelling evidence for the existence of a new form of nuclear matter at extremely high density and temperature--a medium in which the predictions of QCD can be tested, and new phenomena explored, under conditions where the relevant degrees of freedom, over nuclear volumes, are expected to be those of quarks and gluons, rather than of hadrons. This is the realm of the quark gluon plasma, the predicted state of matter whose existence and properties are now being explored by the RHIC experiments.
Quark-Gluon Plasma: Present and Future
Tapan K. Nayak
2008-04-08
We review a sample of the experimental results from AGS to SPS and RHIC and their interpretations towards understanding of the Quark-Gluon Plasma. We discuss extrapolations of these results to the upcoming LHC experiments. Finally, we present the plans to probe the QCD critical point with an energy scan at RHIC and FAIR facilities.
Quark-Gluon Plasma: a New State of Matter
Brookhaven Lab
2010-01-08
Physicist Peter Steinberg explains the nature of the quark gluon plasma (QGP), a new state of matter produced at Brookhaven Lab's Relativistic Heavy Ion Collider (RHIC).
Quark Propagation in the Quark-Gluon Plasma
Xiangdong Li; Hu Li; C. M. Shakin; Qing Sun
2004-03-05
It has recently been suggested that the quark-gluon plasma formed in heavy-ion collisions behaves as a nearly ideal fluid. That behavior may be understood if the quark and antiquark mean-free- paths are very small in the system, leading to a "sticky molasses" description of the plasma, as advocated by the Stony Brook group. This behavior may be traced to the fact that there are relatively low-energy $q\\bar{q}$ resonance states in the plasma leading to very large scattering lengths for the quarks. These resonances have been found in lattice simulation of QCD using the maximum entropy method (MEM). We have used a chiral quark model, which provides a simple representation of effects due to instanton dynamics, to study the resonances obtained using the MEM scheme. In the present work we use our model to study the optical potential of a quark in the quark-gluon plasma and calculate the quark mean-free-path. Our results represent a specific example of the dynamics of the plasma as described by the Stony Brook group.
Quarkonia and Quark Drip Lines in Quark-Gluon Plasma
Cheuk-Yin Wong
2007-06-19
We extract the $Q$-$\\bar Q$ potential by using the thermodynamic quantities obtained in lattice gauge calculations. The potential is tested and found to give dissociation temperatures that agree well with those from lattice gauge spectral function analysis. Using such a $Q$-$\\bar Q$ potential, we examine the quarkonium states in a quark-gluon plasma and determine the `quark drip lines' which separate the region of bound color-singlet $Q\\bar Q$ states from the unbound region. The characteristics of the quark drip lines severely limit the region of possible bound $Q\\bar Q$ states with light quarks to temperatures close to the phase transition temperature. Bound quarkonia with light quarks may exist very near the phase transition temperature if their effective quark mass is of the order of 300-400 MeV and higher.
Jet conversions in a quark-gluon plasma
Liu, W.; Ko, Che Ming; Zhang, B. W.
2007-01-01
Quark and gluon jets traversing through a quark-gluon plasma not only lose their energies but also can undergo flavor conversions. The conversion rates via the elastic q((q) over bar )g -> gq((q) over bar )and the inelastic q (q) over bar gg...
Dynamics of quark-gluon plasma from Field correlators
A. Di Giacomo; E. Meggiolaro; Yu. A. Simonov; A. I. Veselov
2005-12-22
It is argued that strong dynamics in the quark-gluon plasma and bound states of quarks and gluons is mostly due to nonperturbative effects described by field correlators. The emphasis in the paper is made on two explicit calculations of these effects from the first principles: one analytic using gluelump Green's functions and another using independent lattice data on correlators. The resulting hadron spectra are investigated in the range T_c MEM data. The possible role of these bound states in the thermodynamics of quark-gluon plasma is discussed.
Tomography of the Quark-Gluon-Plasma by Charm Quarks
Song, Taesoo; Cabrera, Daniel; Torres-Rincon, Juan M; Tolos, Laura; Cassing, Wolfgang; Bratkovskaya, Elena
2015-01-01
We study charm production in ultra-relativistic heavy-ion collisions by using the Parton-Hadron-String Dynamics (PHSD) transport approach. The initial charm quarks are produced by the Pythia event generator tuned to fit the transverse momentum spectrum and rapidity distribution of charm quarks from Fixed-Order Next-to-Leading Logarithm (FONLL) calculations. The produced charm quarks scatter in the quark-gluon plasma (QGP) with the off-shell partons whose masses and widths are given by the Dynamical Quasi-Particle Model (DQPM) which reproduces the lattice QCD equation-of-state in thermal equilibrium. The relevant cross section are calculated in a consistent way by employing the effective propagators and couplings from the DQPM. Close to the critical energy density of the phase transition, the charm quarks are hadronized into $D$ mesons through coalescence and/or fragmentation depending on transverse momentum. The hadronized $D$ mesons then interact with the various hadrons in the hadronic phase with cross sect...
Tomography of the Quark-Gluon-Plasma by Charm Quarks
Taesoo Song; Hamza Berrehrah; Daniel Cabrera; Juan M. Torres-Rincon; Laura Tolos; Wolfgang Cassing; Elena Bratkovskaya
2015-07-02
We study charm production in ultra-relativistic heavy-ion collisions by using the Parton-Hadron-String Dynamics (PHSD) transport approach. The initial charm quarks are produced by the Pythia event generator tuned to fit the transverse momentum spectrum and rapidity distribution of charm quarks from Fixed-Order Next-to-Leading Logarithm (FONLL) calculations. The produced charm quarks scatter in the quark-gluon plasma (QGP) with the off-shell partons whose masses and widths are given by the Dynamical Quasi-Particle Model (DQPM) which reproduces the lattice QCD equation-of-state in thermal equilibrium. The relevant cross section are calculated in a consistent way by employing the effective propagators and couplings from the DQPM. Close to the critical energy density of the phase transition, the charm quarks are hadronized into $D$ mesons through coalescence and/or fragmentation depending on transverse momentum. The hadronized $D$ mesons then interact with the various hadrons in the hadronic phase with cross sections calculated in an effective lagrangian approach with heavy-quark spin symmetry. Finally, the nuclear modification factor $\\rm R_{AA}$ and the elliptic flow $v_2$ of $D^0$ mesons from PHSD are compared with the experimental data from the STAR Collaboration for Au+Au collisions at $\\sqrt{s_{\\rm NN}}$ =200 GeV. We find that in the PHSD the energy loss of $D$ mesons at high $p_T$ can be dominantly attributed to partonic scattering while the actual shape of $\\rm R_{AA}$ versus $p_T$ reflects the heavy quark hadronization scenario, i.e. coalescence versus fragmentation. Also the hadronic rescattering is important for the $\\rm R_{AA}$ at low $p_T$ and enhances the $D$-meson elliptic flow $v_2$.
Baryon number fluctuation and the quark-gluon plasma
Lin, ZW; Ko, Che Ming.
2001-01-01
We show that omega (B) or omega ((B) over bar), the squared baryon or antibaryon number fluctuation per baryon or antibaryon, is a possible signature for the quark-gluon plasma that is expected to be created in relativistic heavy ion collisions...
Viscous quark-gluon plasma model through fluid QCD approach
Djun, T. P.; Soegijono, B.; Mart, T.; Handoko, L. T. E-mail: Laksana.tri.handoko@lipi.go.id
2014-09-25
A Lagrangian density for viscous quark-gluon plasma has been constructed within the fluid-like QCD framework. Gauge symmetry is preserved for all terms inside the Lagrangian, except for the viscous term. The transition mechanism from point particle field to fluid field, and vice versa, are discussed. The energy momentum tensor that is relevant to the gluonic plasma having the nature of fluid bulk of gluon sea is derived within the model. By imposing conservation law in the energy momentum tensor, shear viscosity appears as extractable from the equation.
Quarkonia and heavy-quark relaxation times in the quark-gluon plasma
Riek, F.; Rapp, Ralf.
2010-01-01
A thermodynamic T-matrix approach for elastic two-body interactions is employed to calculate spectral functions of open and hidden heavy-quark systems in the quark-gluon plasma. This enables the evaluation of quarkonium bound-state properties...
J/psi Production in Quark-Gluon Plasma
Li Yan; Pengfei Zhuang; Nu Xu
2006-11-05
We study J/psi production at RHIC and LHC energies with both initial production and regeneration. We solve the coupled set of transport equation for the J/psi distribution in phase space and the hydrodynamic equation for evolution of quark-gluon plasma. At RHIC, continuous regeneration is crucial for the J/psi momentum distribution while the elliptic flow is still dominated by initial production. At LHC energy, almost all the initially created J\\psis are dissociated in the medium and regeneration dominates the J/psi properties.
The Fluid Nature of Quark-Gluon Plasma
W. A. Zajc
2008-02-25
Collisions of heavy nuclei at very high energies offer the exciting possibility of experimentally exploring the phase transformation from hadronic to partonic degrees of freedom which is predicted to occur at several times normal nuclear density and/or for temperatures in excess of $\\sim 170$ MeV. Such a state, often referred to as a quark-gluon plasma, is thought to have been the dominant form of matter in the universe in the first few microseconds after the Big Bang. Data from the first five years of heavy ion collisions of Brookhaven National Laboratory's Relativistic Heavy Ion Collider (RHIC) clearly demonstrate that these very high temperatures and densities have been achieved. While there are strong suggestions of the role of quark degrees of freedom in determining the final-state distributions of the produced matter, there is also compelling evidence that the matter does {\\em not} behave as a quasi-ideal state of free quarks and gluons. Rather, its behavior is that of a dense fluid with very low kinematic viscosity exhibiting strong hydrodynamic flow and nearly complete absorption of high momentum probes. The current status of the RHIC experimental studies is presented, with a special emphasis on the fluid properties of the created matter, which may in fact be the most perfect fluid ever studied in the laboratory.
Chiral electric separation effect in the quark-gluon plasma
Yin Jiang; Xu-Guang Huang; Jinfeng Liao
2015-02-16
In this paper we introduce and compute a new transport coefficient for the quark-gluon plasma (QGP) at very high temperature. This new coefficient $\\sigma_{\\chi e}$, the CESE (Chiral Electric Separation Effect) conductivity, quantifies the amount of axial current $\\vec J_A$ that is generated in response to an externally applied electric field $e\\vec E$: $\\vec J_A = \\sigma_{\\chi e} (e\\vec E)$. Starting with rather general argument in the kinetic theory framework, we show how a characteristic structure $\\sigma_{\\chi e}\\propto \\mu \\mu_5$ emerges, which also indicates the CESE as an anomalous transport effect occurring only in a parity-odd environment with nonzero axial charge density $\\mu_5\
Chiral electric separation effect in the quark-gluon plasma
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Jiang, Yin; Liao, Jinfeng; Huang, Xu-Guang
2015-02-02
In this paper we introduce and compute a new transport coefficient for the quark-gluon plasma (QGP) at very high temperature. This new coefficient ??e, the CESE (Chiral Electric Separation Effect) conductivity, quantifies the amount of axial current JA that is generated in response to an externally applied electric field eE: JA=??e(eE). Starting with a rather general argument in the kinetic theory framework, we show how a characteristic structure ??e???5 emerges, which also indicates the CESE as an anomalous transport effect occurring only in a parity-odd environment with nonzero axial charge density ?5 ? 0. Using the Hard-Thermal-Loop framework, the CESEmore »conductivity for the QGP is found to be ??e = (#)TTrfQeQA/g?ln(1/g) ??5/T² to the leading-log accuracy with the numerical constant (#) depending on favor content, e.g., (#)=14.5163 for u, d light flavors.« less
Chiral electric separation effect in the quark-gluon plasma
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Jiang, Yin [Indiana Univ., Bloomington, IN (United States); Liao, Jinfeng [Indiana Univ., Bloomington, IN (United States); Brookhaven National Lab., Upton, NY (United States); Huang, Xu-Guang [Fudan Univ., Shanghai (China)
2015-02-01
In this paper we introduce and compute a new transport coefficient for the quark-gluon plasma (QGP) at very high temperature. This new coefficient ??e, the CESE (Chiral Electric Separation Effect) conductivity, quantifies the amount of axial current JA that is generated in response to an externally applied electric field eE: JA=??e(eE). Starting with a rather general argument in the kinetic theory framework, we show how a characteristic structure ??e???5 emerges, which also indicates the CESE as an anomalous transport effect occurring only in a parity-odd environment with nonzero axial charge density ?5 ? 0. Using the Hard-Thermal-Loop framework, the CESE conductivity for the QGP is found to be ??e = (#)TTrfQeQA/g?ln(1/g) ??5/T² to the leading-log accuracy with the numerical constant (#) depending on favor content, e.g., (#)=14.5163 for u, d light flavors.
Leonard S. Kisslinger; Debasish Das
2015-05-12
This is a review of the Quantum Chrodynamics Cosmological Phase Transition, the Quark-Gluon Plasma, and the detection of the Quark-Gluon Plasma via RHIC(Relativistic Heavy Ion Collisions) production of heavy quark states using the mixed hybrid theory for the $\\Psi(2S)$ and $\\Upsilon(3S)$ states.
Thermalization of heavy quarks in the quark-gluon plasma
van Hees, H.; Rapp, Ralf.
2005-01-01
the BNL Relativistic Heavy-Ion Collider (RHIC) indicate the possibility that the D-meson v2 could be similar in magnitude to the one of light hadrons [10,11]. Since the c quark is rather heavy, this would be quite remarkable and could provide important... temperature) has been suggested as a mechanism to enhance partonic cross sections [12?14] to facilitate rapid thermalization of the bulk matter at RHIC as required in hy- drodynamical models. The notion of charmonium resonances in the QGP [15,16] has been...
ABSORPTION OF HARD AND THERMAL PHOTONS IN A QUARK-GLUON PLASMA...
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
* 1 R. J. Fries, B. Muller, D. K. Srivastava, "High-energy photons from passage of jets through quark gluon plasma", Phys. Rev. Lett. 90, 132301 (2003). * 2 P.B. Arnold,...
Photon production from a non-equilibrium quark-gluon plasma
Bhattacharya, Lusaka; Strickland, Michael
2015-01-01
We calculate leading-order medium photon yields from a quark-gluon plasma using (3+1)D anisotropic hydrodynamics. Non-equilibrium modifications of the photon rate is taken into account using a self-consistent modification of the particle distribution functions and the corresponding anisotropic hard-loop fermionic self-energies. We present predictions for the high-energy photon spectrum and photon elliptic flow as a function of transverse momentum, shear viscosity, and initial momentum-space anisotropy. Our findings indicate that high-energy photon production is sensitive to the assumed level of initial momentum-space anisotropy of the quark-gluon plasma. As a result, it may be possible to experimentally constrain the early-time momentum-space anisotropy of the quark-gluon plasma generated in relativistic heavy-ion collisions using high energy photon yields.
Dilepton as a Possible Signature for the Baryon-Rich Quark-Gluon Plasma
Xia, L. H.; Ko, Che Ming; Li, C. T.
1990-01-01
VOLUME 41, NUMBER 2 FEBRUARY 1990 Dilepton as a possible signature for the baryon-rich quark-gluon plasma L. H. Xia, ' C. M. Ko, and C. T. Li Cyclotron Institute and Center for Theoretical Physics, Texas A&M University, College Station, Texas 77843... at invariant masses between 2m?and 1 GeV. The total dilepton yield in this invariant mass region increases with the incident energy of the collision, but a saturation is seen once a baryon-rich quark-gluon plasma is formed in the initial stage. I...
Dilepton emission at temperature dependent baryonic quark-gluon plasma
S. Somorendro Singh; Yogesh Kumar
2012-08-04
A fireball of QGP is evoluted at temperature dependent chemical potential by a statistical model in the pionic medium. We study the dilepton emission rate at temperature dependent chemical potential (TDCP) from such a fireball of QGP. In this model, we take the dynamical quark mass as a finite value dependence on temparature and parametrization factor of the QGP evolution. The temperature and factor in quark mass enhance in the growth of the droplets as well as in the dilepton emission rates. The emission rate from the plasma shows dilepton spectrum in the intermediate mass region (IMR) of (1.0-4.0) GeV and its rate is observed to be a strong increasing function of the temperature dependent chemical potential for quark and antiquark annihilation.
Equation of state of a quark-gluon plasma using the Cornell potential
Udayanandan, K. M.; Sethumadhavan, P.; Bannur, V. M. [Department of Physics, University of Calicut, Kerala 673 635 (India)
2007-10-15
The equation of state (EOS) of quark-gluon plasma (QGP) using the Cornell potential based on Mayer's cluster expansion is presented. The string constant and the strong coupling constant for QGP are calculated. The EOS developed could describe the lattice EOS for pure gauge, two-flavor and three-flavor QGP qualitatively.
Introduction to the Quark-Gluon Plasma session in RJC 2014
Antonin Maire
2015-06-09
This contribution is a brief introduction to the physics of Quark-Gluon Plasma (QGP); the intention is to set the stage for the corresponding session proceedings of the "Rencontre Jeunes Chercheurs 2014". The text consists in a description of the Bjorken scenario of a heavy-ion collision followed by the introduction of the notion of hard probe for QGP studies.
Moritz Greif; Ioannis Bouras; Zhe Xu; Carsten Greiner
2014-11-17
Electric conductivity is sensitive to effective cross sections among the particles of the partonic medium. We investigate the electric conductivity of a hot plasma of quarks and gluons, solving the relativistic Boltzmann equation. In order to extract this transport coefficient, we employ the Green-Kubo formalism and, independently, a method motivated by the classical definition of electric conductivity. To this end we evaluate the static electric diffusion current upon the influence of an electric field. Both methods give identical results. For the first time, we obtain numerically the Drude electric conductivity formula for an ultrarelativistic gas of quarks and gluons employing constant isotropic binary cross sections. Furthermore, we extract the electric conductivity for a system of massless quarks and gluons including screened binary and inelastic, radiative $2\\leftrightarrow 3$ perturbative QCD scattering. Comparing with recent lattice results, we find an agreement in the temperature dependence of the conductivity.
Thermalization of mini-jets in a quark-gluon plasma
Iancu, Edmond
2016-01-01
We present the complete physical picture for the evolution of a high-energy jet propagating through a weakly-coupled quark-gluon plasma (QGP) by analytical and numerical investigation of thermalization of the soft components of the jet. Our results support the following physical picture: the leading particle emits a significant number of mini-jets which promptly evolve via multiple branching and thus degrade into a myriad of soft gluons, with energies of the order of the medium temperature $T$. Via elastic collisions with the medium constituents, these soft gluons relax to local thermal equilibrium with the plasma over a time scale which is considerably shorter than the typical lifetime of the mini-jet. The thermalized gluons form a tail which lags behind the hard components of the jet. Together with the background QGP, they behave hydrodynamically.
Radiative parton energy loss in expanding quark-gluon plasma with magnetic monopoles
B. G. Zakharov
2014-12-19
We study radiative parton energy loss in an expanding quark-gluon plasma with magnetic monopoles. We find that for realistic number density of thermal monopoles obtained in lattice simulations parton rescatterings on monopoles can considerably enhance energy loss for plasma produced in $AA$ collisions at RHIC and LHC energies. However, contrary to previous expectations, monopoles do not lead to the surface dominance of energy loss.
Anti pp searches for quark-gluon plasma at TeV I
Turkot, F.
1986-06-01
Three experiments that have been approved to run at TeV I are discussed from the viewpoint of their capability to search for evidence of the QCD phase transition in proton-antiproton collisions at 1.6 TeV. One of these experiments, E-735, was proposed as a dedicated search for quark-gluon plasma effects with a detector designed to study large total E/sub T/, low P/sub T/ individual particles. The other two, E-741 (CDF) and E-740 (DO), embody general purpose four-pi detectors designed primarily to study the physics of W and Z bosons and other large P/sub T/ phenomena. The detectors and their quark-gluon plasma signals are compared. 8 refs., 6 figs., 4 tabs. (LEW)
Equation of state of strongly coupled quark--gluon plasma -- Path integral Monte Carlo results
V. S. Filinov; M. Bonitz; Y. B. Ivanov; V. V. Skokov; P. R. Levashov; V. E. Fortov
2009-05-04
A strongly coupled plasma of quark and gluon quasiparticles at temperatures from $ 1.1 T_c$ to $3 T_c$ is studied by path integral Monte Carlo simulations. This method extends previous classical nonrelativistic simulations based on a color Coulomb interaction to the quantum regime. We present the equation of state and find good agreement with lattice results. Further, pair distribution functions and color correlation functions are computed indicating strong correlations and liquid-like behavior.
Event-by-event hydrodynamics: A better tool to study the Quark-Gluon plasma
Grassi, Frederique
2013-03-25
Hydrodynamics has been established as a good tool to describe many data from relativistic heavyion collisions performed at RHIC and LHC. More recently, it has become clear that it is necessary to use event-by-event hydrodynamics (i.e. describe each collision individually using hydrodynamics), an approach first developed in Brazil. In this paper, I review which data require the use of event-by-event hydrodynamics and what more we may learn on the Quark-Gluon Plasma with this.
Transport properties of the quark-gluon plasma from lattice QCD
Harvey B. Meyer
2009-09-10
I review the progress made in extracting transport properties of the quark-gluon plasma from lattice QCD simulations. The information on shear and bulk viscosity, the "low-energy constants" of hydrodynamics, is encoded in the retarded correlators of Tmunu, the energy-momentum tensor. Euclidean correlators, computable on the lattice, are related to the retarded correlators by an integral transform. The most promising strategy to extract shear and bulk viscosity is to study the shear and sound channel correlators where the hydrodynamic modes dominate. I present preliminary results from a comprehensive study of the gluonic plasma between 0.95Tc and 4.0Tc.
Jet-Triggered Photons from Back-Scattering Kinematics for Quark Gluon Plasma Tomography
Somnath De; Rainer J. Fries; Dinesh K. Srivastava
2014-10-11
High energy photons created from back-scattering of jets in quark gluon plasma are a valuable probe of the temperature of the plasma, and of the energy loss mechanism of quarks in the plasma. An unambiguous identification of these photons through single inclusive photon measurements and photon azimuthal anisotropies has so far been elusive. We estimate the spectra of back-scattering photons in coincidence with trigger jets for typical kinematic situations at the Large Hadron Collider and the BNL Relativistic Heavy Ion Collider. We find that the separation of back-scattering photons from other photon sources using trigger jets depends crucially on our ability to reliably estimate the initial trigger jet energy. We estimate that jet reconstruction techniques in heavy ion experiments need to be able to get to jet $R_{AA}\\gtrsim 0.7$ in central collisions for viable back-scattering signals.
Radiative energy loss in an anisotropic quark-gluon plasma
Roy, Pradip; Dutt-Mazumder, Abhee K.
2011-04-15
We calculate radiative energy loss of heavy and light quarks in an anisotropic medium (static) in a first-order opacity expansion. Such an anisotropy can result from the initial rapid longitudinal expansion of the matter created in relativistic heavy-ion collisions. Significant dependency of the energy loss on the anisotropy parameter {xi} and the direction of propagation of the partons with respect to the anisotropy axis is found. It is shown that the introduction of early-time momentum-space anisotropy can enhance the fractional energy loss in the direction of the anisotropy, whereas it decreases when the parton propagates perpendicular to the direction of the anisotropy.
Jet energy loss in the quark-gluon plasma by stream instabilities
Mannarelli, Massimo; Manuel, Cristina; Gonzalez-Solis, Sergi [Instituto de Ciencias del Espacio (IEEC/CSIC), Campus Universitat Autonoma de Barcelona, Facultat de Ciencies, Torre C5 E-08193 Bellaterra, Barcelona (Spain); Strickland, Michael [Department of Physics, Gettysburg College, Gettysburg, Pennsylvania 17325 (United States)
2010-04-01
We study the evolution of the plasma instabilities induced by two jets of particles propagating in opposite directions and crossing a thermally equilibrated non-Abelian plasma. In order to simplify the analysis we assume that the two jets of partons can be described with uniform distribution functions in coordinate space and by Gaussian distribution functions in momentum space. We find that while crossing the quark-gluon plasma, the jets of particles excite unstable chromomagnetic and chromoelectric modes. These fields interact with the particles (or hard modes) of the plasma inducing the production of currents; thus, the energy lost by the jets is absorbed by both the gauge fields and the hard modes of the plasma. We compare the outcome of the numerical simulations with the analytical calculation performed assuming that the jets of particles can be described by a tsunamilike distribution function. We find qualitative and semiquantitative agreement between the results obtained with the two methods.
Jet energy loss in the quark-gluon plasma by stream instabilities
Massimo Mannarelli; Cristina Manuel; Sergi Gonzalez-Solis; Michael Strickland
2009-12-01
We study the evolution of the plasma instabilities induced by two jets of particles propagating in opposite directions and crossing a thermally equilibrated non-Abelian plasma. In order to simplify the analysis we assume that the two jets of partons can be described with uniform distribution functions in coordinate space and by Gaussian distribution functions in momentum space. We find that while crossing the quark-gluon plasma, the jets of particles excite unstable chromomagnetic and chromoelectric modes. These fields interact with the particles (or hard modes) of the plasma inducing the production of currents; thus, the energy lost by the jets is absorbed by both the gauge fields and the hard modes of the plasma. We compare the outcome of the numerical simulations with the analytical calculation performed assuming that the jets of particles can be described by a tsunami-like distribution function. We find qualitative and semi-quantitative agreement between the results obtained with the two methods.
Effects of the Running of the QCD Coupling on the Energy Loss in the Quark-Gluon Plasma
Jens Braun; Hans-Jürgen Pirner
2006-10-25
Finite temperature modifies the running of the QCD coupling alpha_s(k,T) with resolution k. After calculating the thermal quark and gluon masses selfconsistently, we determine the quark-quark and quark-gluon cross sections in the plasma based on the running coupling. We find that the running coupling enhances these cross sections by factors of two to four depending on the temperature. We also compute the energy loss dE/dx of a high-energy quark in the plasma as a function of temperature. Our study suggests that, beside t-channel processes, inverse Compton scattering is a relevant process for a quantitative understanding of the energy loss of an incident quark in a hot plasma.
Comparison of Models of Critical Opacity in the Quark-Gluon Plasma
Xiangdong Li; C. M. Shakin
2004-07-20
In this work we discuss two methods of calculation of quark propagation in the quark-gluon plasma. Both methods make use of the Nambu-Jona-Lasinio model. The essential difference of these calculations is the treatment of deconfinement. A model of confinement is not included in the work of Gastineau, Blanquier and Aichelin [hep-ph/0404207], however, the meson states they consider are still bound for temperatures greater than the deconfinement temperature T_c. On the other hand, our model deals with unconfined quarks and includes a description of the q(bar)q resonances found in lattice QCD studies that make use of the maximum entropy method (MEM). We compare the q{bar)q cross sections calculated in these models.
Electromagnetic field and the chiral magnetic effect in the quark-gluon plasma
Kirill Tuchin
2015-05-13
Time evolution of electromagnetic field created in heavy-ion collisions strongly depends on the electromagnetic response of the quark-gluon plasma, which can be described by the Ohmic and chiral conductivities. The later is intimately related to the Chiral Magnetic Effect. I argue that a solution to the classical Maxwell equations at finite chiral conductivity is unstable due to the soft modes $kmagnetic field of a point charge. I show that finite chiral conductivity causes oscillations of magnetic field at early times.
Speed of sound in quark gluon plasma with one loop correction in mean field potential
Singh, S Somorendro
2015-01-01
We study thermodynamic properties and speed of sound in a free en- ergy evolution of quark-gluon plasma (QGP) with one loop correction factor in the mean-field potential. The values of the thermodynamic prop- erties like pressure, entropy and specific heat are calculated for a range of temperatures. The results agree with the recent lattice results. The speed of sound is found to be C2 s = 0.3 independent of parameters used in the loop correction which matches almost with lattice calculations.
RHIC PHYSICS: THE QUARK GLUON PLASMA AND THE COLOR GLASS CONDENSATE: 4 LECTURES
MCLERRAN,L.
2003-01-01
The purpose of these lectures is to provide an introduction to the physics issues which are being studied in the RHIC heavy ion program. These center around the production of new states of matter. The Quark Gluon Plasma is thermal matter which once existed in the big bang which may be made at RHIC. The Color Glass Condensate is a universal form of matter which controls the high energy limit of strong interactions. Both such forms of matter might be produced and probed at RHIC.
Speed of sound in quark gluon plasma with one loop correction in mean field potential
S. Somorendro Singh; R. Ramanathan
2015-05-14
We study thermodynamic properties and speed of sound in a free en- ergy evolution of quark-gluon plasma (QGP) with one loop correction factor in the mean-field potential. The values of the thermodynamic prop- erties like pressure, entropy and specific heat are calculated for a range of temperatures. The results agree with the recent lattice results. The speed of sound is found to be C2 s = 0.3 independent of parameters used in the loop correction which matches almost with lattice calculations.
Transport Properties of the Quark-Gluon Plasma -- A Lattice QCD Perspective
Harvey B. Meyer
2011-06-09
Transport properties of a thermal medium determine how its conserved charge densities (for instance the electric charge, energy or momentum) evolve as a function of time and eventually relax back to their equilibrium values. Here the transport properties of the quark-gluon plasma are reviewed from a theoretical perspective. The latter play a key role in the description of heavy-ion collisions, and are an important ingredient in constraining particle production processes in the early universe. We place particular emphasis on lattice QCD calculations of conserved current correlators. These Euclidean correlators are related by an integral transform to spectral functions, whose small-frequency form determines the transport properties via Kubo formulae. The universal hydrodynamic predictions for the small-frequency pole structure of spectral functions are summarized. The viability of a quasiparticle description implies the presence of additional characteristic features in the spectral functions. These features are in stark contrast with the functional form that is found in strongly coupled plasmas via the gauge/gravity duality. A central goal is therefore to determine which of these dynamical regimes the quark-gluon plasma is qualitatively closer to as a function of temperature. We review the analysis of lattice correlators in relation to transport properties, and tentatively estimate what computational effort is required to make decisive progress in this field.
Cavitation in a quark gluon plasma with finite chemical potential and several transport coefficients
S. M. Sanches Jr.; D. A. Fogaça; F. S. Navarra; H. Marrochio
2015-08-14
We study the effects of a finite chemical potential on the occurrence of cavitation in a quark gluon plasma (QGP). We solve the evolution equations of second order viscous relativistic hydrodynamics using three different equations of state. The first one was derived in lattice QCD and represents QGP at zero chemical potential. It was previously used in the study of cavitation. The second equation of state also comes from lattice QCD and is a recent parametrization of the QGP at finite chemical potential. The third one is similar to the MIT equation of state with chemical potential and includes nonperturbative effects through the gluon condensates. We conclude that at finite chemical potential cavitation in the QGP occurs earlier than at zero chemical potential. We also consider transport coefficients from a holographic model of a non-conformal QGP at zero chemical potential. In this case cavitation does not occur.
Cavitation in a quark gluon plasma with finite chemical potential and several transport coefficients
Sanches, S M; Navarra, F S; Marrochio, H
2015-01-01
We study the effects of a finite chemical potential on the occurrence of cavitation in a quark gluon plasma (QGP). We solve the evolution equations of second order viscous relativistic hydrodynamics using three different equations of state. The first one was derived in lattice QCD and represents QGP at zero chemical potential. It was previously used in the study of cavitation. The second equation of state also comes from lattice QCD and is a recent parametrization of the QGP at finite chemical potential. The third one is similar to the MIT equation of state with chemical potential and includes nonperturbative effects through the gluon condensates. We conclude that at finite chemical potential cavitation in the QGP occurs earlier than at zero chemical potential. We also consider transport coefficients from a holographic model of a non-conformal QGP at zero chemical potential. In this case cavitation does not occur.
Generalized Emission Functions for Photon Emission from Quark-Gluon Plasma
S. V. Suryanarayana
2006-06-06
The Landau-Pomeranchuk-Migdal effects on photon emission from the quark gluon plasma have been studied as a function of photon mass, at a fixed temperature of the plasma. The integral equations for the transverse vector function (${\\bf \\tilde{f}(\\tilde{p}_\\perp)}$) and the longitudinal function ($\\tilde{g}({\\bf \\tilde{p}_\\perp})$) consisting of multiple scattering effects are solved by the self consistent iterations method and also by the variational method for the variable set \\{$p_0,q_0,Q^2$\\}, considering the bremsstrahlung and the $\\bf aws$ processes. We define four new dynamical scaling variables, $x^b_T$,$x^a_T$,$x^b_L$,$x^a_L$ for bremsstrahlung and {\\bf aws} processes and analyse the transverse and longitudinal components as a function of \\{$p_0,q_0,Q^2$\\}. We generalize the concept of photon emission function and we define four new emission functions for massive photon emission represented by $g^b_T$, $g^a_T$, $g^b_L$, $g^a_L$. These have been constructed using the exact numerical solutions of the integral equations. These four emission functions have been parameterized by suitable simple empirical fits. In terms of these empirical emission functions, the virtual photon emission from quark gluon plasma reduces to one dimensional integrals that involve folding over the empirical $g^{b,a}_{T,L}$ functions with appropriate quark distribution functions and the kinematic factors. Using this empirical emission functions, we calculated the imaginary part of the photon polarization tensor as a function of photon mass and energy.
Energy loss, equilibration, and thermodynamics of a baryon rich strongly coupled quark-gluon plasma
Rougemont, Romulo; Finazzo, Stefano; Noronha, Jorge
2015-01-01
Lattice data for the QCD equation of state and the baryon susceptibility near the crossover phase transition (at zero baryon density) are used to determine the input parameters of a 5-dimensional Einstein-Maxwell-Dilaton holographic model that provides a consistent holographic framework to study both equilibrium and out-of-equilibrium properties of a hot and {\\it baryon rich} strongly coupled quark-gluon plasma (QGP). We compare our holographic equation of state computed at nonzero baryon chemical potential, $\\mu_B$, with recent lattice calculations and find quantitative agreement for the pressure and the speed of sound for $\\mu_B \\leq 400$ MeV. This holographic model is used to obtain holographic predictions for the temperature and $\\mu_B$ dependence of the drag force and the Langevin diffusion coefficients associated with heavy quark jet propagation as well as the jet quenching parameter $\\hat{q}$ and the shooting string energy loss of light quarks in the dense plasma. We find that the energy loss of heavy ...
Shear viscosity $?$ to electric conductivity $?_{el}$ ratio for the Quark-Gluon Plasma
A. Puglisi; S. Plumari; V. Greco
2015-05-04
The transport coefficients of strongly interacting matter are currently subject of intense theoretical and phenomenological studies due to their relevance for the characterization of the quark-gluon plasma produced in ultra relativistic heavy-ion collisions (uRHIC). We discuss the connection between the shear viscosity to entropy density ratio, $\\eta/s$, and the electric conductivity, $\\sigma_{el}$. Once the relaxation time is tuned to have a minimum value of $\\eta/s=1/4\\pi$ near the critical temperature $T_c$, one simultaneously predicts $\\sigma_{el}/T$ very close to recent lQCD data. More generally, we discuss why the ratio of $(\\eta/s)/(\\sigma_{el}/T)$ supplies a measure of the quark to gluon scattering rates whose knowledge would allow to significantly advance in the understanding of the QGP phase. We also predict that $(\\eta/s)/(\\sigma_{el}/T)$, independently on the running coupling $\\alpha_s(T)$, should increase up to about $\\sim 20$ for $T \\rightarrow T_c$, while it goes down to a nearly flat behavior around $\\simeq 4$ for $T \\geq 4\\, T_c$. Therefore we in general predict a stronger T dependence of $\\sigma_{el}/T$ with respect to $\\eta/s$ that in a quasiparticle approach is constrained by lQCD thermodynamics. A conformal theory, instead, predicts a similar T dependence of $\\eta/s$ and $\\sigma_{el}/T$.
Bag model of hadrons, dual QCD thermodynamics and Quark-Gluon Plasma
H. C. Chandola; Garima Punetha; H. Dehnen
2015-05-16
Using the grand canonical ensemble formulation of a multi-particle statistical system, the thermodynamical description of the dual QCD has been presented in terms of the bag model of hadrons and analyzed for the quark-gluon plasma phase of hadronic matter. The dual QCD bag construction has been shown to lead to the radial pressure on the bag surface in terms of the vector glueball masses of the magnetically condensed QCD vacuum. Constructing the grand canonical partition function to deal with the quark-gluon plasma phase of the non-strange hadrons, the energy density and the plasma pressure have been derived and used to understand the dynamics of the associated phase transition. The critical temperature for QGP-hadron phase transition has been derived and numerically estimated by using various thermodynamic considerations. A comparison of the values of the critical temperatures for QGP-hadron phase transition with those obtained for the deconfinement-phase transition, has been shown to lead to the relaxation of the system via a mixed phase of QGP and hot hadron gas. The associated profiles of the normalized energy density and the specific heat have been shown to lead to a huge latent heat generation and indicate the onset of a first-order QGP phase transition. The squared speed of sound has been shown to act as a physical measure of large thermodynamical fluctuations near transition point where it shows a large reduction in its value as compared to the conformal limit and has intimate connection with the evolution of fire-ball and QGP in heavy-ion collision events. The possible implications of the trace anomaly and conformal measure on QGP formation have been discussed and a considerable increase in the degrees of freedom and the associated interaction effects has been indicated around the transition region and discussed for its relevance with the modern heavy-ion collision experiments.
Quark-gluon plasma in the early Universe and in ultra-relativistic heavy-ion collisions
Greco, V.
2014-05-09
We briefly give an elementary introduction to the expansion of the Early Universe till when the phase transition of the quark-gluon plasma to a hadronic matter takes place. Then we describe some main element of the study of QGP by mean of ultra-relativistic heavy-ion collisions (uRHIC's)
Electrical conductivity of the quark-gluon plasma and soft photon spectrum in heavy-ion collisions
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Yin, Yi
2014-10-06
We extract the electrical conductivity ?0 of the quark gluon plasma (QGP) and study the effects of magnetic field and chiral anomaly on soft photon azimuthal anisotropy, v?, based on the thermal photon spectrum at 0.4GeV more »I found that the electrical conductivity at QGP temperature is in the range: 0.4 « less
Chiral vortical wave and induced flavor charge transport in a rotating quark-gluon plasma
Jiang, Yin; Liao, Jinfeng
2015-01-01
We show the existence of a new gapless collective excitation in a rotating fluid system with chiral fermions, named as the Chiral Vortical Wave (CVW). The CVW has its microscopic origin at the quantum anomaly and macroscopically arises from interplay between vector and axial charge fluctuations induced by vortical effects. The wave equation is obtained both from hydrodynamic current equations and from chiral kinetic theory and its solutions show nontrivial CVW-induced charge transport from different initial conditions. Using the rotating quark-gluon plasma in heavy ion collisions as a concrete example, we show the formation of induced flavor quadrupole in QGP and estimate the elliptic flow splitting effect for Lambda baryons that may be experimentally measured.
A T-Matrix Approach to Heavy Quark Interaction with Thermal Gluons in a Quark Gluon Plasma
Huggins, Kyle
2012-10-19
viii LIST OF FIGURES FIGURE Page 2.1 In-medium HQ free and internal energies determined using lattice data [12] in the triplet (solid lines), sextet (dotted lines), and 15-plet (dashed lines) channels at temperatures T = 1:2Tc (left) and 2Tc (right...) for charm-gluon at 1:2Tc (thick) and 2:0Tc (thin). Diagrams illustrate the s-wave (left) and p-wave (right) for charm-gluon in potential U for the triplet (top), sextet (2nd row), and 15-plet (3rd row) color channels. The bottom diagram corresponds...
Polymer Chains and Baryons in a Strongly Coupled Quark-Gluon Plasma
Jinfeng Liao; Edward V. Shuryak
2005-11-03
Recently there was a significant change of views on physical properties and underlying dynamics of Quark-Gluon Plasma at $T=170-350 MeV$, produced in heavy ion collisions at RHIC. Instead of being a gas of $q,g$ quasiparticles, a near-perfect liquid is observed. Also, precisely in this temperature interval, the interaction deduced from lattice studies is strong enough to support multiple binary bound states. This work is the first variational study of {\\em multibody} bound states. We will consider: (i) ``polymer chains'' of the type $\\bar q g g ..g q$; (ii) baryons $(qqq)$; (iii) closed (3-)chains of gluons $(ggg)$. We found that chains (i) form in exactly the same $T$ range as binary states, with the same binding {\\em per bond}. The binding and $T$-range for diquarks, baryons and closed 3-chains are also established. We point out that the presence of chains, or possibly even a chain network, may drastically change the transport properties of matter, such as charm diffusion or jet energy loss. We further suggest that it seems to exist only for $T=(1-1.5)T_c$ and thus there may be a ``latent period'' for charm/jet quenching in RHIC collisions, while matter cools down to such $T$.
Scott Pratt
2012-01-13
In the canonical picture of the evolution of the quark-gluon plasma during a high-energy heavy-ion collision, quarks are produced in two waves. The first is during the first fm/c of the collision, when gluons thermalize into the QGP. After a roughly isentropic expansion that roughly conserves the number of quarks, a second wave ensues at hadronization, 5-10 fm/c into the collision. Since each hadron contains at least two quarks, the majority of quark production occurs at this later time. For each quark produced in a heavy-ion collision, an anti-quark of the same flavor is created at the same point in space-time. Charge balance functions identify, on a statistical basis, the location of balancing charges for a given hadron, and given the picture above one expects the distribution in relative rapidity of balancing charges to be characterized by two scales. After first demonstrating how charge balance functions can be created using any pair of hadronic states, it will be shown how one can identify and study both processes of quark production. By considering balance functions of several hadronic species, and by performing illustrative calculations, this class of measurement appears to hold the prospect of providing the field's most stringent insight into the chemical evolution of the QGP.
Hadronic modes and quark properties in the quark-gluon plasma
Mannarelli, M.; Rapp, Ralf.
2005-01-01
temperatures, T similar or equal to 1-2 T(c). The quark-antiquark T matrix, including both color-singlet and color-octet channels, and corresponding quark self-energies and spectral functions are calculated self-consistently. The repulsive octet potential...
Thermal charm production in a quark-gluon plasma in Pb-Pb collisions at root S(NN)=5.5 TeV
Zhang, Ben-Wei; Ko, Che Ming; Liu, Wei.
2008-01-01
Charm production from the quark-gluon plasma created in the midrapidity of central heavy ion collisions at the Large Hadron Collider (LHC) is studied in the next-to-leading order in QCD. Using a schematic longitudinally boost...
Gert Aarts; Chris Allton; Seyong Kim; Maria Paola Lombardo; Mehmet B. Oktay; Sinead M. Ryan; D. K. Sinclair; Jon-Ivar Skullerud
2011-11-21
We study bottomonium spectral functions in the quark-gluon plasma in the Upsilon and eta_b channels, using lattice QCD simulations with two flavours of light quark on highly anisotropic lattices. The bottom quark is treated with nonrelativistic QCD (NRQCD). In the temperature range we consider, 0.42 MEM), used to construct the spectral functions, are discussed in some detail.
Heavy Quarkonia and Quark Drip Lines in Quark-Gluon Plasma
Cheuk-Yin Wong
2006-06-12
Using the potential model and thermodynamical quantities obtained in lattice gauge calculations, we determine the spontaneous dissociation temperatures of color-singlet quarkonia and the `quark drip lines' which separate the region of bound $Q\\bar Q$ states from the unbound region. The dissociation temperatures of $J/\\psi$ and $\\chi_b$ in quenched QCD are found to be 1.62$T_c$ and $1.18T_c$ respectively, in good agreement with spectral function analyses. The dissociation temperature of $J/\\psi$ in full QCD with 2 flavors is found to be 1.42$T_c$. For possible bound quarkonium states with light quarks, the characteristics of the quark drip lines severely limit the stable region close to the phase transition temperature. Bound color-singlet quarkonia with light quarks may exist very near the phase transition temperature if their effective quark mass is of the order of 300-400 MeV and higher.
Resonance recombination model and quark distribution functions in the quark-gluon plasma
Ravagli, L.; van Hees, H.; Rapp, Ralf.
2009-01-01
is adjusted to hydrodynamic simulations of semicentral Au-Au collisions at RHIC. To facilitate the applicability of the Langevin process, we focus on strange and charm quarks. Their interactions in the QGP are modeled using leading-order perturbative QCD...
Rougemont, Romulo
2015-01-01
Five dimensional black hole solutions that describe the QCD crossover transition seen in (2+1)-flavor lattice QCD calculations at nonzero baryon densities are used to obtain predictions for the baryon susceptibility, baryon conductivity, baryon diffusion constant, and thermal conductivity of the strongly coupled quark-gluon plasma in the range of temperatures $T=130-300$ MeV and baryon chemical potentials $\\mu_B=0-400$ MeV. Diffusive transport is predicted to be already suppressed in this region of the QCD phase diagram in a way that is consistent with the existence of a critical end point at larger baryon densities.
He, Yayun; Wang, Xin-Nian; Zhu, Yan
2015-01-01
A Linear Boltzmann Transport model within the perturbative QCD is developed for the study of parton propagation inside the quark-gluon plasma. Both leading partons and thermal recoil partons are tracked so that one can also study jet-induced medium excitations. In this study, we implement the complete set of elastic parton scattering processes and investigate elastic parton energy loss, transverse momentum broadening and their nontrivial energy and length dependence. We further investigate medium modifications of the jet shape and fragmentation functions of reconstructed jets. Contributions from thermal recoil partons are found to have significant influences on jet shape, fragmentation functions and angular distribution of reconstructed jets.
Yayun He; Tan Luo; Xin-Nian Wang; Yan Zhu
2015-05-21
A Linear Boltzmann Transport model within perturbative QCD is developed for the study of parton propagation inside the quark-gluon plasma. Both leading partons and thermal recoil partons are tracked so that one can also study jet-induced medium excitations. In this study, we implement the complete set of elastic parton scattering processes and investigate elastic parton energy loss, transverse momentum broadening and their nontrivial energy and length dependence. We further investigate medium modifications of the jet shape and fragmentation functions of reconstructed jets. Contributions from thermal recoil partons are found to have significant influences on jet shape, fragmentation functions and angular distribution of reconstructed jets.
Quark–gluon plasma as the possible source of cosmological dark radiation
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Birrell, Jeremiah; Rafelski, Johann
2015-02-01
The effective number of neutrinos, NeffNeff, obtained from CMB fluctuations accounts for all effectively massless degrees of freedom present in the Universe, including but not limited to the three known neutrinos. Using a lattice-QCD derived QGP equation of state, we constrain the observed range of NeffNeff in terms of the freeze-out of unknown degrees of freedom near to quark–gluon hadronization. We explore limits on the coupling of these particles, applying methods of kinetic theory, and discuss the implications of a connection between NeffNeff and the QGP transformation for laboratory studies of QGP.
SYSTEMATIC STUDIES OF HEAVY ION COLLISIONS TO SEARCH FOR QUARK-GLUON PLASMA
Fuqiang Wang
2007-11-29
This is the final technical report for DOE Outstanding Junior Investigator (OJI) Award, 'Systematic Studies of Heavy Ion Collisions to Search for Quark-Gluon Plasma', grant DE-FG02-02ER41219, Principal Investigator (PI) Fuqiang Wang. The research under the grant was divided into two phases. The first concentrated on systematic studies of soft hadron production at low transverse momentum (p{sub T}), in particular the production of (anti-)baryon and strangeness in heavy ion collisions at RHIC energies. The second concentrated on measurements of di-hadron and multi-hadron jet-correlations and investigations of medium response to jets. The research was conducted at the Relativistic Heavy-Ion Collider (RHIC) at BNL with the Solenoidal Tracker At RHIC (STAR) experiment. The total grant is $214,000. The grant established a PC farm solely used for this research. The PC farm consists of 8 nodes with a total of 16 CPUs and 3 disk servers of total 2 TB shared storage. The current balance of the grant is $19,985. The positive balance is because an initial purchase of $22,600 for the PC farm came out of the PI's start-up fund due to the lateness of the award. The PC farm is an integral part of the Purdue Physics Department's computer cluster. The grant supported two Ph.D. graduate students. Levente Molnar was supported from July 2002 to December 2003, and worked on soft hadron production. His thesis title is Systematics of Identified Particle Production in pp, d-Au and Au-Au Collisions at RHIC Energies. He graduated in 2006 and now is a Postdoctoral fellow at INFN Sezione di Bari, Italy working on the ALICE experiment at the LHC. Jason Ulery was supported from January 2004 to July 2007. His thesis title is Two- and Three-Particle Jet-Like Correlations. He defended his thesis in October 2007 and is moving to Frankfurt University, Germany to work on the ALICE experiment at the LHC. The research by this grant resulted in 7 journal publications (2 PRL, 1 PLB, 1 PRC, 2 submitted and 1 in preparation), and 14 invited talks and 10 contributed talks at major conferences. These are listed at end of this report.
Quarks and gluons in hadrons and nuclei
Close, F.E. (Oak Ridge National Lab., TN (USA) Tennessee Univ., Knoxville, TN (USA))
1989-12-01
These lectures discuss the particle-nuclear interface -- a general introduction to the ideas and application of colored quarks in nuclear physics, color, the Pauli principle, and spin flavor correlations -- this lecture shows how the magnetic moments of hadrons relate to the underlying color degree of freedom, and the proton's spin -- a quark model perspective. This lecture reviews recent excitement which has led some to claim that in deep inelastic polarized lepton scattering very little of the spin of a polarized proton is due to its quarks. This lecture discusses the distribution functions of quarks and gluons in nucleons and nuclei, and how knowledge of these is necessary before some quark-gluon plasma searches can be analyzed. 56 refs., 2 figs.
Electrical conductivity of the quark-gluon plasma and soft photon spectrum in heavy-ion collisions
Yin, Yi
2014-10-01
I extract the electrical conductivity ?0 of the quark gluon plasma (QGP) and study the effects of magnetic field and chiral anomaly on soft photon azimuthal anisotropy, v?, based on the thermal photon spectrum at 0.4GeV
plasma in hydrodynamic regime in the presence of magnetic field and chiral anomaly. By evolving the resulting soft thermal photon production rate over the realistic hydrodynamic background and comparing the results with the data from the PHENIX Collaboration, I found that the electrical conductivity at QGP temperature is in the range: 0.4
Yannis Burnier; Dmitri E. Kharzeev; Jinfeng Liao; Ho-Ung Yee
2011-03-07
Chiral Magnetic Wave (CMW) is a gapless collective excitation of quark-gluon plasma in the presence of external magnetic field that stems from the interplay of Chiral Magnetic (CME) and Chiral Separation Effects (CSE); it is composed by the waves of the electric and chiral charge densities coupled by the axial anomaly. We consider CMW at finite baryon density and find that it induces the electric quadrupole moment of the quark-gluon plasma produced in heavy ion collisions: the "poles" of the produced fireball (pointing outside of the reaction plane) acquire additional positive electric charge, and the "equator" acquires additional negative charge. We point out that this electric quadrupole deformation lifts the degeneracy between the elliptic flows of positive and negative pions leading to $v_2(\\pi^+) < v_2(\\pi^-)$, and estimate the magnitude of the effect.
Quark antiquark energies and the screening mass in a Quark-Gluon plasma at low and high temperatures
O. Kaczmarek; F. Zantow
2005-12-22
We discuss quark antiquark energies and the screening mass in hot QCD using the non-perturbative lattice approach. For this purpose we analyze properties of quark antiquark energies and entropies at infinitely large separation of the quark antiquark pair at low and high temperatures. In the limit of high temperatures these energies and entropies can be related perturbatively to the temperature dependence of the Debye mass and the coupling. On the one hand our analysis thus suggests that the quark antiquark energies at (infinite) large distances are rather related to the Debye screening mass and the coupling than to the temperature dependence of heavy-light meson masses. On the other hand we find no or only little differences in all mass scales introduced by us when changing from quenched to 2-flavor QCD at temperatures which are only moderately above the phase transition.
Gaining (mutual) information about quark/gluon discrimination
Thaler, Jesse
Discriminating quark jets from gluon jets is an important but challenging problem in jet substructure. In this paper, we use the concept of mutual information to illuminate the physics of quark/gluon tagging. Ideal quark/gluon ...
Roy A. Lacey; D. Reynolds; A. Taranenko; N. N. Ajitanand; J. M. Alexander; Fu-Hu Liu; Yi Gu; A. Mwai
2013-11-08
It is shown that the acoustic scaling patterns of anisotropic flow for different event shapes at a fixed collision centrality (shape-engineered events), provide robust constraints for the event-by-event fluctuations in the initial-state density distribution from ultrarelativistic heavy ion collisions. The empirical scaling parameters also provide a dual-path method for extracting the specific shear viscosity $(\\eta/s)_\\mathrm{QGP}$ of the quark-gluon plasma (QGP) produced in these collisions. A calibration of these scaling parameters via detailed viscous hydrodynamical model calculations, gives $(\\eta/s)_\\mathrm{QGP}$ estimates for the plasma produced in collisions of Au+Au ($\\sqrt{s_{NN}}= 0.2$ TeV) and Pb+Pb ($\\sqrt{s_{NN}}= 2.76$ TeV). The estimates are insensitive to the initial-state geometry models considered.
Monte Carlo Simulation for Elastic Energy Loss of High-Energy Partons in Quark-Gluon Plasma
Jussi Auvinen; Kari J. Eskola; Hannu Holopainen; Thorsten Renk
2011-06-13
We examine the significance of $2 \\rightarrow 2$ partonic collisions as the suppression mechanism of high-energy partons in the strongly interacting medium formed in ultrarelativistic heavy ion collisions. For this purpose, we have developed a Monte Carlo simulation describing the interactions of perturbatively produced, non-eikonally propagating high-energy partons with the quarks and gluons from the expanding QCD medium. The partonic collision rates are computed in leading-order perturbative QCD (pQCD), while three different hydrodynamical scenarios are used to model the medium. We compare our results with the suppression observed in $\\sqrt{s_{NN}}=200$ GeV Au+Au collisions at the BNL-RHIC. We find the incoherent nature of elastic energy loss incompatible with the measured data and the effect of the initial state fluctuations small.
Experimental treatment of Quark and Gluon Jets
Sona Pochybova
2011-07-01
The separate study of quark and gluon jets is vital for the interpretation of multiple variables behaviour observed in both high-energy hadron and heavy-ion collisions in the present and future experiments. We propose a set of jet-energy dependent cuts to be used to distinguish between quark and gluon jets experimentally based on a Monte-Carlo study of their properties. Further, we introduce the possibility to calibrate these cuts via gamma-jet and multi-jet events, which represent clean production channels for quark and gluon jets, respectively. The calibration can happen on real data and thus, reduces the dependence of the method performance on Monte-Carlo model predictions.
Jiechen Xu; Jinfeng Liao; Miklos Gyulassy
2015-08-03
A new model (CUJET3.0) of jet quenching in nuclear collisions coupled to bulk data constrained (VISH2+1D) viscous hydrodynamic backgrounds is constructed by generalizing the perturbative QCD based (CUJET2.0) model to include possible non-perturbative chromodynamical features of the QCD confinement transition near $T_c\\approx 160$ MeV. Two competing mechanisms are considered: (1) the suppression of quark and gluon chromo-electric-charged (cec) degrees of freedom (aka the semi-QGP model of Pisarski et al) and (2) the emergence of chromo-magnetic-monopole (cmm) degrees of freedom (aka the magnetic scenario of Shuryak-Liao). This semi Quark Gluon Monopole Plasma (sQGMP) model depends on two free parameters: (1) the saturating value of the QCD running coupling $\\alpha_c$ below $T_c$ and (2) the ratio $c_m$ of color electric to magnetic screening scales. The value of $\\alpha_c$ is fixed by fitting to a $single$ LHC reference datum, $R^{ch}_{PbPb}(p_T=12{\\rm GeV/c})\\approx 0.3$ for 20-30% centrality. Consistency is then tested by comparing predictions to $all$ $R^h_{AA}(p_T>10{\\rm GeV/c})$, $v^h_2(p_T>10{\\rm GeV/c})$, $h=\\pi,D,B$ data simultaneously at both RHIC and LHC. Robustness to uncertainties in modeling the suppression of cec degrees of freedom is tested by comparing results based on lattice data for Polyakov loop versus for quark susceptibility. The emergent cmm degrees of freedom are shown to solve robustly the long standing $R_{AA}$ vs $v_2$ puzzle by predicting a maximum of the jet quenching parameter field $\\hat{q}(E,T)/T^3$ near $T_c$. Robustness and consistency of jet quenching with observed bulk perfect fluidity is demonstrated by extrapolating the sQGMP $\\hat{q}$ down to thermal energy $E\\sim 3 T$ scales and showing that the $\\eta/s \\approx T^3/\\hat{q}$ falls close to the unitarity bound, $1/4\\pi$, in the range $(1-2)T_c$.
Vovchenko, V; Satarov, L M; Mishustin, I N; Csernai, L P; Kisel, I; Stoecker, H
2015-01-01
We study the possibility that partonic matter produced at early stage of ultrarelativistic heavy-ion collisions is out of chemical equilibrium. It is assumed that initially this matter is mostly composed of gluons, but quarks and antiquarks are produced at later times. The dynamical evolution of partonic system is described by the Bjorken-like ideal hydrodynamics with a time dependent quark fugacity. The results of this model are compared with those obtained by assuming the complete chemical equilibrium of partons already at the initial stage. It is shown that in a chemically non-equilibrium scenario the entropy gradually increases, and about 25% of the total final entropy is generated during the hydrodynamic evolution of deconfined matter. We argue that the (anti)quark suppression included in this approach may be responsible for reduced (anti)baryon to meson ratios observed in heavy-ion collisions at LHC energies.
Average gluon and quark jet multiplicities
A. V. Kotikov
2014-11-30
We show the results in [1,2] for computing the QCD contributions to the scale evolution of average gluon and quark jet multiplicities. The new results came due a recent progress in timelike small-x resummation obtained in the MSbar factorization scheme. They depend on two nonperturbative parameters with clear and simple physical interpretations. A global fit of these two quantities to all available experimental data sets demonstrates by its goodness how our results solve a longstandig problem of QCD. Including all the available theoretical input within our approach, alphas(Mz)=0.1199 +- 0.0026 has been obtained in the MSbar scheme in an approximation equivalent to next-to-next-to-leading order enhanced by the resummations of ln x terms through the NNLL level and of ln Q2 terms by the renormalization group. This result is in excellent agreement with the present world average.
Gaining (Mutual) Information about Quark/Gluon Discrimination
Andrew J. Larkoski; Jesse Thaler; Wouter J. Waalewijn
2014-12-03
Discriminating quark jets from gluon jets is an important but challenging problem in jet substructure. In this paper, we use the concept of mutual information to illuminate the physics of quark/gluon tagging. Ideal quark/gluon separation requires only one bit of truth information, so even if two discriminant variables are largely uncorrelated, they can still share the same "truth overlap". Mutual information can be used to diagnose such situations, and thus determine which discriminant variables are redundant and which can be combined to improve performance. Using both parton showers and analytic resummation, we study a two-parameter family of generalized angularities, which includes familiar infrared and collinear (IRC) safe observables like thrust and broadening, as well as IRC unsafe variants like $p_T^D$ and hadron multiplicity. At leading-logarithmic (LL) order, the bulk of these variables exhibit Casimir scaling, such that their truth overlap is a universal function of the color factor ratio $C_A/C_F$. Only at next-to-leading-logarithmic (NLL) order can one see a difference in quark/gluon performance. For the IRC safe angularities, we show that the quark/gluon performance can be improved by combining angularities with complementary angular exponents. Interestingly, LL order, NLL order, Pythia 8, and Herwig++ all exhibit similar correlations between observables, but there are significant differences in the predicted quark/gluon discrimination power. For the IRC unsafe angularities, we show that the mutual information can be calculated analytically with the help of a nonperturbative "weighted-energy function", providing evidence for the complementarity of safe and unsafe observables for quark/gluon discrimination.
A new method for determining the quark-gluon vertex
A. C. Aguilar; D. Binosi; D. Ibañez; J. Papavassiliou
2015-04-07
We present a novel nonperturbative approach for calculating the form factors of the quark-gluon vertex, in a general covariant gauge. The key ingredient of this method is the exact all-order relation connecting the conventional quark-gluon vertex with the corresponding vertex of the background field method, which is Abelian-like. When this latter relation is combined with the standard gauge technique, supplemented by a crucial set of transverse Ward identities, it allows the approximate determination of the nonperturbative behavior of all twelve form factors comprising the quark-gluon vertex, for arbitrary values of the momenta. The actual implementation of this procedure is carried out in the Landau gauge, in order to make contact with the results of lattice simulations performed in this particular gauge. The most demanding technical aspect involves the calculation of certain (fully-dressed) auxiliary three-point functions, using lattice data as input for the gluon propagators appearing in their diagrammatic expansion. The numerical evaluation of the relevant form factors in three special kinematical configurations (soft gluon and quark symmetric limit, zero quark momentum) is carried out in detail, finding rather good agreement with the available lattice data. Most notably, a concrete mechanism is proposed for explaining the puzzling divergence of one of these form factors observed in lattice simulations.
First Measurement of the Fraction of Top Quark Pair Production Through Gluon-Gluon Fusion
CDF Collaboration; T. Aaltonen
2008-04-08
We present the first measurement of the fraction of top quark pair production through gluon-gluon fusion. We use 0.96/fb of s**(1/2)=1.96 TeV p-pbar collision data recorded with the CDF II detector at Fermilab. We identify the candidate t-tbar events with a high-energy charged lepton, a neutrino candidate, and four or more jets. Using charged particles with low transverse momentum in t-tbar events, we find the fraction of top quark pair production through gluon-gluon fusion to be 0.07+/-0.14(stat)+/-0.07(syst), corresponding to a 95% confidence level upper limit of 0.33, in agreement with the standard model NLO prediction of 0.15+/-0.05.
Quarks and gluons in hadrons and nuclei
Close, F.E. (Oak Ridge National Lab., TN (USA) Tennessee Univ., Knoxville, TN (USA))
1989-01-01
These lectures discuss the particle-nuclear interface -- a general introduction to the ideas and application of colored quarks in nuclear physics, color, the Pauli principle, and spin flavor correlations -- this lecture shows how the magnetic moments of hadrons relate to the underlying color degree of freedom, and the proton's spin -- a quark model perspective. This lecture reviews recent excitement which has led some to claim that in deep inelastic polarized lepton scattering very little of the spin of a polarized proton is due to its quarks. 38 refs.
Inclusive Two-Gluon and Valence Quark-Gluon Production in DIS and pA
Jamal Jalilian-Marian; Yuri V. Kovchegov
2005-03-17
We calculate production cross sections of a forward quark-gluon pair and of two gluons at mid-rapidity in Deep Inelastic Scattering and in high energy proton-nucleus collisions. The calculation is performed in the framework of the Color Glass Condensate formalism. We first calculate the cross sections in the quasi-classical approximation, which includes multiple rescatterings in the target. We then proceed to include the effects of non-linear small-x evolution in the production cross sections. It is interesting to note that our result for the two-gluon production cross section appears to be in direct violation of AGK cutting rules, which is the first example of such violation in QCD. The calculated quark-gluon and gluon-gluon production cross sections can be used to construct theoretical predictions for two-particle azimuthal correlations at RHIC and LHC (I^{p(d)A}) as well as for Deep Inelastic Scattering experiments at HERA and eRHIC.
Controversy concerning the definition of quark and gluon angular momentum
Leader, Elliot [Blackett laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ (United Kingdom)
2011-05-01
A major controversy has arisen in QCD as to how to split the total angular momentum into separate quark and gluon contributions, and as to whether the gluon angular momentum can itself be split, in a gauge-invariant way, into a spin and orbital part. Several authors have proposed various answers to these questions and offered a variety of different expressions for the relevant operators. I argue that none of these is acceptable and suggest that the canonical expression for the momentum and angular momentum operators is the correct and physically meaningful one. It is then an inescapable fact that the gluon angular momentum operator cannot, in general, be split in a gauge-invariant way into a spin and orbital part. However, the projection of the gluon spin onto its direction of motion, i.e. its helicity is gauge invariant and is measured in deep inelastic scattering on nucleons. The Ji sum rule, relating the quark angular momentum to generalized parton distributions, though not based on the canonical operators, is shown to be correct, if interpreted with due care. I also draw attention to several interesting aspects of QED and QCD, which, to the best of my knowledge, are not commented upon in the standard textbooks on field theory.
Probing Quark-Gluon Interactions with Transverse Polarized Scattering
Slifer, K.; Rondon, O. A.; Crabb, D.; Day, D.; Frlez, E.; Lindgren, R.; McKee, P.; Norum, B.; Pocanic, D.; Prok, Y.; Sawatzky, B.; Smith, C.; Tajima, S.; Wang, K.; Zeier, M.; Zhu, H.; Aghalaryan, A.; Asaturyan, R.; Mkrtchyan, H.; Ahmidouch, A.
2010-09-03
We have extracted QCD matrix elements from our data on doubly polarized inelastic scattering of electrons on nuclei. We find the higher twist matrix element d{sub 2}-tilde, which arises strictly from quark-gluon interactions, to be unambiguously nonzero. The data also reveal an isospin dependence of higher twist effects if we assume that the Burkhardt-Cottingham sum rule is valid. The fundamental Bjorken sum rule obtained from the a{sub 0} matrix element is satisfied at our low momentum transfer.
Anisotropic hydrodynamics for mixture of quark and gluon fluids
Florkowski, Wojciech; Ryblewski, Radoslaw; Tinti, Leonardo
2015-01-01
A system of equations for anisotropic hydrodynamics is derived that describes a mixture of anisotropic quark and gluon fluids. The consistent treatment of the zeroth, first and second moments of the kinetic equations allows us to construct a new framework with more general forms of the anisotropic phase-space distribution functions than those used before. In this way, the main difficiencies of the previous formulations of anisotropic hydrodynamics for mixtures have been overcome and the good agreement with the exact kinetic-theory results is obtained.
Debye mass and heavy quark potential in a PNJL quark plasma
Jankowski, J. Blaschke, D.
2012-07-15
We calculate the Debye mass for the screening of the heavy quark potential in a plasma of massless quarks coupled to the temporal gluon background governed by the Polyakov loop potential within the PNJL model in RPA approximation. We give a physical motivation for a recent phenomenological fit of lattice data by applying the calculated Debye mass with its suppression in the confined phase due to the Polyakov loop to a description of the temperature dependence of the singlet free energy for QCD with a heavy quark pair at infinite separation. We compare the result to lattice data.
Color Glass Condensates in dense quark matter and quantum Hall states of gluons
Aiichi Iwazaki
2006-04-26
We apply the effective theory of color glass condensate to the analysis of gluon states in dense quark matter, in which the saturation region of gluons is also present. We find that in the region two point function of gluons shows algebraic long range order. The order is completely the same as the one gluons show in the dense quark matter, which form quantum Hall states. The order leads to the vanishing of massless gluon pole. We also find that the saturation region of gluons extends from small $x$ to even large $x\\lesssim 1$ in much dense quark matter. We point out a universality that the color glass condensate is a property of hadrons at high energy and of quark matter at high baryon density.
Quark deconfinement and gluon condensate in a weak magnetic field
Alejandro Ayala; C. A. Dominguez; L. A. Hernandez; M. Loewe; Juan Cristobal Rojas; Cristian Villavicencio
2015-07-01
We study QCD finite energy sum rules (FESR) for the axial-vector current correlator in the presence of a magnetic field, in the weak field limit and at zero temperature. We find that the perturbative QCD as well as the hadronic contribution to the sum rules get explicit magnetic field-dependent corrections and that these in turn induce a magnetic field dependence on the deconfinement phenomenological parameter s_0 and on the gluon condensate. The leading corrections turn out to be quadratic in the field strength. We find from the dimension d=2 first FESR that the magnetic field dependence of s_0 is proportional to the absolute value of the light-quark condensate. Hence, it increases with increasing field strength. This implies that the parameters describing chiral symmetry restoration and deconfinement behave similarly as functions of the magnetic filed. Thus, at zero temperature the magnetic field is a catalysing agent of both chiral symmetry breaking and confinement. From the dimension d=4 second FESR we obtain the behavior of the gluon condensate in the presence of the external magnetic field. This condensate also increases with increasing field strength.
Quark-gluon mixed condensate of the QCD vacuum in Holographic QCD
Hyun-Chul Kim; Youngman Kim
2008-08-27
We investigate the quark-gluon mixed condensate based on an AdS/QCD model. Introducing a holographic field dual to the operator for the quark-gluon mixed condensate, we obtain the corresponding classical equation of motion. Taking the mixed condensate as an additional free parameter, we show that the present scheme reproduces very well experimental data. A fixed value of the mixed condensate is in good agreement with that of the QCD sum rules.
A possible evidence of the hadron-quark-gluon mixed phase formation in nuclear collisions
V. A. Kizka; V. S. Trubnikov; K. A. Bugaev; D. R. Oliinychenko
2015-04-24
The performed systematic meta-analysis of the quality of data description (QDD) of existing event generators of nucleus-nucleus collisions allows us to extract a very important physical information. Our meta-analysis is dealing with the results of 10 event generators which describe data measured in the range of center of mass collision energies from 3.1 GeV to 17.3 GeV. It considers the mean deviation squared per number of experimental points obtained by these event generators, i.e. the QDD, as the results of independent meta-measurements. These generators and their QDDs are divided in two groups. The first group includes the generators which account for the quark-gluon plasma formation during nuclear collisions (QGP models), while the second group includes the generators which do not assume the QGP formation in such collisions (hadron gas models). Comparing the QDD of more than a hundred of different data sets of strange hadrons by two groups of models, we found two regions of the equal quality description of data which are located at the center of mass collision energies 4.4-4.87 GeV and 10.8-12 GeV. At the collision energies below 4.4 GeV the hadron gas models describe data much better than the QGP one and, hence, we associate this region with hadron phase. At the collision energies between 5 GeV and 10.8 GeV and above 12 GeV we found that QGP models describe data essentially better than the hadron gas ones and, hence, these regions we associate with the quark-gluon phase. As a result, the collision energy regions 4.4-4.87 GeV and 10.8-12 GeV we interpret as the energies of the hadron-quark-gluon mixed phase formation. Based on these findings we argue that the most probable energy range of the QCD phase diagram (tri)critical endpoint is 12-14 GeV.
\\THE POOL OF QUARKS AND GLUONS" The protons and neutrons, which make up nuclei, are not elementary in a simpli#12;ed way as a pool with three balls (quarks) of di#11;erent colours. Quarks cannot escape from the proton in the same way as balls are kept inside the pool by the boundaries. The quarks move freely except
Differential Higgs+jet production in bottom quark annihilation and gluon fusion
Marius Wiesemann
2012-11-05
We present recent developments concerning Higgs production in bottom quark annihilation and gluon fusion. For bottom quark annihilation, we show the transverse momentum distribution of the associated jets. Furthermore, we discuss the distribution of events into n-jet bins for n=0 and n>0 at NNLO and NLO, respectively. For gluon fusion, the quality of the heavy-top limit for differential quantities at O(\\alpha_s^4) is studied by taking into account higher order terms in the 1/m_{top} expansion.
Static potential for the quark-antiquark-gluon hybrid system in lattice QCD
Marco Cardoso; Pedro Bicudo; Orlando Oliveira
2007-10-09
The static gluon-quark-antiquark interaction is investigated using lattice QCD techniques. A Wilson loop adequate to the static hybrid three-body system is developed and, using a $24^3 \\times 48$ periodic lattice with $\\beta = 6.2$, the potential energy of the system is measured for different geometries. For the medium range behaviour, when the quarks are far apart, we find a string tension which is compatible with two fundamental strings. On the other hand, when the quark and antiquark are nearby, the string tension is larger than two fundamental strings and is compatible with the Casimir scaling.
Probing Quark-Gluon Structure of Matter with e-p and e-A Reactions
Jian-Ping Chen
2011-11-01
Understanding the strong interaction (QCD) in the truly strong ('non-perturbative') region remains a major challenge in modern physics. Nucleon and nuclei provide natural laboratories to study the strong interaction. The quark-gluon structure of the nucleon and nuclei are important by themselves since they are the main (>99%) part of the visible world. With electroweak interaction well-understood, e-p and e-A are clean means to probe the nucleon and nuclear structure and to study the strong interaction (QCD). Inclusive Deep-Inelastic Scattering (DIS) experiments have provided us with the most extensive information on the unpolarized and longitudinally-polarized parton (quark and gluon) distributions (PDFs). It has becoming clear that transverse spin and transverse structure (both transverse spatial structure via generalized parton distributions (GPDs) and transverse momentum structure via transverse- momentum-dependent distributions (TMDs)) study are crucial for a more complete understanding of the nucleon structure and the dynamics of the strong interaction(QCD). The transverse spin, GPDs and TMDs have been the subjects of increasingly intense theoretical and experimental study recently. With 12 GeV energy upgrade, Jefferson Lab (JLab) will provide the most precise multi-dimensional map of the TMDs and GPDs in the valence quark region through Semi-Inclusive DIS (SIDIS) and Deep-Exclusive experiments, providing a 3-d partonic picture of the nucleon in momentum and spatial spaces. The precision information on TMDs and GPDs will provide access to the quark orbital angular momentum and its correlation with the quark and the nucleon spins. The planned future Electron-Ion Collider (EIC) will enable a precision study of the TMDs and GPDs of the sea quarks and gluons, in addition to completing the study in the valence region. The EIC will also open a new window to study the role of gluons in nuclei.
Photon production from gluon mediated quark-anti-quark annihilation at confinement
Sarah Campbell
2015-06-20
Heavy ion collisions at RHIC produce direct photons at low transverse momentum, $p_{T}$ from 1-3 GeV/c, in excess of the $p$$+$$p$ spectra scaled by the nuclear overlap factor, $T_{AA}$. These low $p_{T}$ photons have a large azimuthal anisotropy, $v_{2}$. Theoretical models, including hydrodynamic models, struggle to quantitatively reproduce the large low $p_{T}$ direct photon excess and $v_{2}$ in a self-consistent manner. This paper presents a description of the low $p_{T}$ photon flow as the result of increased photon production from soft-gluon mediated $q$-$\\bar{q}$ interactions as the system becomes color-neutral. This production mechanism will generate photons that follow constituent quark number, $n_{q}$, scaling of $v_{2}$ with an $n_{q}$ value of two for direct photons. $\\chi^{2}$ comparisons of the published PHENIX direct photon and identified particle $v_{2}$ measurements finds that $n_{q}$-scaling applied to the direct photon $v_{2}$ data prefers the value $n_{q}=1.8$ and agrees with $n_{q}=2$ within errors in most cases. The 0-20% and 20-40% Au$+$Au direct photon data are compared to a coalescence-like Monte Carlo simulation that calculates the direct photon $v_{2}$ while describing the shape of the direct photon $p_{T}$ spectra in a consistent manner. The simulation, while systematically low compared to the data, is in agreement with the Au$+$Au measurement at $p_{T}photons will follow the modified $n_{q}$-scaling laws seen in identified hadron $v_{n}$ with an $n_{q}$ value of two.
Interpretation of Vector-like Quark Searches: Heavy Gluons in Composite Higgs Models
Juan Pedro Araque; Nuno Filipe Castro; Jose Santiago
2015-07-20
Pair production of new vector-like quarks in pp collisions is considered model independent as it is usually dominated by QCD production. We discuss the interpretation of vector-like quark searches in the case that QCD is not the only relevant production mechanism for the new quarks. In particular we consider the effect of a new massive color octet vector boson with sizeable decay branching ratio into the new quarks. We pay special attention to the sensitivity of the Large Hadron Collider experiments, both in run-1 and early run-2, to differences in the kinematical distributions from the different production mechanisms. We have found that even though there can be significant differences in some kinematical distributions at the parton level, the differences are washed out at the reconstruction level. Thus, the published experimental results can be reinterpreted in models with heavy gluons by simply rescaling the production cross section.
Gluon Radiation off Hard Quarks in a Nuclear Environment: Opacity Expansion
Urs Achim Wiedemann
2000-08-15
We study the relation between the Baier-Dokshitzer-Mueller-Peigne-Schiff (BDMPS) and Zakharov formalisms for medium-induced gluon radiation off hard quarks, and the radiation off very few scattering centers. Based on the non-abelian Furry approximation for the motion of hard partons in a spatially extended colour field, we derive a compact diagrammatic and explicitly colour trivial expression for the N-th order term of the kt-differential gluon radiation cross section in an expansion in the opacity of the medium. Resumming this quantity to all orders in opacity, we obtain Zakharov's path-integral expression (supplemented with a regularization prescription). This provides a new proof of the equivalence of the BDMPS and Zakharov formalisms which extends previous arguments to the kt-differential cross section. We give explicit analytical results up to third order in opacity for both the gluon radiation cross section of free incoming and of in-medium produced quarks. The N-th order term in the opacity expansion of the radiation cross section is found to be a convolution of the radiation associated to N-fold rescattering and a readjustment of the probabilities that rescattering occurs with less than N scattering centers. Both informations can be disentangled by factorizing out of the radiation cross section a term which depends only on the mean free path of the projectile. This allows to infer analytical expressions for the totally coherent and totally incoherent limits of the radiation cross section to arbitrary orders in opacity.
How do quarks and gluons lose energy in the QGP?
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Tannenbaum, M. J.
2015-03-10
RHIC introduced the method of hard scattering of partons as an in-situ probe of the the medium produced in A+A collisions. A suppression, RAA ? 0.2 relative to binary-scaling, was discovered for ?? production in the range 5 T NN = 200 GeV, and surprisingly also for single-electrons from the decay of heavy quarks. Both these results have been confirmed in Pb+Pb collisions at the LHC at ?sNN = 2.76 TeV. Interestingly, in this ?T range the LHC results for pions nearly overlap the RHIC results. Thus, due to the flattermore »spectrum, the energy loss in the medium at LHC in this ?T range must be ~ 40% larger than at RHIC. Unique at the LHC are the beautiful measurements of the fractional transverse momentum imbalance 1 – (?-carotT2/?-carotT1) of di-jets in Pb+Pb collisions. At the Utrecht meeting in 2011, I corrected for the fractional imbalance of di-jets with the same cuts in p-p collisions and showed that the relative fractional jet imbalance in Pb+Pb/p-p is ? 15% for jets with 120 T1 T jet ? 10 – 20 GeV/c, which appear to show a much larger fractional jet imbalance ? 45% in this lower ?-carotT range. The variation of apparent energy loss in the medium as a function of both ?T and ?sNN is striking and presents a challenge to both theory and experiment for improved understanding. There are many other such unresolved issues, for instance, the absence of evidence for a q-carot effect, due to momentum transferred to the medium by outgoing partons, which would widen the away-side di-jet and di-hadron correlations in a similar fashion as the kT-effect. Another issue well known from experiments at the CERN ISR, SpS and SpS collider is that parton-parton hard-collisions make negligible contribution to multiplicity or transverse energy production in p-p collisions–soft particles, with ?T AAch/d? = [(1 - x) (Npart)dNppch/d?2 + x (NcolldNppch/d?], seems to be an unphysical way to understand the deviation from Npart scaling. Based on recent p-p and d+A measurements, a more physical way is presented along with several other stimulating results and ideas from recent d+Au (p+Pb) measurements.« less
How do quarks and gluons lose energy in the QGP?
Tannenbaum, M. J.
2015-03-10
RHIC introduced the method of hard scattering of partons as an in-situ probe of the the medium produced in A+A collisions. A suppression, R_{AA} ? 0.2 relative to binary-scaling, was discovered for ?? production in the range 5 < ?_{T} < 20 GeV/c in central Au+Au collisions at ?s_{NN} = 200 GeV, and surprisingly also for single-electrons from the decay of heavy quarks. Both these results have been confirmed in Pb+Pb collisions at the LHC at ?s_{NN} = 2.76 TeV. Interestingly, in this ?_{T} range the LHC results for pions nearly overlap the RHIC results. Thus, due to the flatter spectrum, the energy loss in the medium at LHC in this ?_{T} range must be ~ 40% larger than at RHIC. Unique at the LHC are the beautiful measurements of the fractional transverse momentum imbalance 1 – (?-carot_{T2}/?-carot_{T1}) of di-jets in Pb+Pb collisions. At the Utrecht meeting in 2011, I corrected for the fractional imbalance of di-jets with the same cuts in p-p collisions and showed that the relative fractional jet imbalance in Pb+Pb/p-p is ? 15% for jets with 120 < ?-carot_{T1} < 360 GeV/c. CMS later confirmed this much smaller imbalance compared to the same quantity derived from two-particle correlations of di-jet fragments at RHIC corresponding to ?-carot_{T} jet ? 10 – 20 GeV/c, which appear to show a much larger fractional jet imbalance ? 45% in this lower ?-carot_{T} range. The variation of apparent energy loss in the medium as a function of both ?_{T} and ?s_{NN} is striking and presents a challenge to both theory and experiment for improved understanding. There are many other such unresolved issues, for instance, the absence of evidence for a q-carot effect, due to momentum transferred to the medium by outgoing partons, which would widen the away-side di-jet and di-hadron correlations in a similar fashion as the k_{T}-effect. Another issue well known from experiments at the CERN ISR, SpS and SpS collider is that parton-parton hard-collisions make negligible contribution to multiplicity or transverse energy production in p-p collisions–soft particles, with ?_{T} < 2 GeV/c, predominate. Thus an apparent hard scattering component for A+A multiplicity distributions based on a popular formula, dN^{AA}_{ch}/d? = [(1 - x) (N_{part})dN^{pp}_{ch}/d?2 + x (N_{coll}dN^{pp}_{ch}/d?], seems to be an unphysical way to understand the deviation from N_{part} scaling. Based on recent p-p and d+A measurements, a more physical way is presented along with several other stimulating results and ideas from recent d+Au (p+Pb) measurements.
Gluons and the Quark Sea at High Energies: Distributions, Polarization, Tomography
Boer, Daniel; Diehl, Markus; Milner, Richard; Venugopalan, Raju; Vogelsang, Werner; Kaplan, David; Montgomery, Hugh; Vigdor, Steven; Accardi, A.; Aschenauer, E.C.; Burkardt, M.; Ent, R.; Guzey, V.; Hasch, D.; Kumar, K.; Lamont, M.A.C.; Li, Ying-chuan; Marciano, W.; Marquet, C.; Sabatie, F.; Stratmann, M.; /more authors..
2012-06-07
This report on the science case for an Electron-Ion Collider (EIC) is the result of a ten-week program at the Institute for Nuclear Theory (INT) in Seattle (from September 13-November 19, 2010), motivated by the need to develop a strong case for the continued study of the QCD description of hadron structure in the coming decades. Hadron structure in the valence quark region will be studied extensively with the Jefferson Lab 12 GeV science program, the subject of an INT program the previous year. The focus of the INT program was on understanding the role of gluons and sea quarks, the important dynamical degrees of freedom describing hadron structure at high energies. Experimentally, the most direct and precise way to access the dynamical structure of hadrons and nuclei at high energies is with a high luminosity lepton probe in collider mode. An EIC with optimized detectors offers enormous potential as the next generation accelerator to address many of the most important, open questions about the fundamental structure of matter. The goal of the INT program, as captured in the writeups in this report, was to articulate these questions and to identify golden experiments that have the greatest potential to provide definitive answers to these questions. At resolution scales where quarks and gluons become manifest as degrees of freedom, the structure of the nucleon and of nuclei is intimately connected with unique features of QCD dynamics, such as confinement and the self-coupling of gluons. Information on hadron sub-structure in DIS is obtained in the form of 'snapshots' by the 'lepton microscope' of the dynamical many-body hadron system, over different momentum resolutions and energy scales. These femtoscopic snapshots, at the simplest level, provide distribution functions which are extracted over the largest accessible kinematic range to assemble fundamental dynamical insight into hadron and nuclear sub-structure. For the proton, the EIC would be the brightest femtoscope scale lepton-collider ever, exceeding the intensity of the HERA collider a thousand fold. HERA, with its center-of-mass (CM) energy of 320 GeV, was built to search for quark substructure. An EIC, with its scientific focus on studying QCD in the regime where the sea quarks and gluons dominate, would have a lower CM energy. In a staged EIC design, the CM energy will range from 50-70 GeV in stage I to approximately twice that for the full design. In addition to being the first lepton collider exploring the structure of polarized protons, an EIC will also be the first electron-nucleus collider, probing the gluon and sea quark structure of nuclei for the first time. Following the same structure as the scientific discussions at the INT, this report is organized around the following four major themes: (1) The spin and flavor structure of the proton; (2) Three dimensional structure of nucleons and nuclei in momentum and configuration space; (3) QCD matter in nuclei; and (4) Electroweak physics and the search for physics beyond the Standard Model. In this executive summary, we will briefly outline the outstanding physics questions in these areas and the suite of measurements that are available with an EIC to address these. The status of accelerator and detector designs is addressed at the end of the summary. Tables of golden measurements for each of the key science areas outlined are presented on page 12. In addition, each chapter in the report contains a comprehensive overview of the science topic addressed. Interested readers are encouraged to read these and the individual contributions for more details on the present status of EIC science.
Study of gluon versus quark fragmentation in ??gg? and e(+)e(-)?qq? events at s?=10 GeV
Baringer, Philip S.
1997-07-01
extract the mean multiplicities as a function of gg or q q¯ mass, for pure ggg and q q¯g samples. As shown in Fig. 4, the ratio of ^ Nchrg& resulting from gluon fragmentation to ^Nchrg& from quark fragmentation is Rchrg51.0460.02, after all the afore...& for gluons to ^Nchrg& for quarks mea- sured here is smaller than those found by the OPAL, ALEPH, SLD, and DELPHI experiments, at As;MZ0. The ratios compare as follows. Collaboration ^ N &g /^N&q Kinematic regime CLEO 96 1.0460.05 ^ E jet&,7 GeV DELPHI @4# 1...
Subjet multiplicity of gluon and quark jets reconstructed with the k? algorithm in pp-bar collisions
Baringer, Philip S.; Bean, Alice; Coppage, Don; Hebert, C.; Abazov, V. M.; Abbott, B.; Abdesselam, A.; Abolins, M.; Abramov, V.
2002-02-07
PHYSICAL REVIEW D, VOLUME 65, 052008Subjet multiplicity of gluon and quark jets reconstructed with the k? algorithm in pp¯ collisions V. M. Abazov,23 B. Abbott,57 A. Abdesselam,11 M. Abolins,50 V. Abramov,26 B. S. Acharya,17 D. L. Adams,59 M. Adams... of Virginia, Charlottesville, Virginia 22901 63University of Washington, Seattle, Washington 98195 ~Received 4 September 2001; published 7 February 2002!052008-2 th tr in th e at v t) or di C SUBJET MULTIPLICITY OF GLUON AND QUARK JETS . . . PHYSICAL REVIEW D...
Sungwoong Cho; Suyong Choi; Sehwook Lee; JaeHoon Lim; SungWoo Youn
2014-11-30
We report a measurement of the fraction of top quark pair events produced via gluon-gluon fusion in $p\\bar{p}$ collisions at $\\sqrt{s} = 1.96 ~\\rm TeV$ in lepton+jets final states using the full RunII data set corresponding to $9.7 ~\\rm fb^{-1}$ of integrated luminosity collected by the D\\O\\ experiment. We utilize a boosted decision tree to distinguish top quark pair events produced by $q\\bar{q}$ annihilation and $gg$ fusion. We perform a template fit to extract the $t\\bar{t}$ production fraction via $gg$ fusion and find $f_{gg} = 0.096 \\pm 0.039 ~(\\rm stat.) ~^{+0.077}_{-0.062} ~(\\rm syst.)$.
H. Malekzadeh
2008-10-29
Enforcing color and electric charge neutrality conditions on the three-flavor color superconducting matter, I derive the explicit form of the quark propagators and the gluon self-energies for the gapless and the ordinary color-flavor-locked phases.
Light-quark and gluon jet discrimination in pp collisions at ?s = 7 TeV with the ATLAS detector
Taylor, Frank E.
A likelihood-based discriminant for the identification of quark- and gluon-initiated jets is built and validated using 4.7 fb ?1 of proton–proton collision data at s?=7 TeV collected with the ATLAS detector at the LHC. ...
Direct and indirect constraints on CP-violating Higgs-quark and Higgs-gluon interactions
Y. -T. Chien; V. Cirigliano; W. Dekens; J. de Vries; E. Mereghetti
2015-10-02
We investigate direct and indirect constraints on the complete set of anomalous CP-violating Higgs couplings to quarks and gluons originating from dimension-6 operators, by studying their signatures at the LHC and in electric dipole moments (EDMs). We show that existing uncertainties in hadronic and nuclear matrix elements have a significant impact on the interpretation of EDM experiments, and we quantify the improvements needed to fully exploit the power of EDM searches. Currently, the best bounds on the anomalous CP-violating Higgs interactions come from a combination of EDM measurements and the data from LHC Run 1. We argue that Higgs production cross section measurements at the LHC Run 2 will not improve the constraints significantly. On the other hand, the bounds on the couplings scale roughly linearly with EDM limits, so that future theoretical and experimental EDM developments can have a major impact in pinning down interactions of the Higgs.
A Secular Quark Gluon Plasma Phase Preceding Black Hole Formation
Mitra, Abhas; Glendenning, Norman K.
2006-01-01
e ect of matter-radiation interaction and gravitationalenhanced matter- radiation interaction would accelerate theis trapped by matter-radiation interaction in the PNS. Since
Probing the Quark Sea and Gluons: the Electron-Ion Collider Projects
Rolf Ent
2012-04-01
EIC is the generic name for the nuclear science-driven Electron-Ion Collider presently considered in the US. Such an EIC would be the world’s first polarized electron-proton collider, and the world’s first e-A collider. Very little remains known about the dynamical basis of the structure of hadrons and nuclei in terms of the fundamental quarks and gluons of Quantum Chromodynamics (QCD). A large community effort to sharpen a compelling nuclear science case for an EIC occurred during a ten-week program taking place at the Institute for Nuclear Theory (INT) in Seattle from September 13 to November 19, 2010. The critical capabilities of a stage-I EIC are a range in center-of-mass energies from 20 to 70 GeV and variable, full polarization of electrons and light ions (the latter both longitudinal and transverse), ion species up to A=200 or so, multiple interaction regions, and a high luminosity of about 10{sup 34} electron-nucleons per cm{sup 2} and per second. The physics program of such a stage-I EIC encompass inclusive measurements (ep/A{yields}e'+X), which require detection of the scattered lepon and/or the full scattered hadronic debris with high precision, semi-inclusive processes (ep/A{yields}e'+h+X), which require detection in coincidence with the scattered lepton of at least one (current or target region) hadron; and exclusive processes (ep/A{yields}e'+N'/A'+{gamma}/m), which require detection of all particles in the reaction. The main science themes of an EIC are to i) map the spin and spatial structure of quarks and gluons in nucleons, ii) discover the collective effects of gluons in atomic nuclei, and (iii) understand the emergence of hadronic matter from color charge. In addition, there are opportunities at an EIC for fundamental symmetry and nucleon structure measurements using the electroweak probe. To truly make headway to image the sea quarks and gluons in nucleons and nuclei, the EIC needs high luminosity over a range of energies as more exclusive scattering probabilities are small, and any integrated detector/interaction region design needs to provide uniform coverage to detect spectator and diffractive products. This is because e-p and even more e-A colliders have a large fraction of their science related to what happens to the nucleon or ion beams. As a result, the philosophy of integration of complex detectors into an extended interaction region faces challenging constraints. Designs feature crossing angles between the protons or heavy ions during collisions with electrons, to remove potential problems for the detector induced by synchrotron radiation. Designs allocate quite some detector space before the final-focus ion quads, at the cost of luminosity, given that uniform detection coverage is a must for deep exclusive and diffractive processes. The integrated EIC detector/interaction region design at JLab focused on establishing full acceptance for such processes over a wide range of proton energies (20-100 GeV) with well achievable interaction region magnets. The detector design at BNL uses the higher ion beam energies to achieve good detection efficiency for instance for protons following a DVCS reaction, for proton beam energies starting from 100 GeV. Following a recommendation of the 2007 US Nuclear Science Long-Range Planning effort, the DOE Office of Nuclear Physics (DOE/NP) has allocated accelerator R&D funds to lay the foundation for a polarized EIC. BNL, in association with JLab and DOE/NP, has also established a generic detector R&D program to address the scientific requirements for measurements at a future EIC.
Mixed heavy-quark-gluon condensate in the stochastic vacuum model and dual superconductor
Dmitri Antonov
2005-09-30
The world-line formalism is used for the evaluation of the mixed heavy-quark-gluon condensate in two models of QCD - the stochastic vacuum model and the dual superconductor one. Calculations are performed for an arbitrary dimensionality of space-time $d\\ge 2$. While in the stochastic vacuum model, the condensate is UV finite up to $d=8$, in the dual superconductor model it is UV divergent at any $d\\ge 2$. A regularization of this divergence is proposed, which makes quantitative the condition of the type-II dual superconductor. The obtained results are generalized to the case of finite temperatures. Corrections to the both, mixed and standard, heavy-quark condensates, which appear due to the variation of the gauge field at the scale of the vacuum correlation length, are evaluated within the stochastic vacuum model. These corrections diminish the absolute values of the condensates, as well as the ratio of the mixed condensate to the standard one.
OZI violation in low energy omega and phi production in the pp system in a quark-gluon model
M. Dillig
2006-04-24
We investigate OZI violation in near-threshold omega and phi production in the pp system. Assuming ideal omega/phi mixing (corrections are estimated), the energy dependence of the ratio R(omega/phi) is analyzed in a perturbative quark-gluon exchange model up to the third other in the strong coupling constant alpha(s) with the proton represented as a quark - scalar diquark system. We give a very natural explanation of the violation of the OZI rule in omega/phi production and its energy dependence near the production thresholds.
Gluons and the quark sea at high energies: distributions, polarization, tomography
Boer, D.; Venugopalan, R.; Diehl, M.; Milner, R.; Vogelsang, W.; et al.
2011-09-30
This report is based on a ten-week program on Gluons and the quark sea at high-energies, which took place at the Institute for Nuclear Theory (INT) in Seattle in Fall 2010. The principal aim of the program was to develop and sharpen the science case for an Electron-Ion Collider (EIC), a facility that will be able to collide electrons and positrons with polarized protons and with light to heavy nuclei at high energies, offering unprecedented possibilities for in-depth studies of quantum chromodynamics (QCD). This report is organized around the following four major themes: (i) the spin and flavor structure of the proton, (ii) three dimensional structure of nucleons and nuclei in momentum and configuration space, (iii) QCD matter in nuclei, and (iv) Electroweak physics and the search for physics beyond the Standard Model. Beginning with an executive summary, the report contains tables of key measurements, chapter overviews for each of the major scientific themes, and detailed individual contributions on various aspects of the scientific opportunities presented by an EIC.
Lipatov, A. V.
2006-09-15
The inclusive production of heavy quarks and quarkonia in photon-photon collisions at the LEP2 collider is considered within the semihard (k{sub T}-factorization) QCD approach. The dependence of the total and differential cross sections for the production of heavy (c and b) quarks and D* and J/{psi} mesons on the choice of unintegrated gluon distribution is studied. The transition of a cc-bar charmed pair to observed J/{psi} mesons is described on the basis of the color-singlet model. The results of the calculations are compared with currently available experimental data obtained by the L3, OPAL, ALEPH, and DELPHI Collaborations. It is shown that the polarization properties of J/{psi} mesons at the LEP2 collider are sensitive to the behavior of unintegrated gluon distributions. This means that experimental investigations of the polarization properties of quarkonia in photon-photon collisions may provide a direct test of the dynamics of gluon distributions in the photon.
K. A. Bugaev; A. I. Ivanytskyi; D. R. Oliinychenko; E. G. Nikonov; V. V. Sagun; G. M. Zinovjev
2014-05-06
Here we develop the hadron resonance gas model with the Gaussian width of hadron resonances. This model allows us to treat the usual hadrons and the quark gluon bags on the same footing and to study the stability of the results obtained within different formulations of the hadron resonance gas model. In this work we perform a successful fit of 111 independent hadronic multiplicity ratios measured for $\\sqrt{s_{NN}} $= 2.7- 200 GeV. We demonstrate that in a narrow range of collision energy $\\sqrt{s_{NN}} =$ 4.3-4.9 GeV there exist peculiar irregularities in various thermodynamic quantities found at chemical freeze-out. The most remarkable irregularity is an unprecedented jump of the number of effective degrees of freedom observed in this narrow energy range which is seen in all realistic versions of the hadron resonance gas model. Therefore, the developed concept is called the non-smooth chemical freeze-out. We are arguing that these irregularities evidence for the possible formation of quark gluon bags. In order to develop other possible signals of their formation here we study the apparent width of wide hadronic resonances and quark gluon bags in a thermal environment. Two new effects generated for the wide resonances and quark gluon bags by a thermal medium are discussed here: the near threshold thermal resonance enhancement and the near threshold thermal resonance sharpening. On the basis of the new effects we argue that the most optimistic chance to find experimentally the quark gluon bags may be related to their sharpening and enhancement in a thermal medium. In this case the wide quark gluon bags may appear directly or in decays as narrow resonances that are absent in the tables of elementary particles and that have the apparent width about 50-120 MeV and the mass about or above 2.5 GeV.
ATLAS Collaboration
2014-09-19
A likelihood-based discriminant for the identification of quark- and gluon-initiated jets is built and validated using 4.7 fb$^{-1}$ of proton-proton collision data at $\\sqrt{s}$ = 7 TeV collected with the ATLAS detector at the LHC. Data samples with enriched quark or gluon content are used in the construction and validation of templates of jet properties that are the input to the likelihood-based discriminant. The discriminating power of the jet tagger is established in both data and Monte Carlo samples within a systematic uncertainty of 10-20%. In data, light-quark jets can be tagged with an efficiency of 50% while achieving a gluon-jet mis-tag rate of 25% in a $p_T$ range between 40 GeV and 360 GeV for jets in the acceptance of the tracker. The rejection of gluon-jets found in the data is significantly below what is attainable using a Pythia 6 Monte Carlo simulation, where gluon-jet mis-tag rates of 10% can be reached for a 50% selection efficiency of light-quark jets using the same jet properties.
Heavy quark production from jet conversions in a quark-gluon plasma
Liu, W.; Fries, Rainer J.
2008-01-01
Recently, it has been demonstrated that the chemical composition of jets in heavy ion collisions is significantly altered compared to the jets in the vacuum. This signal can be used to probe the medium formed in nuclear collisions. In this study we...
Total cross section of neutron-proton scattering at low energies in quark-gluon model
V. A. Abramovsky; N. V. Radchenko
2011-07-30
We show that analysis of nonrelativistic neutron-proton scattering in a framework of relativistic QCD based quark model can give important information about QCD vacuum structure. In this model we describe total cross section of neutron-proton scattering at kinetic energies of projectile neutron from 1 eV up to 1 MeV.
Higgs boson production with one bottom quark including higher-order soft-gluon corrections
B. Field; C. B. Jackson; L. Reina
2007-07-12
A Higgs boson produced in association with one or more bottom quarks is of great theoretical and experimental interest to the high-energy community. A precise prediction of its total and differential cross-section can have a great impact on the discovery of a Higgs boson with large bottom-quark Yukawa coupling, like the scalar (h^0 and H^0) and pseudoscalar (A^0) Higgs bosons of the Minimal Supersymmetric Standard Model (MSSM) in the region of large \\tan\\beta. In this paper we apply the threshold resummation formalism to determine both differential and total cross-sections for b g \\to b\\Phi (where \\Phi = h^0, H^0), including up to next-to-next-to-next-to-leading order (NNNLO) soft plus virtual QCD corrections at next-to-leading logarithmic (NLL) accuracy. We present results for both the Fermilab Tevatron and the CERN Large Hadron Collider (LHC).
M. Cardoso; N. Cardoso; P. Bicudo
2009-12-16
The chromoelectric and chromomagnetic fields, created by a static gluon-quark-antiquark system, are computed in quenched SU(3) lattice QCD, in a $24^3\\times 48$ lattice at $\\beta=6.2$ and $a=0.07261(85) fm$. We compute the hybrid Wilson Loop with two spatial geometries, one with a U shape and another with an L shape. The particular cases of the two gluon glueball and quark-antiquark are also studied, and the Casimir scaling is investigated in a microscopic perspective. This microscopic study of the colour fields is relevant to understand the structure of hadrons, in particular of the hybrid excitation of mesons. This also contributes to understand confinement with flux tubes and to discriminate between the models of fundamental versus adjoint confining strings, analogous to type-II and type-I superconductivity.
Geek-Up[12.03.2010]: Halomonadaceae Bacteria and the Return of Quark Gluon
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AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on Delicious Rank EERE:FinancingPetroleum12,Executive Compensation References: FARWashers |Gamma-RayPlasma | Department of
Proton structure and tensor gluons
George Savvidy
2014-07-31
We consider a possibility that inside the proton and, more generally, inside the hadrons there are additional partons - tensor-gluons, which can carry a part of the proton momentum. The tensor-gluons have zero electric charge, like gluons, but have a larger spin. Inside the proton a nonzero density of the tensor-gluons can be generated by the emission of tensor-gluons by gluons. The last mechanism is typical for non-Abelian tensor gauge theories, in which there exists a gluon-tensor-tensor vertex of order g. Therefore the number of gluons changes not only because a quark may radiate a gluon or because a gluon may split into a quark-antiquark pair or into two gluons, but also because a gluon can split into two tensor-gluons. The process of gluon splitting suggests that part of the proton momentum which was carried by neutral partons is shared between vector and tensor gluons. We derive evolution equations for the parton distribution functions which take into account these new processes. The momentum sum rule allows to find the tensor-gluons contribution to the Callan-Simanzik beta function and to calculate the corresponding anomalous dimensions. This contribution changes the behavior of the structure functions, and the logarithmic correction to the Bjorken scaling becomes more mild. This also influences the unification scale at which the coupling constants of the Standard Model merge, shifting its value to lower energies of order of 40 TeV.
Study on Screenning Length of Quark-AntiQuark Pair in a Hot Plasma of Two Dimensional Sphere
Atmaja, Ardian Nata
2011-01-01
We study screening length of a quark-antiquark pair moving in a plasma, corresponds to four dimensional AdS-Schwarzschild Black Hole, in AdS/CFT correspondence. The geodesic solution of the ends of string at the boundary reduces the problem to the motion in equatorial plane in which the separation length $L$ of quark-antiquark pair is parallel to the angular velocity $\\omega$. The string configuration for quark-antiquark pair is parameterized by momentum transfer $P$ which is related to momentum transfer in the drag force configuration. We compare the result by computing the screening length in quark-antiquark reference frame where the gravity dual is four dimensional Kerr-AdS Black Hole and we find a relation between mass parameters $M_{Sch}$ of Schwarzschild-AdS Black Hole and $M_{Kerr}$ of Kerr-AdS Black Hole in large mass limit.
Large mass dileptons from the passage of jets through a quark gluon plasma
Srivastava, DK; Gale, C.; Fries, Rainer J.
2003-01-01
-09-05 Proceedings of the 14th International Conference for Enhanced Building Operations, Beijing, China, September 14-17, 2014 Agenda ? Room Control fundamentals and evolution ? Challenges ? The Smart Room Control approach ? Benefits ? Market applications ? Typical... Configurations ? Summary ESL-IC-14-09-05 Proceedings of the 14th International Conference for Enhanced Building Operations, Beijing, China, September 14-17, 2014 Room Control – System Fundamentals ? HVAC ? Terminal units ? Temperature and air flow control...
Geek-Up[11.05.10]: Quark Gluon Plasma, Solar-Power Generating...
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auditorium at 2 a.m. EDT July 4 and waited for the latest announcement regarding the Higgs boson. When CERN Director-General Rolf-Dieter Heuer said the words - "I think we have it"...
Hard Probes of the Quark Gluon Plasma in Heavy Ion Collisions
Salgado, Carlos A
2011-01-01
The medium-modifications of processes characterized by the presence of a hard scale provide the most diverse tools to characterize the properties of the matter created in high-energy nuclear collisions. Indeed, jet quenching, the suppression of particles produced at high transverse momentum, has been established at RHIC almost a decade ago as one of the main tools in heavy-ion collisions. The melting of quarkonia is expected to provide also information about the temperature and the properties of the produced medium. The beginning of the LHC era for hot QCD studies starts with the first nuclear beams in 2010. The amount of information produced by this first run is overwhelming: The three experiments with nuclear program (ALICE, ATLAS and CMS) have provide new results in basically all subjects considered in previous experiments and have also shown the potential to make nuclear collisions at the TeV scale for the first time. I will review what the results from both RHIC and LHC imply for our understanding of hot...
High momentum dilepton production from jets in a quark gluon plasma
Turbide, Simon; Gale, Charles; Srivastava, Dinesh K.; Fries, Rainer J.
2006-01-01
with a Monte Carlo code, EGS4, to calculate absorbed fraction of energy and specific absorbed fraction of energy for photon and electron sources located in one of thirteen chosen source regions. These calculations were made for radiations in the energy...
J/psi Production in Quark-Gluon Plasma (Journal Article) | SciTech Connect
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J/psi Production in Quark-Gluon Plasma (Journal Article) | SciTech Connect
Office of Scientific and Technical Information (OSTI)
AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity of NaturalDukeWakefieldSulfate Reducing(Journalspectroscopy of aerosols in(JournalTechnical Report: IsLi2SO4(aq)It's aJournal
Relation between quark-antiquark potential and quark-antiquark free energy in hadronic matter
Zhen-Yu Shen; Xiao-Ming Xu
2015-07-07
In the high-temperature quark-gluon plasma and its subsequent hadronic matter created in a high-energy nucleus-nucleus collision, the quark-antiquark potential depends on the temperature. The temperature-dependent potential is expected to be derived from the free energy obtained in lattice gauge theory calculations. This requires one to study the relation between the quark-antiquark potential and the quark-antiquark free energy. When the system's temperature is above the critical temperature, the potential of a heavy quark and a heavy antiquark almost equals the free energy, but the potential of a light quark and a light antiquark, of a heavy quark and a light antiquark and of a light quark and a heavy antiquark is substantially larger than the free energy. When the system's temperature is below the critical temperature, the quark-antiquark free energy can be taken as the quark-antiquark potential. This allows one to apply the quark-antiquark free energy to study hadron properties and hadron-hadron reactions in hadronic matter.
Heavy Quark and Quarkonium Transport in High Energy Nuclear Collisions
Zhou, Kai; Xu, Nu; Zhuang, Pengfei
2016-01-01
The strong interaction between heavy quarks and the quark gluon plasma makes the open and hidden charm hadrons be sensitive probes of the deconfinement phase transition in high energy nuclear collisions. Both the cold and hot nuclear matter effects change with the colliding energy and significantly influence the heavy quark and charmonium yield and their transverse momentum distributions. The ratio of averaged quarkonium transverse momentum square and the elliptic flow reveal the nature of the QCD medium created in heavy ion collisions at SPS, RHIC and LHC energies.
Parton Energy Loss in Two-Stream Plasma System
M. E. Carrington; K. Deja; St. Mrowczynski
2012-01-06
The energy loss of a fast parton scattering elastically in a weakly coupled quark-gluon plasma is formulated as an initial value problem. The approach is designed to study an unstable plasma, but it also reproduces the well known result of energy loss in an equilibrium plasma. A two-stream system, which is unstable due to longitudinal chromoelectric modes, is discussed here some detail. In particular, a strong time and directional dependence of the energy loss is demonstrated.
Geek-Up[11.05.10]: Quark Gluon Plasma, Solar-Power Generating Windows and CCS Field Studies
Broader source: Energy.gov [DOE]
Large Hadron Collider's (LHC) first record-setting run of high-energy proton collisions, new transparent film capable of absorbing light and generating electrical charge developed, and field test finds that opportunities to permanently store carbon in unmineable seams of lignite may be more widespread than previously documented -- all in this week's Geek-Up.
Huey-Wen Lin; Keh-Fei Liu
2011-11-02
It is argued by the author that the canonical form of the quark energy-momentum tensor with a partial derivative instead of the covariant derivative is the correct definition for the quark momentum and angular momentum fraction of the nucleon in covariant quantization. Although it is not manifestly gauge invariant, its matrix elements in the nucleon will be non-vanishing and are gauge invariant. We test this idea in the path-integral quantization by calculating correlation functions on the lattice with a gauge-invariant nucleon interpolation field and replacing the gauge link in the quark lattice momentum operator with unity, which corresponds to the partial derivative in the continuum. We find that the ratios of three-point to two-point functions are zero within errors for both the u and d quarks, contrary to the case without setting the gauge links to unity.
Nuclear-matter--quark-matter phase diagram with strangeness
Barz, H. W.; Friman, B. L.; Knoll, J.; Schulz, H.
1989-07-01
A phenomenological equation of state of strongly interacting matter, including strange degrees of freedom, is presented. It is shown that the hyperon and kaon interactions must be included, in order to obtain a reasonable description of the deconfinement transition at high baryon densities. The consequences of kaon condensation on the nuclear-matter--quark-matter phase diagram are explored. The relative particle abundances obtained in an isentropic expansion of a blob of quark-gluon plasma are presented for different initial conditions. Implications for ultrarelativistic heavy-ion collisions are briefly discussed.
Higgs Boson Production via Gluon Fusion: Soft-Gluon Resummation including Mass Effects
Schmidt, Timo
2015-01-01
We analyze soft and collinear gluon resummation effects at the N$^3$LL level for Standard Model Higgs boson production via gluon fusion $gg\\to H$ and the neutral scalar and pseudoscalar Higgs bosons of the minimal supersymmetric extension at the N$^3$LL and NNLL level, respectively. We introduce refinements in the treatment of quark mass effects and subleading collinear gluon effects within the resummation. Soft and collinear gluon resummation effects amount to up to about 5% beyond the fixed-order results for scalar and pseudoscalar Higgs boson production.
van Hees, H.; Greco, V.; Rapp, Ralf.
2006-01-01
strongly interacting QGP (sQGP), as well as parton coalescence, can play an essential role in the interpretation of recent data from the BNL Relativistic Heavy-Ion Collider (RHIC), and thus illuminate the nature of the sQGP and its hadronization. Our main...
QCD thermodynamics with Wilson quarks at large kappa
Tom Blum; Thomas A. DeGrand; Carleton DeTar; Steven Gottlieb; A. Hasenfratz; Leo Karkkainen; D. Toussaint; R. L. Sugar
1994-04-12
We have extended our study of the high temperature transition with two flavors of Wilson quarks on 12^3 x 6 lattices to kappa=0.19. We have also performed spectrum calculations on 12^3 x 24 lattices at kappa=0.19 to find the physical lattice spacing and quark mass. At this value of kappa the transition is remarkable in that the plaquette and psi-bar-psi show a large discontinuity while the Polyakov loop changes very little. This and several other features of the transition are more suggestive of a bulk transition than a transition to a quark-gluon plasma. However, if the temperature is estimated using the rho mass as a standard, the result is about 150 MeV, in agreement with the value found for the thermal transition with Kogut-Susskind quarks. uuencoded compressed Postscript file
Peterson, Carsten
March 1990 LU TP 903 Finding Gluon Jets with a Neural Trigger Leif L¨onnblad 1 , Carsten Peterson classifier we are able to separate gluon from quark jets origi nating from Monte Carlo generated e + e how to separate gluon and quark jets using a neural network identifier. Being able to distinguish
Gluon sivers and experimental considerations for TMDs
Thomas Burton
2012-12-14
The study and characterisation of transverse-momentum-dependent distribution functions (TMDs) is a major goal of the Electron-Ion Collider (EIC) physics programme. The study of gluon TMDs poses a greater challenge than for quark TMDs in DIS measurements, as gluons do not directly couple to photons. The study of D meson pairs has been proposed to provide access to gluon TMDs, but is demanding due to the rarity of D production. Here, we discuss the feasibility of such a measurement, and touch upon wider issues to be considered when measuring TMDs at the EIC.
Gluons and the NJL coupling constant
Braghin, Fábio L.; Barros Jr, Ednaldo; Paulo Jr, Ademar
2014-11-11
The QCD origin of the NJL model is re-analysed by considering the gluon condensate of order two . The key point is the treatment of the gluon interactions. To linearize the action the auxiliary variable method is employed to introduce a scalar variable ?(x) that yield such condensate by means of its value in the vacuum, and then another auxiliary variable that corresponds to an antisymmetric gluon configuration ?(x). For that, besides that, two different possible limits of the fourth order non local quark interaction that may contribute to the NJL coupling are compared.
Toward an understanding of the $R_{AA}$ and $v_2$ puzzle for heavy quarks
Francesco Scardina; Santosh K Das; Salvatore Plumari; Jessica I. Bellone; Vincenzo Greco
2015-09-04
One of the primary aims of the ongoing nuclear collisions at Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) energies is to create a Quark Gluon Plasma (QGP). The heavy quarks constitutes a unique probe of the QGP properties. Both at RHIC and LHC energies a puzzling relation between the nuclear modification factor $R_{AA}(p_T)$ and the elliptic flow $v_2(p_T)$ related to heavy quark has been observed which challenged all the existing models.\\\\ We discuss how the temperature dependence of the heavy quark drag coefficient can address for a large part of such a puzzle. We have considered four different models to evaluate the temperature dependence of drag and diffusion coefficients propagating through a quark gluon plasma (QGP). All the four different models are set to reproduce the same $R_{AA}(p_T)$ experimentally observed at RHIC energy. We have found that for the same $R_{AA}(p_T)$ one can generate $2-3$ times more $v_{2}$ depending on the temperature dependence of the heavy quark drag coefficient.
Toward an understanding of the $R_{AA}$ and $v_2$ puzzle for heavy quarks
Scardina, Francesco; Plumari, Salvatore; Bellone, Jessica I; Greco, Vincenzo
2015-01-01
One of the primary aims of the ongoing nuclear collisions at Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) energies is to create a Quark Gluon Plasma (QGP). The heavy quarks constitutes a unique probe of the QGP properties. Both at RHIC and LHC energies a puzzling relation between the nuclear modification factor $R_{AA}(p_T)$ and the elliptic flow $v_2(p_T)$ related to heavy quark has been observed which challenged all the existing models.\\\\ We discuss how the temperature dependence of the heavy quark drag coefficient can address for a large part of such a puzzle. We have considered four different models to evaluate the temperature dependence of drag and diffusion coefficients propagating through a quark gluon plasma (QGP). All the four different models are set to reproduce the same $R_{AA}(p_T)$ experimentally observed at RHIC energy. We have found that for the same $R_{AA}(p_T)$ one can generate $2-3$ times more $v_{2}$ depending on the temperature dependence of the heavy quark drag...
Sambamurti Memorial Lecture: Spotlight on the Gluon
Michael Begelas
2010-09-01
Begel uses results from the Fermilab D0 and E706 experiments to explain how the production rate and energy spectrum of photons produced during proton collisions helped to clarify how the energy inside the proton is shared between quarks and gluons.
Strongly coupled plasma with electric and magnetic charges
Jinfeng Liao; Edward Shuryak
2006-12-12
A number of theoretical and lattice results lead us to believe that Quark-Gluon Plasma not too far from $T_c$ contains not only electrically charged quasiparticles -- quarks and gluons -- but magnetically charged ones -- monopoles and dyons -- as well. Although binary systems like charge-monopole and charge-dyon were considered in details before in both classical and quantum settings, it is the first study of coexisting electric and magnetic particles in many-body context. We perform Molecular Dynamics study of strongly coupled plasmas with $\\sim 1000$ particles and different fraction of magnetic charges. Correlation functions and Kubo formulae lead to such transport properties as diffusion constant, shear viscosity and electric conductivity: we compare the first two with empirical data from RHIC experiments as well as results from AdS/CFT correspondence. We also study a number of collective excitations in these systems.
Exotic hybrid mesons with light quarks
Claude Bernard; Tom Blum; Thomas A. DeGrand; Carleton DeTar; Steven Gottlieb; Urs. M. Heller; Jim Hetrick; Craig McNeile; Kari Rummukainen; Bob Sugar; Doug Toussaint; Matt Wingate
1996-07-12
Hybrid mesons, made from a quark, an antiquark and gluons, can have quantum numbers inaccessible to conventional quark-antiquark states. Confirmation of such states would give information on the role of "dynamical" color in low energy QCD. We present preliminary results for hybrid meson masses using light Wilson valence quarks.
An in-Medium Heavy-Quark Potential from the $Q\\bar{Q}$ Free Energy
Shuai Y. F. Liu; Ralf Rapp
2015-01-30
We investigate the problem of extracting a static potential between a quark and its antiquark in a quark-gluon plasma (QGP) from lattice-QCD computations of the singlet free energy, $F_{Q\\bar{Q}}(r)$. We utilize the thermodynamic $T$-matrix formalism to calculate the free energy from an underlying potential ansatz resummed in ladder approximation. Imaginary parts of both $Q\\bar Q$ potential-type and single-quark selfenergies are included as estimated from earlier results of the $T$-matrix approach. We find that the imaginary parts, and in particular their (low-) energy dependence, induce marked deviations of the (real part of the) potential from the calculated free energy. When fitting lattice results of the latter, the extracted potential is characterized by significant long-range contributions from remnants of the confining force. We briefly discuss consequences of this feature for the heavy-quark transport coefficient in the QGP.
Dynamical gluon mass and linear confinement
Ayala, Cesar; Vento, Vicente
2015-01-01
We define a non-perturbative running coupling in terms of a gluon mass function, similar to that used in some Dyson-Schwinger approaches. From this coupling, which satisfies asymptotic freedom and describes correctly the singularity structure of confinement, a static quark-antiquark potential is constructed. We calculate the bottomonium and charmonium spectra below the first open flavor meson-meson thresholds and show that for a small range of values of the free parameter determining the gluon mass function a good agreement with data is attained.
Gluon contribution to open heavy meson production in heavy-ion collisions
Cao, Shanshan; Wang, Xin-Nian
2015-01-01
A sizable contribution to heavy quark production in high-energy hadronic and nuclear collisions comes from heavy quark-antiquark pair production from gluon splitting during the parton shower evolution. We investigate the effect of gluon-medium interaction on open heavy flavor spectra in ultra-relativistic heavy-ion collisions. The interaction of hard gluons and heavy quarks with the hot QCD medium is simulated utilizing a Langevin transport model that simultaneously incorporates contributions from collisional and radiative processes. It is found that while the gluon splitting channel has quite important contribution to single D meson production cross section, its influence on the final heavy meson nuclear modification turns out to be quite modest due to the short average lifetime of hard gluons before splitting to heavy quark pairs during the evolution and propagation of the parton shower.
Quantum Chromodynamics Simulating Quarks and Gluons
Sugar, Robert
to understand matter at the smallest distance scales or largest energy scales. However, these fields impact and scientific importance of high energy and nuclear physics, the United States, the European Community and Japan are to: 1) verify the Standard Model of High Energy Physics, or discover its limits, 2) determine
Direct Probes of Linearly Polarized Gluons inside Unpolarized Hadrons
Boer, Daniel; /Groningen, KVI; Brodsky, Stanley J.; /SLAC /Southern Denmark U., CP3-Origins; Mulders, Piet J.; /Brussels U., IIHE; Pisano, Cristian; /Cagliari U. /INFN, Cagliari
2011-02-07
We show that the unmeasured distribution of linearly polarized gluons inside unpolarized hadrons can be directly probed in jet or heavy quark pair production both in electron-hadron and hadron-hadron collisions. We present expressions for the simplest cos 2{phi} asymmetries and estimate their maximal value in the particular case of electron-hadron collisions. Measurements of the linearly polarized gluon distribution in the proton should be feasible in future EIC or LHeC experiments.
Magnetic Fields Boosted by Gluon Vortices in Color Superconductivity
Efrain J. Ferrer; Vivian de la Incera
2006-08-28
We investigate the effects of an external magnetic field in the gluon dynamics of a color superconductor with three massless quark flavors. In the framework of gluon mean-field theory at asymptotic densities, we show that the long-range component $\\widetilde{H}$ of the external magnetic field that penetrates the CFL phase produces an instability when its strength becomes larger than the Meissner mass of the charged gluons. As a consequence, the magnetic field causes the formation of a vortex state characterized by the condensation of charged gluons and the creation of magnetic flux tubes. Inside the flux tubes the magnetic field is stronger than the applied one. This antiscreening effect is connected to the anomalous magnetic moment of the gluon field. We suggest how this same mechanism could serve to remove the chromomagnetic instabilities existing in gapless color superconductivity.
Quark Masses and Chiral Symmetry
Michael Creutz
1995-05-18
I discuss the global structure of the strongly interacting gauge theory of quarks and gluons as a function of the quark masses and the CP violating parameter $\\theta$. I concentrate on whether a first order phase transition occurs at $\\theta=\\pi.$ I show why this is expected when multiple flavors have a small degenerate mass. This transition can be removed by sufficient flavor-breaking. I speculate on the implications of this structure for Wilson's lattice fermions.
Quark condensate for various heavy flavors
Dmitri Antonov; Jose Emilio F. T. Ribeiro
2012-10-04
The quark condensate is calculated within the world-line effective-action formalism, by using for the Wilson loop an ansatz provided by the stochastic vacuum model. Starting with the relation between the quark and the gluon condensates in the heavy-quark limit, we diminish the current quark mass down to the value of the inverse vacuum correlation length, finding in this way a 64%-decrease in the absolute value of the quark condensate. In particular, we find that the conventional formula for the heavy-quark condensate cannot be applied to the c-quark, and that the corrections to this formula can reach 23% even in the case of the b-quark. We also demonstrate that, for an exponential parametrization of the two-point correlation function of gluonic field strengths, the quark condensate does not depend on the non-confining non-perturbative interactions of the stochastic background Yang-Mills fields.
Single top quark production at D0
Reinhard Schwienhorst; for the D0 collaboration
2011-09-13
Updates of electroweak single top quark production measurements by the D0 collaboration are presented using 5.4fb^-1 of proton-antiproton collision data from the Tevatron at Fermilab. Measurements of the t-channel, s-channel and combined single top quark production cross section are presented, including an updated lower limit on the CKM matrix element |V_tb|. Also reported are results from searches for gluon-quark flavor-changing neutral currents and W' boson production.
Dark matter and dark energy from quark bag model
Brilenkov, Maxim; Eingorn, Maxim; Jenkovszky, Laszlo; Zhuk, Alexander E-mail: maxim.eingorn@gmail.com E-mail: ai.zhuk2@gmail.com
2013-08-01
We calculate the present expansion of our Universe endowed with relict colored objects — quarks and gluons — that survived hadronization either as isolated islands of quark-gluon ''nuggets'' or spread uniformly in the Universe. In the first scenario, the QNs can play the role of dark matter. In the second scenario, we demonstrate that uniform colored objects can play the role of dark energy providing the late-time accelerating expansion of the Universe.
The effect of partonic wind on charm quark correlations in high-energy nuclear collisions
X. Zhu; N. Xu; P. Zhuang
2007-09-03
In high-energy collisions, massive heavy quarks are produced back-to-back initially and they are sensitive to early dynamical conditions. The strong collective partonic wind from the fast expanding quark-gluon plasma created in high-energy nuclear collisions modifies the correlation pattern significantly. As a result, the angular correlation function for D$\\bar{\\rm D}$ pairs is suppressed at the angle $\\Delta\\phi=\\pi$. While the hot and dense medium in collisions at RHIC ($\\sqrt{s_{NN}}=200$ GeV) can only smear the initial back-to-back D$\\bar {\\rm D}$ correlation, a clear and strong near side D$\\bar{\\rm D}$ correlation is expected at LHC ($\\sqrt{s_{NN}}=5500$ GeV).
Tensor gluons and proton structure
George Savvidy
2014-12-14
In a recent article we were considering a possibility that inside a proton and, more generally, inside hadrons there could be additional partons - tensor-gluons, which carry a part of the proton momentum. Tensor-gluons have zero electric charge, like gluons, but have a larger spin. Therefore we call them tensor-gluons. The nonzero density of tensor-gluons can be generated by the emission of tensor-gluons by gluons. Tensor-gluons can further split into the pairs of tensor-gluons through a different channels. To describe all these processes one should know the general splitting probabilities for tensor-gluons. These probabilities should fulfill very general symmetry relations, which we were able to resolve by introducing a splitting index. This approach allows to find out the general form of the splitting functions, to derive corresponding DGLAP evolution equations and to calculate the one-loop Callan-Simanzik beta function for tensor-gluons of a given spin. Our results provide a nontrivial consistency check of the theory and of the Callan-Simanzik beta function calculations, because the theory has a unique coupling constant and its high energy behavior should be universal for all particles of the spectrum. We argue that the contribution of all spins into the beta function vanishes leading to a conformal invariant theory at very high energies.
Probing the Linear Polarization of Gluons in Unpolarized Hadrons at EIC
Boer, Daniel; /Groningen, KVI; Brodsky, Stanley J.; /SLAC; Mulders, Piet J.; /Vrije U., Amsterdam; Pisano, Cristian; /Cagliari U. /INFN, Cagliari
2011-08-17
Gluons inside unpolarized hadrons can be linearly polarized provided they have a nonzero transverse momentum. The simplest and theoretically safest way to probe this TMD distribution of linearly polarized gluons is through cos 2{phi} asymmetries in heavy quark pair or dijet production in electron-hadron collisions. Future EIC or LHeC experiments are ideally suited for this purpose. Here we estimate the maximum asymmetries for EIC kinematics.
Static quark free energies at finite temperature with two flavors of improved Wilson quarks
Y. Maezawa; S. Ejiri; T. Hatsuda; N. Ishii; N. Ukita; S. Aoki; K. Kanaya
2006-10-02
Polyakov loop correlations at finite temperature in two-flavor QCD are studied in lattice simulations with the RG-improved gluon action and the clover-improved Wilson quark action. From the simulations on a $16^3 \\times 4$ lattice, we extract the free energies, the effective running coupling $g_{\\rm eff}(T)$ and the Debye screening mass $m_D(T)$ for various color channels of heavy quark--quark and quark--anti-quark pairs above the critical temperature. The free energies are well approximated by the screened Coulomb form with the appropriate Casimir factors. The magnitude and the temperature dependence of the Debye mass are compared to those of the next-to-leading order thermal perturbation theory and to a phenomenological formula given in terms of $g_{\\rm eff}(T)$. Also we made a comparison between our results with the Wilson quark and those with the staggered quark previously reported.
Liu, Fu-Hu; Lacey, Roy A
2015-01-01
Experimental results of the rapidity distributions of negatively charged pions produced in proton-proton (p-p) and beryllium-beryllium (Be-Be) collisions at different beam momentums, measured by the NA61/SHINE Collaboration at the super proton synchrotron (SPS), are described by a revised (three-source) Landau hydrodynamic model. The squared speed-of-sound parameter c^2_s is then extracted from the width of rapidity distribution. There is a knee point appearing at about 40A GeV/c (or 8.8 GeV) in the dependence of c^2_s on incident beam momentum (or center-of-mass energy). This knee point can be possibly regarded as the onset of deconfinement of the quarks and gluons in proton-proton collisions, and the critical point of phase transition from hadronic matter to quark-gluon plasma (QGP) in nucleus-nucleus collisions. It is possible that the quark deconfinement and QGP phase transition happen initially in collisions at 8.8 GeV.
Initial temperature and EoS of quark matter from direct photons
Mate Csanad; Imre Majer
2011-09-04
The time evolution of the quark gluon plasma created in gold-gold collisions of the Relativistic Heavy Ion Collider (RHIC) can be described by hydrodynamical models. Distribution of hadrons reflects the freeze-out state of the matter. To investigate the time evolution one needs to analyze penetrating probes, such as direct photon spectra. Distributions of low energy photons was published in 2010 by PHENIX. In this paper we analyze a 3+1 dimensional solution of relativistic hydrodynamics and calculate momentum distribution of direct photons. Using earlier fits of this model to hadronic spectra, we compare photon calculations to measurements and find that the initial temperature of the center of the fireball is at least 519+-12 MeV, while for the equation of state we get c_s= 0.36+-0.02.
Identification of Observables for Quark and Gluon Orbital Angular Momentum
Courtoy, Aurore; Hernandez, J Osvaldo Gonzalez; Liuti, Simonetta; Rajan, Abha
2014-01-01
A new debate has recently arisen on the subject of orbital angular momentum in QCD, in particular on its observability and on its partonic interpretation. Orbital momentum can be defined in QCD using two different decomposition schemes that yield a kinetic and a canonical definition, respectively. We argue that kinetic orbital angular momentum is intrinsically associated with twist three generalized parton distributions, and it is therefore more readily observable, while, due to parity constraints, canonical angular momentum, if defined as suggested in the literature in terms of generalized transverse momentum distributions, cannot be observed in scattering processes involving a single hadronic reaction plane.
Identification of Observables for Quark and Gluon Orbital Angular Momentum
Aurore Courtoy; Gary R. Goldstein; J. Osvaldo Gonzalez Hernandez; Simonetta Liuti; Abha Rajan
2014-12-01
A new debate has recently arisen on the subject of orbital angular momentum in QCD, in particular on its observability and on its partonic interpretation. Orbital momentum can be defined in QCD using two different decomposition schemes that yield a kinetic and a canonical definition, respectively. We argue that kinetic orbital angular momentum is intrinsically associated with twist three generalized parton distributions, and it is therefore more readily observable, while, due to parity constraints, canonical angular momentum, if defined as suggested in the literature in terms of generalized transverse momentum distributions, cannot be observed in scattering processes involving a single hadronic reaction plane.
Thermodynamics and geometry of strange quark matter
H. Gholizade; A. Altaibayeva; R. Myrzakulov
2014-12-21
We study thermodynamic of strange quark matter (SQM) using the analytic expressions of free and internal energies. We investigate two regimes of the high density and low density separately. As a vital program, in the case of a massless gluon and massless quarks at finite temperature, we also present a geometry of thermodynamics for the gluon and Bosons using a Legendre invariance metric, it is so called as geometrothermodynamic (GTD) to better understanding of the phase transition. The GTD metric and its second order scalar invariant have been obtained, and we clarify the phase transition by study the singularities of the scalar curvature of this Riemannian metric. This method is ensemble dependence and to complete the phase transition. Meanwhile, we also investigate enthalpy and entropy and internal energy representations. Our work exposes new pictures of the nature of phase transitions in SQM.
Search for pair production of excited top quarks in the lepton + jets final state
Apyan, Aram
A search is performed for pair-produced spin-3/2 excited top quarks (t[superscript ?][¯ over t][superscript ?]), each decaying to a top quark and a gluon. The search uses data collected with the CMS detector from pp ...
Production of b-quark jets at the large Hadron Collider in the parton-reggeization approach
Saleev, V. A. Shipilova, A. V.
2013-11-15
The inclusive hadroproduction of b-quark jets and bb-bar-quark dijets at the Large Hadron Collider is considered by using the hypothesis of gluon Reggeization in t-channel exchanges at high energies. Experimental data obtained by the ATLAS Collaboration are described well within all of the presented kinematical regions for single b-quark jets and bb-bar-quark dijets without resort to any free parameters.
Trace Anomaly and Dimension Two Gluon Condensate Above the Phase Transition
Megias,E.; Ruiz Arriola, E.; Salcedo, L.L.
2008-02-04
The dimension two gluon condensate has been used previously within a simple phenomenological model to describe power corrections from available lattice data for the renormalized Polyakov loop and the heavy quark-antiquark free energy in the deconfined phase of QCD. The QCD trace anomaly of gluodynamics also shows unequivocal inverse temperature power corrections which may be encoded as dimension two gluon condensate. We analyze lattice data of the trace anomaly and compare with other determinations of the condensate from previous references, yielding roughly similar numerical values.
An analysis of 4-quark energies in SU(2) lattice Monte Carlo
Sadataka Furui; Bilal Masud
1998-09-12
Energies of four-quark systems with the tetrahedral geometry measured by the static quenched SU(2) lattice Monte Carlo method are analyzed by parametrizing the gluon overlap factor in the form exp(-[bs EA+{\\sqrt bs}FP]) where A and P are the area and the perimeter defined mainly by the positions of the four quarks, bs is the string constant in the 2-quark potentials and E, F are constants.
Two-Photon, Two-gluon and Radiative Decays of Heavy Flavoured Mesons
Arpit Parmar; Bhavin Patel; P C Vinodkumar
2011-02-15
Here we present the two-photon and two-gluon decay widths of the S-wave ($\\eta_{Q\\in c,b}$) and P-wave ($\\chi_{Q\\in c,bJ}$) charmonium and bottonium states and the radiative transition decay widths of $c\\bar c$, $b\\bar b$ and $c\\bar b$ systems based on Coulomb plus power form of the inter-quark potential ($CPP_\
Simon Caron-Huot
2015-05-19
We propose the eikonal approximation as a simple and reliable tool to analyze relativistic high-energy processes, provided that the necessary subtleties are accounted for. An important subtlety is the need to include eikonal phases for a rapidity-dependent collection of particles, as embodied by the Balitsky-JIMWLK rapidity evolution equation. In the first part of this paper, we review how the phenomenon of gluon reggeization and the BFKL equations can be understood simply (but not too simply) in the eikonal approach. We also work out some previously overlooked implications of BFKL dynamics, including the observation that starting from four loops it is incompatible with a recent conjecture regarding the structure of infrared divergences. In the second part of this paper, we propose that in the strict planar limit the theory can be developed to all orders in the coupling with no reference at all to the concept of "reggeized gluon." Rather, one can work directly with a finite, process-dependent, number of Wilson lines. We demonstrate consistency of this proposal by an exact computation in N=4 super Yang-Mills, which shows that in processes mediated with two Wilson lines the reggeized gluon appears in the weak coupling limit as a resonance whose width is proportional to the coupling. We also provide a precise operator definition of Lipatov's integrable spin chain, which is manifestly integrable at any value of the coupling as a result of the duality between scattering amplitudes and Wilson loops in this theory.
Quark tensor charge and electric dipole moment within the Schwinger-Dyson formalism
Nodoka Yamanaka; Takahiro M. Doi; Shotaro Imai; Hideo Suganuma
2014-12-18
We calculate the tensor charge of the quark in the QCD-like theory in the Landau gauge using the Schwinger-Dyson formalism. It is found that the dressed tensor charge of the quark is significantly suppressed against the bare quark contribution, and the result agrees qualitatively with the analyses in the collinear factorization approach and lattice QCD. We also analyze the quark confinement effect with the phenomenological strong coupling given by Richardson, and find that this contribution is small. We show that the suppression of the quark tensor charge is due to the superposition of the spin flip of the quark arising from the successive emission of gluons which dress the tensor vertex. We also consider the relation between the quark and the nucleon electric dipole moments by combining with the simple constituent quark model.
Gasser, Juerg
2005-10-26
In my talk, I reviewed some basic aspects of quark masses: what do they mean, how can they be determined, what is our present knowledge on them. The talk was addressed to non specialists in the field, and so is this write up.
Chemical Potential Dependence of Chiral Quark Condensate in Dyson-Schwinger Equation Approach of QCD
Lei Chang; Huan Chen; Bin Wang; Wei Yuan; Yu-xin Liu
2006-11-06
We propose a chemical potential dependent effective gluon propagator and study the chiral quark condensate in strongly interacting matter in the framework of Dyson-Schwinger equation approach. The obtained results manifest that, as the effect of the chemical potential on the effective gluon propagator is taken into account, the chiral quark condensate decreases gradually with the increasing of the chemical potential if it is less than the critical value, and the condensate vanishes suddenly at the critical chemical potential. The inclusion of the chemical potential in the effective gluon propagator enhances the decreasing rate and decreases the critical chemical potential. It indicates that the chiral symmetry can be restored completely at a critical chemical potential and restored partially as the chemical potential is less than the critical value. If the effective gluon propagator is independent of the chemical potential, the chiral symmetry can only be restored suddenly but no gradual restoration.
Gluon Fusion Processes at One-loop within the Standard Model and Beyond
Ambresh Shivaji
2013-05-21
In this thesis, we have studied certain gluon fusion processes which proceed via quark loop diagrams at the leading order. The fact that these gluon-gluon channel processes are independent processes, their contributions towards the total/differential hadronic cross sections can be calculated separately. We have considered the production of a pair of electroweak vector bosons in association with a jet via gluon fusion within the standard model. These processes were not accessible at earlier hadron colliders such as the Tevatron. Therefore, observation of these rare processes at the LHC will be a test of the standard model itself. Like the di-vector boson production via gluon fusion processes, these processes are also important backgrounds for many new physics signals, and the standard model Higgs boson signal at the LHC. These leading order gluon fusion processes contribute to the corresponding hadronic processes at the next-to-next-to-leading order in {\\alpha}_s. We have taken a model of extra-dimensions, the ADD (Arkani-Hamed, Dimopoulos and Dvali) model, as the possible candidate of new physics at the LHC. This model tries to solve the hierarchy problem of the standard model by proposing large extra space dimensions which may be accessible at TeV scale. We have considered the direct production of KK-gravitons (GKK) in association with an electroweak boson (H/{\\gamma}/Z) via gluon fusion. These processes contribute to the corresponding hadronic processes at the next-to-leading order in {\\alpha}_s. Many interesting issues related to the fermion loop amplitudes have also been discussed.
Electric Flux Tube in Magnetic Plasma
Jinfeng Liao; Edward Shuryak
2007-12-06
In this paper we study a methodical problem related to the magnetic scenario recently suggested and initiated by the authors \\cite{Liao_ES_mono} to understand the strongly coupled quark-gluon plasma (sQGP): the electric flux tube in monopole plasma. A macroscopic approach, interpolating between Bose condensed (dual superconductor) and classical gas medium is developed first. Then we work out a microscopic approach based on detailed quantum mechanical calculation of the monopole scattering on electric flux tube, evaluating induced currents for all partial waves. As expected, the flux tube looses its stability when particles can penetrate it: we make this condition precise by calculating the critical value for the product of the flux tube size times the particle momentum, above which the flux tube dissolves. Lattice static potentials indicate that flux tubes seem to dissolve at $T>T_{dissolution} \\approx 1.3 T_c$. Using our criterion one gets an estimate of the magnetic density $n\\approx 4.4 \\sim 6.6 fm^{-3}$ at this temperature.
Sea Quark Flavor Asymmetry of Hadrons in Statistical Balance Model
Bin Zhang; Yong-Jun Zhang
2010-10-20
We derive a Menta Carlo method to simulate kinetic equilibrium ensemble, and get the same sea-quark flavor asymmetry as the linear equations method in statistical model. In the recent paper, we introduce the spilt factors to indicate the quarks' or gluons' spilt $g\\rightarrow q\\bar{q}(gg)$ and $q\\rightarrow qg$ ability. We obtain the almost fixed asymmetry value $0.12-0.16$ which consists with experimental measurements for proton, when the spilt factors vary in a very wide range over four orders of magnitude. So, we proof the sea quark asymmetry can be derived from statistic principle and not sensitively dependents on the dynamics details of quarks and gluons in proton. We also apply the Menta Carlo method of statistical model to predict the sea-quark asymmetry values for $K$ mesons, octet baryons $\\Sigma$,$\\Xi$ and $\\Delta$ baryons, even for exotic pentaquark states. All these asymmetry values just only dependent on the valence quarks numbers in those hadrons.
Abrikosov Gluon Vortices in Color Superconductors
Efrain J. Ferrer
2010-04-05
In this talk I will discuss how the in-medium magnetic field can influence the gluon dynamics in a three-flavor color superconductor. It will be shown how at field strengths comparable to the charged gluon Meissner mass a new phase can be realized, giving rise to Abrikosov's vortices of charged gluons. In that phase, the inhomogeneous gluon condensate anti-screens the magnetic field due to the anomalous magnetic moment of these spin-1 particles. This paramagnetic effect can be of interest for astrophysics, since due to the gluon vortex antiscreening mechanism, compact stars with color superconducting cores could have larger magnetic fields than neutron stars made up entirely of nuclear matter. I will also discuss a second gluon condensation phenomenon connected to the Meissner instability attained at moderate densities by two-flavor color superconductors. In this situation, an inhomogeneous condensate of charged gluons emerges to remove the chromomagnetic instability created by the pairing mismatch, and as a consequence, the charged gluonic currents induce a magnetic field. Finally, I will point out a possible relation between glitches in neutron stars and the existence of the gluon vortices.
Coulomb gluons and the ordering variable
René Ángeles-Martínez; Jeffrey R. Forshaw; Michael H. Seymour
2015-10-27
We study in detail the exchange of a Coulomb (Glauber) gluon in the first few orders of QCD perturbation theory in order to shed light on their accounting to all orders. We find an elegant cancellation of graphs that imposes a precise ordering on the transverse momentum of the exchanged Coulomb gluon.
Soft gluons are heavy and rowdy
Reinhard Alkofer; Pedro Bicudo; Stephen R. Cotanch; Christian S. Fischer; Felipe J. Llanes-Estrada
2006-01-10
We study dynamical mass generation in pure Yang-Mills theory and report on a recently developed ansatz that exactly solves the tower of Dyson-Schwinger equations in Landau gauge at low Euclidean momentum, featuring enhanced gluon-gluon vertices, a finite ghost-gluon vertex in agreement with an old argument of Taylor, and an IR suppressed gluon propagator. This ansatz reinforces arguments in favor of the concept of a gluon mass gap at low momentum (although the minimum of the gluon's dispersion relation is not at zero momentum). As an application, we have computed the spectrum of oddballs, three-gluon glueballs with negative parity and C-parity. The three body problem is variationally solved employing the color density-density interaction of Coulomb gauge QCD with a static Cornell potential. Like their even glueball counterparts, oddballs fall on Regge trajectories with similar slope to the pomeron. However their intercept at t=0 is smaller than the omega Regge trajectory and therefore the odderon may only be visible in experimental searches (for example at BNL) with higher -t than conducted to date at DESY.
Holographic Jets in an Expanding Plasma
Alexander Stoffers; Ismail Zahed
2012-11-19
We use the holographic principle to study quark jets with trailing strings in an expanding plasma that asymptotes Bjorken hydrodynamics. We make use of the fact that the trailing string is the locus of the light delay in bulk to obtain the explicit form for quark jets in the expanding plasma. From the trailing string solution we calculate the drag coefficient of a heavy quark in the strongly coupled expanding plasma. The energy scaling of the maximum penetration length of an ultrarelativistic light quark jet using light rays in bulk is estimated.
Unravelling an extended quark sector through multiple Higgs production?
Sally Dawson; Elisabetta Furlan; Ian Lewis
2014-10-16
In many new physics scenarios, the particle content of the Standard Model is extended and the Higgs couplings are modified, sometimes without affecting single Higgs production. We analyse two models with additional quarks. In these models, we compute double Higgs production from gluon fusion exactly at leading-order, and present analytical results in the heavy-quark mass ap- proximation. The experimental bounds from precision electroweak measurements and from the measured rate of single Higgs production combine to give significant restrictions for the allowed deviation of the double Higgs production rate from the Standard Model prediction as well as on the branching ratio for the Higgs decay into photons. The two models analysed eventually present a similar Higgs phenomenology as the Standard Model. We connect this result to the magnitude of the dimension six operators contributing to the gluon-fusion Higgs production.
Effects of quark chemical equilibration on thermal photon elliptic flow
Akihiko Monnai
2014-12-25
Large hadronic elliptic flow $v_2$ is considered as an evidence for the existence of a strongly-coupled QGP fluid in high-energy heavy-ion collisions. On the other hand, direct photon $v_2$ has recently been found to be much larger than hydrodynamic estimations, which is recognized as "photon $v_2$ puzzle". In this study, I discuss the implication of late production of quarks in an initially gluon-rich medium because photons are coupled to quarks. Numerical analyses imply that thermal photon $v_2$ can be visibly enhanced. This indicates that interplay of equilibration processes and collective expansion would be important.
Coulomb-gauge ghost and gluon propagators in SU(3) lattice Yang-Mills theory
Nakagawa, Y.; Toki, H. [Research Center for Nuclear Physics, Osaka University, Ibaraki-shi, Osaka 567-0047 (Japan); Voigt, A. [Humboldt-Universitaet zu Berlin, Institut fuer Physik, D-12489 Berlin (Germany); Max-Planck-Institut fuer Meteorologie, D-20146 Hamburg (Germany); Ilgenfritz, E.-M. [Humboldt-Universitaet zu Berlin, Institut fuer Physik, D-12489 Berlin (Germany); Karl-Franzens-Universitaet Graz, Institut fuer Physik, A-8010 Graz (Austria); Mueller-Preussker, M. [Humboldt-Universitaet zu Berlin, Institut fuer Physik, D-12489 Berlin (Germany); Nakamura, A. [Research Institute for Information Science and Education, Hiroshima University, Higashi-Hiroshima 739-8521 (Japan); Saito, T. [Integrated Information Center, Kochi University, Akebono-cho, Kochi 780-8520 (Japan); Sternbeck, A. [CSSM, School of Chemistry and Physics, University of Adelaide, SA 5005 (Australia)
2009-06-01
We study the momentum dependence of the ghost propagator and of the space and time components of the gluon propagator at equal time in pure SU(3) lattice Coulomb-gauge theory carrying out a joint analysis of data collected independently at the Research Center for Nuclear Physics, Osaka and Humboldt University, Berlin. We focus on the scaling behavior of these propagators at {beta}=5.8,...,6.2 and apply a matching technique to relate the data for the different lattice cutoffs. Thereby, lattice artifacts are found to be rather strong for both instantaneous gluon propagators at a large momentum. As a byproduct we obtain the respective lattice scale dependences a({beta}) for the transversal gluon and the ghost propagator which indeed run faster with {beta} than two-loop running, but slightly slower than what is known from the Necco-Sommer analysis of the heavy quark potential. The abnormal a({beta}) dependence as determined from the instantaneous time-time gluon propagator, D{sub 44}, remains a problem, though. The role of residual gauge-fixing influencing D{sub 44} is discussed.
Electric and magnetic screenings of gluons in a model with dimension-2 gluon condensate
Fukun Xu; Mei Huang
2011-11-22
Electric and magnetic screenings of the thermal gluons are studied by using the background expansion method in a gluodynamic model with dimension-2 gluon condensate. At low temperature, the electric and magnetic gluons are degenerate. With the increasing of temperature, it is found that the electric and magnetic gluons start to split at certain temperature $T_0$. The electric screening mass changes rapidly with temperature when $T>T_0$, and the Polyakov loop expectation value rises sharply around $T_0$ from zero in the vacuum to a value around 0.8 at high temperature. This suggests that the color electric deconfinement phase transition is driven by electric gluons. It is also observed that the magnetic screening mass keeps almost the same as its vacuum value, which manifests that the magnetic gluons remains confined. Both the screening masses and the Polyakov loop results are qualitatively in agreement with the Lattice calculations.
Gluons in our future | Jefferson Lab
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Gluons in our future July 30, 2014 If one were to eavesdrop on the conversations that we have with our visitors - students of all kinds, politicians or the general public - one...
Basic features of the pion valence-quark distribution function
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Chang, Lei; Mezrag, Cédric; Moutarde, Hervé; Roberts, Craig D.; Rodríguez-Quintero, Jose; Tandy, Peter C.
2014-10-07
The impulse-approximation expression used hitherto to define the pion's valence-quark distribution function is flawed because it omits contributions from the gluons which bind quarks into the pion. A corrected leading-order expression produces the model-independent result that quarks dressed via the rainbow–ladder truncation, or any practical analogue, carry all the pion's light-front momentum at a characteristic hadronic scale. Corrections to the leading contribution may be divided into two classes, responsible for shifting dressed-quark momentum into glue and sea-quarks. Working with available empirical information, we use an algebraic model to express the principal impact of both classes of corrections. This enables amore »realistic comparison with experiment that allows us to highlight the basic features of the pion's measurable valence-quark distribution, q?(x); namely, at a characteristic hadronic scale, q?(x)~(1-x)2 for x?0.85; and the valence-quarks carry approximately two-thirds of the pion's light-front momentum.« less
Yannis Burnier; Olaf Kaczmarek; Alexander Rothkopf
2014-11-12
We report recent results of a non-perturbative determination of the static heavy-quark potential in quenched and dynamical lattice QCD at finite temperature. The real and imaginary part of this complex quantity are extracted from the spectral function of Wilson line correlators in Coulomb gauge. To obtain spectral information from Euclidean time numerical data, our study relies on a novel Bayesian prescription that differs from the Maximum Entropy Method. We perform simulations on quenched $32^3\\times N_\\tau$ $(\\beta=7.0,\\xi=3.5)$ lattices with $N_\\tau=24,...,96$, which cover $839{\\rm MeV} \\geq T\\geq 210 {\\rm MeV}$. To investigate the potential in a quark-gluon plasma with light u,d and s quarks we utilize $N_f=2+1$ ASQTAD lattices with $m_l=m_s/20$ by the HotQCD collaboration, giving access to temperatures between $286 {\\rm MeV} \\geq T\\geq 148{\\rm MeV}$. The real part of the potential exhibits a clean transition from a linear, confining behavior in the hadronic phase to a Debye screened form above deconfinement. Interestingly its values lie close to the color singlet free energies in Coulomb gauge at all temperatures. We estimate the imaginary part on quenched lattices and find that it is of the same order of magnitude as in hard-thermal loop perturbation theory. From among all the systematic checks carried out in our study, we discuss explicitly the dependence of the result on the default model and the number of datapoints.
The effects of colored quark entropy on the bag pressure
Miller, David E
2004-01-01
We study the effects of the ground state entropy of colored quarks upon the bag pressure at low temperatures. The vacuum expectation values of the quark and gluon fields are used to express the interactions in QCD ground state in the limit of low temperatures and chemical potentials. Apparently, the inclusion of this entropy in the equation of state provides the hadron constituents with an additional heat which causes a decrease in the effective latent heat inside the hadronic bag and consequently decreases the non-perturbative bag pressure. We have considered two types of baryonic bags, $\\Delta$ and $\\Omega^-$. In both cases we have found that the bag pressure decreases with the temperature. On the other hand, when the colored quark ground state entropy is not considered, the bag pressure as conventionally believed remains constant for finite temperature.
Thermalization of gluon matter including ggggg interactions
A. El; C. Greiner; Z. Xu
2006-09-27
Within a pQCD inspired kinetic parton cascade we simulate the space time evolution of gluons which are produced initially in a heavy ion collision at RHIC energy. The inelastic gluonic interactions $gg \\leftrightarrow ggg$ do play an important role: For various initial conditions it is found that thermalization and the close to ideal fluid dynamical behaviour sets in at very early times. Special emphasis is put on color glass condensate initial conditions and the `bottom up thermalization' scenario. Off-equilibrium $3\\to 2$ processes make up the very beginning of the evolution leading to an initial decrease in gluon number and a temporary avalanche of the gluon momentum distribution to higher transversal momenta.
Higgs boson plus photon production at the LHC: a clean probe of the b-quark parton densities
Emidio Gabrielli; Barbara Mele; Johan Rathsman
2007-12-04
Higgs boson production in association with a high pT photon at the CERN Large Hadron Collider is analyzed, in the framework of the MSSM model, for the heavier neutral Higgs bosons. The request of an additional photon in the exclusive Higgs boson final state selects b-quark pairs among the possible initial partonic states, since gluon-gluon initial states are not allowed by C-parity conservation. Hence, the measurement of cross sections for neutral Higgs boson plus photon production can provide a clean probe of the b-quark density in the proton as well as of the b-quark Yukawa coupling. The suppression of the production rates by the b-quark electromagnetic coupling can be compensated by the enhanced Higgs boson Yukawa coupling to b's in the large tan(beta) regime. The Higgs boson decay into a tau-lepton pair is considered, and irreducible backgrounds with corresponding signal significances are evaluated.
Y. Maezawa; S. Aoki; S. Ejiri; T. Hatsuda; K. Kanaya; H. Ohno; T. Umeda
2009-11-02
The free energy between a static quark and an antiquark is studied by using the color-singlet Polyakov-line correlation at finite temperature. We perform simulations on $32^3 \\times 12$, 10, 8, 6, 4 lattices in the high temperature phase with the RG-improved gluon action and 2+1 flavors of the clover-improved Wilson quark action. Since the simulations are based on the fixed scale approach that the temperature can be varied without changing the spatial volume and renormalization factor, it is possible to investigate temperature dependence of the heavy-quark free energy without any adjustment of the overall constant. We find that, the heavy-quark free energies at short distance converge to the heavy-quark potential evaluated from the Wilson-loop operator at zero temperature, in accordance with the expected insensitivity of short distance physics to the temperature. At long distance, the heavy-quark free energies approach to twice the single-quark free energies, implying that the interaction between heavy quarks is screened. The Debye screening mass obtained from the long range behavior of the heavy-quark free energy is compared with results of the thermal perturbation theory and those of $N_f=2$ and $N_f=0$ lattice simulations.
The Specific Heat of Normal, Degenerate Quark Matter: Non-Fermi Liquid Corrections
Daniel Boyanovsky; H. J. de Vega
2001-02-26
In normal degenerate quark matter, the exchange of dynamically screened transverse gluons introduces infrared divergences in the quark self-energies that lead to the breakdown of the Fermi liquid description. If the core of neutron stars are composed of quark matter with a normal component, cooling by direct quark Urca processes may be modified by non-Fermi liquid corrections. We find that while the quasiparticle density of states is finite and non-zero at the Fermi surface, its frequency derivative diverges and results in non-Fermi liquid corrections to the specific heat of the normal, degenerate component of quark matter. We study these non-perturbative non-Fermi liquid corrections to the specific heat and the temperature dependence of the chemical potential and show that these lead to a reduction of the specific heat.
Strange quark matter in strong magnetic fields within a confining model
Monika Sinha; Xu-Guang Huang; Armen Sedrakian
2013-08-01
We construct an equation of state of strange quark matter in strong magnetic field within a confining model. The confinement is modeled by means of the Richardson potential for quark-quark interaction modified suitably to account for strong magnetic field. We compare our results for the equation of state and magnetization of matter to those derived within the MIT bag model. The differences between these models arise mainly due to the momentum dependence of the strong interaction between quarks in the Richardson model. Specifically, we find that the magnetization of strange quark matter in this model has much more pronounced de Haas-van Alf\\'{v}en oscillations than in the MIT bag model, which is the consequence of the (static) gluon-exchange structure of the confining potential.
Gluon Condensate in Pion Superfluid beyond Mean Field Approximation
Yin Jiang; Pengfei Zhuang
2011-03-04
We study gluon condensate in a pion superfluid, through calculating the equation of state of the system in the Nambu-Jona-Lasinio model. While in mean field approximation the growing pion condensate leads to an increasing gluon condensate, meson fluctuations reduce the gluon condensate and the broken scalar symmetry can be smoothly restored at finite isospin density.
Extracting gluon condensate from the average plaquette
Taekoon Lee
2015-03-27
The perturbative contribution in the average plaquette is subtracted using Borel summation and the remnant of the plaquette is shown to scale as a dim-4 condensate. A critical review is presented of the renormalon subtraction scheme that claimed a dim-2 condensate. The extracted gluon condensate is compared with the latest result employing high order (35-loop) calculation in the stochastic perturbation theory.
A General Effective Action for Quark Matter and its Application to Color Superconductivity
Philipp T. Reuter
2006-02-13
I derive a general effective theory for hot and/or dense quark matter. After introducing general projection operators for hard and soft quark and gluon degrees of freedom, I explicitly compute the functional integral for the hard quark and gluon modes in the QCD partition function. Upon appropriate choices for the projection operators one recovers various well-known effective theories such as the Hard Thermal Loop/ Hard Dense Loop Effective Theories as well as the High Density Effective Theory by Hong and Schaefer. I then apply the effective theory to cold and dense quark matter and show how it can be utilized to simplify the weak-coupling solution of the color-superconducting gap equation. In general, one considers as relevant quark degrees of freedom those within a thin layer of width 2 Lambda_q around the Fermi surface and as relevant gluon degrees of freedom those with 3-momenta less than Lambda_gl. It turns out that it is necessary to choose Lambda_q << Lambda_gl, i.e., scattering of quarks along the Fermi surface is the dominant process. Moreover, this special choice of the two cutoff parameters Lambda_q and Lambda_gl facilitates the power-counting of the numerous contributions in the gap-equation. In addition, it is demonstrated that both the energy and the momentum dependence of the gap function has to be treated self-consistently in order to determine the imaginary part of the gap function. For quarks close to the Fermi surface the imaginary part is calculated explicitly and shown to be of sub-subleading order in the gap equation.
WHOT-QCD Collaboration; :; Y. Maezawa; N. Ukita; S. Aoki; S. Ejiri; T. Hatsuda; N. Ishii; K. Kanaya
2007-02-13
We study Polyakov loop correlations and spatial Wilson loop at finite Temperature in two-flavor QCD simulations with the RG-improved gluon action and the clover-improved Wilson quark action on a $ 16^3 \\times 4$ lattice. From the line of constant physics at $m_{\\rm PS}/m_{\\rm V}=0.65$ and 0.80, we extract the heavy-quark free energies, the effective running coupling $g_{\\rm eff}(T)$ and the Debye screening mass $m_D(T)$ for various color channels of heavy quark--quark and quark--anti-quark pairs above the critical temperature. The free energies are well approximated by the screened Coulomb form with the appropriate Casimir factors at high temperature. The magnitude and the temperature dependence of the Debye mass are compared to those of the next-to-leading order thermal perturbation theory and to a phenomenological formula in terms of $g_{\\rm eff}(T)$. We make a comparison between our results with the Wilson quark action and the previous results with the staggered quark action. The spatial string tension is also studied in the high temperature phase and is compared to the next-to-next-leading order prediction in an effective theory with dimensional reduction.
Search for a heavy vector boson decaying to two gluons in pp? collisions at ?s=1.96 TeV
Aaltonen, T.; Adelman, J.; Álvarez González, B.; Amerio, S.; Amidei, D.; Anastassov, A.; Annovi, A.; Antos, J.; Apollinari, G.; Appel, J. A.; Arisawa, T.; Artikov, A.; Asaadi, J.; Ashmanskas, W.; Auerbach, B.; Aurisano, A.; Azfar, F.; Badgett, W.; Bae, T.; Barbaro-Galtieri, A.; Barnes, V. E.; Barnett, B. A.; Barria, P.; Bartos, P.; Bauce, M.; Bedeschi, F.; Behari, S.; Bellettini, G.; Bellinger, J.; Benjamin, D.; Beretvas, A.; Bhatti, A.; Bisello, D.; Bizjak, I.; Bland, K. R.; Blumenfeld, B.; Bocci, A.; Bodek, A.; Bortoletto, D.; Boudreau, J.; Boveia, A.; Brigliadori, L.; Bromberg, C.; Brucken, E.; Budagov, J.; Budd, H. S.; Burkett, K.; Busetto, G.; Bussey, P.; Buzatu, A.; Calamba, A.; Calancha, C.; Camarda, S.; Campanelli, M.; Campbell, M.; Canelli, F.; Carls, B.; Carlsmith, D.; Carosi, R.; Carrillo, S.; Carron, S.; Casal, B.; Casarsa, M.; Castro, A.; Catastini, P.; Cauz, D.; Cavaliere, V.; Cavalli-Sforza, M.; Cerri, A.; Cerrito, L.; Chen, Y. C.; Chertok, M.; Chiarelli, G.; Chlachidze, G.; Chlebana, F.; Cho, K.; Chokheli, D.; Chung, W. H.; Chung, Y. S.; Ciocci, M. A.; Clark, A.; Clarke, C.; Compostella, G.; Convery, M. E.; Conway, J.; Corbo, M.; Cordelli, M.; Cox, C. A.; Cox, D. J.; Crescioli, F.; Cuevas, J.; Culbertson, R.; Dagenhart, D.; d’Ascenzo, N.; Datta, M.; de Barbaro, P.; Dell’Orso, M.; Demortier, L.; Deninno, M.; Devoto, F.; d’Errico, M.; Di Canto, A.; Di Ruzza, B.; Dittmann, J. R.; D’Onofrio, M.; Donati, S.; Dong, P.; Dorigo, M.; Dorigo, T.; Ebina, K.; Elagin, A.; Eppig, A.; Erbacher, R.; Errede, S.; Ershaidat, N.; Eusebi, R.; Farrington, S.; Feindt, M.; Fernandez, J. P.; Field, R.; Flanagan, G.; Forrest, R.; Frank, M. J.; Franklin, M.; Freeman, J. C.; Funakoshi, Y.; Furic, I.; Gallinaro, M.; Garcia, J. E.; Garfinkel, A. F.; Garosi, P.; Gerberich, H.; Gerchtein, E.; Giagu, S.; Giakoumopoulou, V.; Giannetti, P.; Gibson, K.; Ginsburg, C. M.; Giokaris, N.; Giromini, P.; Giurgiu, G.; Glagolev, V.; Glenzinski, D.; Gold, M.; Goldin, D.; Goldschmidt, N.; Golossanov, A.; Gomez, G.; Gomez-Ceballos, G.; Goncharov, M.; González, O.; Gorelov, I.; Goshaw, A. T.; Goulianos, K.; Grinstein, S.; Grosso-Pilcher, C.; Group, R. C.; Guimaraes da Costa, J.; Hahn, S. R.; Halkiadakis, E.; Hamaguchi, A.; Han, J. Y.; Happacher, F.; Hara, K.; Hare, D.; Hare, M.; Harr, R. F.; Hatakeyama, K.; Hays, C.; Heck, M.; Heinrich, J.; Herndon, M.; Hewamanage, S.; Hocker, A.; Hopkins, W.; Horn, D.; Hou, S.; Hughes, R. E.; Hurwitz, M.; Husemann, U.; Hussain, N.; Hussein, M.; Huston, J.; Introzzi, G.; Iori, M.; Ivanov, A.; James, E.; Jang, D.; Jayatilaka, B.; Jeon, E. J.; Jindariani, S.; Jones, M.; Joo, K. K.; Jun, S. Y.; Junk, T. R.; Kamon, T.; Karchin, P. E.; Kasmi, A.; Kato, Y.; Ketchum, W.; Keung, J.; Khader, M.; Khotilovich, V.; Kilminster, B.; Kim, D. H.; Kim, H. S.; Kim, J. E.; Kim, M. J.; Kim, S. B.; Kim, S. H.; Kim, Y. K.; Kim, Y. J.; Kimura, N.; Kirby, M.; Klimenko, S.; Knoepfel, K.; Kondo, K.; Kong, D. J.; Konigsberg, J.; Kotwal, A. V.; Kreps, M.; Kroll, J.; Krop, D.; Kruse, M.; Krutelyov, V.; Kuhr, T.; Kurata, M.; Kwang, S.; Laasanen, A. T.; Lami, S.; Lammel, S.; Lancaster, M.; Lander, R. L.; Lannon, K.; Lath, A.; Latino, G.; LeCompte, T.; Lee, E.; Lee, H. S.; Lee, J. S.; Lee, S. W.; Leo, S.; Leone, S.; Lewis, J. D.; Limosani, A.; Lin, C.-J.; Lindgren, M.; Lipeles, E.; Lister, A.; Litvintsev, D. O.; Liu, C.; Liu, H.; Liu, Q.; Liu, T.; Lockwitz, S.; Loginov, A.; Lucchesi, D.; Lueck, J.; Lujan, P.; Lukens, P.; Lungu, G.; Lys, J.; Lysak, R.; Madrak, R.; Maeshima, K.; Maestro, P.; Malik, S.; Manca, G.; Manousakis-Katsikakis, A.; Margaroli, F.; Marino, C.; Martínez, M.; Mastrandrea, P.; Matera, K.; Mattson, M. E.; Mazzacane, A.; Mazzanti, P.; McFarland, K. S.; McIntyre, P.; McNulty, R.; Mehta, A.; Mehtala, P.; Mesropian, C.; Miao, T.; Mietlicki, D.; Mitra, A.; Miyake, H.; Moed, S.; Moggi, N.; Mondragon, M. N.; Moon, C. S.; Moore, R.; Morello, M. J.; Morlock, J.; Movilla Fernandez, P.; Mukherjee, A.; Muller, Th.; Murat, P.; Mussini, M.; Nachtman, J.; Nagai, Y.; Naganoma, J.; Nakano, I.; Napier, A.; Nett, J.; Neu, C.; Neubauer, M. S.; Nielsen, J.; Nodulman, L.; Noh, S. Y.; Norniella, O.; Oakes, L.; Oh, S. H.; Oh, Y. D.; Oksuzian, I.; Okusawa, T.; Orava, R.; Ortolan, L.; Pagan Griso, S.; Pagliarone, C.; Palencia, E.; Papadimitriou, V.; Paramonov, A. A.; Patrick, J.; Pauletta, G.; Paulini, M.; Paus, C.; Pellett, D. E.; Penzo, A.; Phillips, T. J.; Piacentino, G.; Pianori, E.; Pilot, J.; Pitts, K.; Plager, C.; Pondrom, L.; Poprocki, S.; Potamianos, K.; Prokoshin, F.; Pranko, A.; Ptohos, F.; Punzi, G.; Rahaman, A.; Ramakrishnan, V.; Ranjan, N.; Rao, K.; Redondo, I.; Renton, P.; Rescigno, M.; Riddick, T.; Rimondi, F.; Ristori, L.; Robson, A.; Rodrigo, T.; Rodriguez, T.; Rogers, E.; Rolli, S.; Roser, R.; Ruffini, F.; Ruiz, A.; Russ, J.; Rusu, V.
2012-12-01
We present a search for a new heavy vector boson Z' that decays to gluons. Decays to on-shell gluons are suppressed, leading to a dominant decay mode of Z'?g*g. We study the case where the off-shell gluon g* converts to a pair of top quarks, leading to a final state of tt¯g. In a sample of events with exactly one charged lepton, large missing transverse momentum and at least five jets, corresponding to an integrated luminosity of 8.7 fb?¹ collected by the CDF II detector, we find the data to be consistent with the standard model. We set upper limits on the production cross section times branching ratio of this chromophilic Z' at 95% confidence level from 300 to 40 fb for Z' masses ranging from 400 to 1000 GeV/c², respectively.
Search for a heavy vector boson decaying to two gluons in pp? collisions at ?s=1.96 TeV
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Aaltonen, T.; Adelman, J.; Álvarez González, B.; Amerio, S.; Amidei, D.; Anastassov, A.; Annovi, A.; Antos, J.; Apollinari, G.; Appel, J. A.; et al
2012-12-05
We present a search for a new heavy vector boson Z' that decays to gluons. Decays to on-shell gluons are suppressed, leading to a dominant decay mode of Z'?g*g. We study the case where the off-shell gluon g* converts to a pair of top quarks, leading to a final state of tt¯g. In a sample of events with exactly one charged lepton, large missing transverse momentum and at least five jets, corresponding to an integrated luminosity of 8.7 fb?¹ collected by the CDF II detector, we find the data to be consistent with the standard model. We set upper limitsmore »on the production cross section times branching ratio of this chromophilic Z' at 95% confidence level from 300 to 40 fb for Z' masses ranging from 400 to 1000 GeV/c², respectively.« less
Tomomi Ishikawa; Yasumichi Aoki; Jonathan M. Flynn; Taku Izubuchi; Oleg Loktik
2011-05-16
We discuss perturbative O(g^2a) matching with static heavy quarks and domain-wall light quarks for lattice operators relevant to B-meson decays and $B^0$-$\\bar{B}^0$ mixing. The chiral symmetry of the light domain-wall quarks does not prohibit operator mixing at O(a) for these operators. The O(a) corrections to physical quantities are non-negligible and must be included to obtain high-precision simulation results for CKM physics. We provide results using plaquette, Symanzik, Iwasaki and DBW2 gluon actions and applying APE, HYP1 and HYP2 link-smearing for the static quark action.
Erich W. Varnes
2008-10-20
A review is presented of the current experimental status of the top quark sector of the standard model. The measurements summarized include searches for electroweak single top production, the latest results on the ttbar production cross section, and searches for new physics in top quark production and decay. In addition, the recent measurement of the top quark mass to a precision of 0.7% is highlighted
Tai An; Sa Ben-Hao
1998-04-01
The idea that effective string tension increases as a result of the hard gluon kinks on a string is applied to study the strange particle production in proton-nucleus and nucleus-nucleus collisions. It is found that the effective string tension increases with the increase of centrality and mass of the colliding system as a consequence of the mini-(gluon)jet production stemming from the collective string-string interaction. This mechanism leads to strangeness enhancement in pA and AA collisions through the enhanced production of the strange quark pairs from the color field of strings. We discuss different roles played by this mechanism and rescattering of the final state hadrons in the production of strange particles and compare our results with experimental data.
Sketching the pion's valence-quark generalised parton distribution
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Mezrag, C.; Chang, L.; Moutarde, H.; Roberts, C. D.; Rodríguez-Quintero, J.; Sabatié, F.; Schmidt, S. M.
2015-02-01
In order to learn effectively from measurements of generalised parton distributions (GPDs), it is desirable to compute them using a framework that can potentially connect empirical information with basic features of the Standard Model. We sketch an approach to such computations, based upon a rainbow-ladder (RL) truncation of QCD’s Dyson–Schwinger equations and exemplified via the pion’s valence dressed-quark GPD, Hv?(x, ?, t). Our analysis focuses primarily on ?=0, although we also capitalise on the symmetry-preserving nature of the RL truncation by connecting Hv?(x, ?=±1, t)with the pion’s valence-quark parton distribution amplitude. We explain that the impulse-approximation used hitherto to definemore »the pion’s valence dressed-quark GPD is generally invalid owing to omission of contributions from the gluons which bind dressed-quarks into the pion. A simple correction enables us to identify a practicable improvement to the approximation for Hv?(x, 0, t), expressed as the Radon transform of a single amplitude. Therewith we obtain results for Hv?(x, 0, t) and the associated impact-parameter dependent distribution, qv?(x, |b?|), which provide a qualitatively sound picture of the pion’s dressed-quark structure at a hadronic scale. We evolve the distributions to a scale ? = 2 GeV, so as to facilitate comparisons in future with results from experiment or other nonperturbative methods.« less
Eric Laenen
2008-09-18
I review how the top quark is embedded in the Standard Model and some its proposed extensions, and how it manifests itself in various hadron collider signals.
Multi-Quark Energies in SU(2) Lattice Gauge Theory
A. M. Green; C. Michael; J. E. Paton; M. E. Sainio
1993-01-15
Energies of four-quark systems have been extracted in a quenched SU(2) lattice Monte Carlo calculation for two different geometries, rectangular and colinear, with $\\beta=2.4$ and lattice size $16^3\\times 32$. Also, by going to a lattice $24^3\\times 32$ and to $\\beta=2.5$, the effect of the finite lattice size and scaling are checked. An attempt is made to understand these results in terms of a model based on interquark two-body potentials but modified very significantly by a phenomenological gluon-field overlap factor.
Continuum extrapolation of energies of a four-quark system in lattice gauge theory
Petrus Pennanen
1997-01-12
A continuum extrapolation of static two- and four-quark energies calculated in quenched SU(2) lattice Monte Carlo is carried out based on Sommer's method of setting the scale. The beta-function is obtained as a side product of the extrapolations. Four-quark binding energies are found to be essentially constant at beta >= 2.35 unlike the two-body potentials. A model for four-quark energies, with explicit gluonic degrees of freedom removed, is fitted to these energies and the behaviour of the parameters of the model is investigated. An extension of the model using the first excited states of the two-body gluon field as additional basis states is found to be necessary for quarks at the corners of regular tetrahedra.
Higgs boson pair production: top quark mass effects at NLO and NNLO
Grigo, Jonathan; Steinhauser, Matthias
2015-01-01
We compute next-to-next-to-leading order QCD corrections to the gluon-induced production cross section of Higgs boson pairs in the large top quark mass limit using the soft-virtual approximation. In the limit of infinitely-heavy top quark we confirm the results in the literature. We add two more expansion terms in the inverse top quark mass to the $M_t\\to\\infty$ result. Since the $1/M_t$ expansion converges poorly, we try to improve on it by factorizing the exact leading order cross section. We discuss two ways of doing that and conclude that the finite top quark mass effects shift the cross section at most by about 10\\% at next-to-leading order and by about 5\\% at next-to-next-to-leading order.
Quantum chromodynamics quark benzene
Jialun Ping; Chengrong Deng; Fan Wang; T. Goldman
2007-11-28
A six-quark state with the benzene-like structure is proposed and studied based on color string model. The calculation with the quadratic confinement show that such structure has the lowest energy among the various hidden color six-quark structures proposed so far. Its possible effect on $NN$ scattering is discussed.
Forward-backward asymmetry in top quark-antiquark production
Abazov, Victor Mukhamedovich [Dubna, JINR; Abbott, Braden Keim [Oklahoma U.; Acharya, Bannanje Sripath [Tata Inst.; Adams, Mark Raymond [Illinois U., Chicago; Adams, Todd [Florida State U.; Alexeev, Guennadi D [Dubna, JINR; Alkhazov, Georgiy D [St. Petersburg, INP; Alton, Andrew K [Michigan U.; Augustana Coll., Sioux Falls; Alverson, George O [Northeastern U.; Alves, Gilvan Augusto [Rio de Janeiro, CBPF; Aoki, Masato [Fermilab; Louisiana Tech. U.
2011-12-12
We present a measurement of forward-backward asymmetry in top quark-antiquark production in proton-antiproton collisions in the final state containing a lepton and at least four jets. Using a dataset corresponding to an integrated luminosity of 5.4 fb^{-1}, collected by the D0 experiment at the Fermilab Tevatron Collider, we measure the t{bar t} forward-backward asymmetry to be (9.2 ± 3.7)% at the reconstruction level. When corrected for detector acceptance and resolution, the asymmetry is found to be (19.6 ± 6.5)%. We also measure a corrected asymmetry based on the lepton from a top quark decay, found to be (15.2 ± 4.0)%. The results are compared to predictions based on the next-to-leading-order QCD generator mc@nlo. The sensitivity of the measured and predicted asymmetries to the modeling of gluon radiation is discussed.
Forward-backward asymmetry in top quark-antiquark production
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Abazov, Victor Mukhamedovich [Dubna, JINR; Abbott, Braden Keim [Oklahoma U.; Acharya, Bannanje Sripath [Tata Inst.; Adams, Mark Raymond [Illinois U., Chicago; Adams, Todd [Florida State U.; Alexeev, Guennadi D [Dubna, JINR; Alkhazov, Georgiy D [St. Petersburg, INP; Alton, Andrew K [Michigan U.; Augustana Coll., Sioux Falls; Alverson, George O [Northeastern U.; Alves, Gilvan Augusto [Rio de Janeiro, CBPF; Aoki, Masato [Fermilab; Louisiana Tech. U.
2011-12-12
We present a measurement of forward-backward asymmetry in top quark-antiquark production in proton-antiproton collisions in the final state containing a lepton and at least four jets. Using a dataset corresponding to an integrated luminosity of 5.4 fb-1, collected by the D0 experiment at the Fermilab Tevatron Collider, we measure the t{bar t} forward-backward asymmetry to be (9.2 ± 3.7)% at the reconstruction level. When corrected for detector acceptance and resolution, the asymmetry is found to be (19.6 ± 6.5)%. We also measure a corrected asymmetry based on the lepton from a top quark decay, found to be (15.2 ± 4.0)%. The results are compared to predictions based on the next-to-leading-order QCD generator mc@nlo. The sensitivity of the measured and predicted asymmetries to the modeling of gluon radiation is discussed.
Forward-backward asymmetry in top quark-antiquark production
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Abazov, Victor Mukhamedovich
2011-12-12
We present a measurement of forward-backward asymmetry in top quark-antiquark production in proton-antiproton collisions in the final state containing a lepton and at least four jets. Using a dataset corresponding to an integrated luminosity of 5.4 fb-1, collected by the D0 experiment at the Fermilab Tevatron Collider, we measure the t{bar t} forward-backward asymmetry to be (9.2 ± 3.7)% at the reconstruction level. When corrected for detector acceptance and resolution, the asymmetry is found to be (19.6 ± 6.5)%. We also measure a corrected asymmetry based on the lepton from a top quark decay, found to be (15.2 ± 4.0)%.more »The results are compared to predictions based on the next-to-leading-order QCD generator mc@nlo. The sensitivity of the measured and predicted asymmetries to the modeling of gluon radiation is discussed.« less
Challenges to quantum chromodynamics: Anomalous spin, heavy quark, and nuclear phenomena
Brodsky, S.J.
1989-11-01
The general structure of QCD meshes remarkably well with the facts of the hadronic world, especially quark-based spectroscopy, current algebra, the approximate point-like structure of large momentum transfer inclusive reactions, and the logarithmic violation of scale invariance in deep inelastic lepton-hadron reactions. QCD has been successful in predicting the features of electron-positron and photon-photon annihilation into hadrons, including the magnitude and scaling of the cross sections, the shape of the photon structure function, the production of hadronic jets with patterns conforming to elementary quark and gluon subprocesses. The experimental measurements appear to be consistent with basic postulates of QCD, that the charge and weak currents within hadrons are carried by fractionally-charged quarks, and that the strength of the interactions between the quarks, and gluons becomes weak at short distances, consistent with asymptotic freedom. Nevertheless in some cases, the predictions of QCD appear to be in dramatic conflict with experiment. The anomalies suggest that the proton itself as a much more complex object than suggested by simple non-relativistic quark models. Recent analyses of the proton distribution amplitude using QCD sum rules points to highly-nontrival proton structure. Solutions to QCD in one-space and one-time dimension suggest that the momentum distributions of non-valence quarks in the hadrons have a non-trival oscillatory structure. The data seems also to be suggesting that the intrinsic'' bound state structure of the proton has a non- negligible strange and charm quark content, in addition to the extrinsic'' sources of heavy quarks created in the collision itself. 144 refs., 46 figs., 2 tabs.
Top-quark transverse-momentum distributions in t-channel single-top production
Nikolaos Kidonakis
2013-06-15
I present approximate next-to-next-to-leading-order (NNLO) top-quark transverse momentum, pT, distributions in t-channel single-top production. These distributions are derived from next-to-next-to-leading-logarithm (NNLL) soft-gluon resummation. Theoretical results for the single top as well as the single antitop pT distributions are shown for LHC and Tevatron energies.
Yvonne Peters; for the Atlas Collaboration; CDF Collaboration; CMS Collaboration; D0 Collaboration
2011-12-02
Since its discovery in 1995 by the CDF and D0 collaborations at the Fermilab Tevatron collider, the top quark has undergone intensive studies. Besides the Tevatron experiments, with the start of the LHC in 2010 a top quark factory started its operation. It is now possible to measure top quark properties simultaneously at four different experiments, namely ATLAS and CMS at LHC and CDF and D0 at Tevatron. Having collected thousands of top quarks each, several top quark properties have been measured precisely, while others are being measured for the first time. In this article, recent measurements of top quark properties from ATLAS, CDF, CMS and D0 are presented, using up to 5.4 fb-1 of integrated luminosity at the Tevatron and 1.1 fb^-1 at the LHC. In particular, measurements of the top quark mass, mass difference, forward backward charge asymmetry, tt - spin correlations, the ratio of branching fractions, W helicity, anomalous couplings, color flow and the search for flavor changing neutral currents are discussed.
Efe Yazgan; for the CMS Collaboration
2014-09-12
Measurements involving top quarks provide important tests of QCD. A selected set of top quark measurements in CMS including the strong coupling constant, top quark pole mass, constraints on parton distribution functions, top quark pair differential cross sections, ttbar+0 and >0 jet events, top quark mass studied using various kinematic variables in different phase-space regions, and alternative top quark mass measurements is presented. The evolution of expected uncertainties in future LHC runs for the standard and alternative top quark mass measurements is also presented.
Phenomenological analysis of Higgs boson production through gluon fusion in association with jets
Nicolas Greiner; Stefan Hoeche; Gionata Luisoni; Marek Schonherr; Jan-Christopher Winter; Valery Yundin
2015-06-02
We present a detailed phenomenological analysis of the production of a Standard Model Higgs boson in association with up to three jets. We consider the gluon fusion channel using an effective theory in the large top-quark mass limit. Higgs boson production in gluon fusion constitutes an irreducible background to the vector boson fusion (VBF) process; hence the precise knowledge of its characteristics is a prerequisite for any measurement in the VBF channel. The calculation is carried out at next-to-leading order (NLO) in QCD in a fully automated way by combining the two programs GoSam and Sherpa. We present numerical results for a large variety of observables for both standard cuts and VBF selection cuts. We find that for all jet multiplicities the NLO corrections are sizeable. This is particularly true in the presence of kinematic selections enhancing the VBF topology, which are based on vetoing additional jet activity. In this case, precise predictions for the background can be made using our calculation by taking the difference between the inclusive H+2 jets and the inclusive H+3 jets result.
Higgs Production by Gluon initiated Weak Boson Fusion
M. M. Weber
2007-09-17
The gluon-gluon induced terms for Higgs production through weak-boson fusion are calculated. They form a finite and gauge-invariant subset of the NNLO corrections in the strong coupling constant. This is also the lowest order with sizeable t-channel colour exchange contributions, leading to additional hadronic activity between the outgoing jets.
Tony M. Liss
2012-12-03
I review the latest results on properties of the top quark from the Tevatron and the LHC, including results measured in $t\\bar{t}$ and single-top events on the mass, width, couplings, and spin correlations.
Suzuki, M.
2010-01-01
i'iAsm Heavy Quark Jets iBirijets. Short-distance vs long-than a few wide angle sub-jets at to draw first skelton jet
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Qi Liu; Norman H. Christ; Chulwoo Jung
2012-06-01
We present a systematic study of the effectiveness of light quark mass reweighting. This method allows a single lattice QCD ensemble, generated with a specific value of the dynamical light quark mass, to be used to determine results for other, nearby light dynamical quark masses. We study two gauge field ensembles generated with 2+1 flavors of dynamical domain wall fermions with light quark masses m_l=0.02 (m_\\pi=620 MeV) and m_l=0.01 (m_\\pi=420 MeV). We reweight each ensemble to determine results which could be computed directly from the other and check the consistency of the reweighted results with the direct results. The large difference between the 0.02 and 0.01 light quark masses suggests that this is an aggressive application of reweighting as can be seen from fluctuations in the magnitude of the reweighting factor by four orders of magnitude. Never-the-less, a comparison of the reweighed topological charge, average plaquette, residual mass, pion mass, pion decay constant, and scalar correlator between these two ensembles shows agreement well described by the statistical errors. The issues of the effective number of configurations and finite sample size bias are discussed. An examination of the topological charge distribution implies that it is more favorable to reweight from heavier mass to lighter quark mass.
Continuum Study of Heavy Quark Diffusion
Thomas Neuhaus
2015-04-28
We report on a lattice investigation of heavy quark momentum diffusion within the pure SU(3) plasma above the deconfinement transition with the quarks treated to leading order in the heavy mass expansion. We measure the relevant "colour-electric" Euclidean correlator and based on several lattice spacing's perform the continuum extrapolation. This is necessary not only to remove cut-off effects but also the analytic continuation for the extraction of transport coefficients is well-defined only when a continuous function of the Euclidean time variable is available. We pay specific attention to scale setting in SU(3). In particular we present our determination for the critical temperature $T_c=1/({N_\\tau}a) $ at values of $N_\\tau \\le 22$.
Physics with boosted top quarks
Elin Bergeaas Kuutmann
2014-08-29
The production at the LHC of boosted top quarks (top quarks with a transverse momentum that greatly exceeds their rest mass) is a promising process to search for phenomena beyond the Standard Model. In this contribution several examples are discussed of new techniques to reconstruct and identify (tag) the collimated decay topology of the boosted hadronic decays of top quarks. Boosted top reconstruction techniques have been utilized in searches for new physical phenomena. An overview is given of searches by ATLAS, CDF and CMS for heavy new particles decaying into a top and an anti-top quark, vector-like quarks and supersymmetric partners to the top quark.
The study of quark-gluon matter in high-energy nucleus-nucleus collisions
A. Andronic
2012-10-30
A short overview is given on the study of hot matter produced in relativistic nucleus-nucleus collisions, with emphasis on recent measurements at the LHC.
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Quark helicity flip and the transverse spin dependence of inclusive DIS
Andrei Afanasev; Mark Strikman; Christian Weiss
2007-05-21
Inclusive DIS with unpolarized beam exhibits a subtle dependence on the transverse target spin, arising from the interference of one-photon and two-photon exchange amplitudes in the cross section. We argue that this observable probes mainly the quark helicity-flip amplitudes induced by the non-perturbative vacuum structure of QCD (spontaneous chiral symmetry breaking). This conjecture is based on (a) the absence of significant Sudakov suppression of the helicity-flip process if soft gluon emission in the quark subprocess is limited by the chiral symmetry breaking scale mu^2_{chiral} >> Lambda^2_{QCD}; (b) the expectation that the quark helicity-conserving twist-3 contribution is small. The normal target spin asymmetry is estimated to be of the order 10^{-4} in the kinematics of the planned Jefferson Lab Hall A experiment.
Lorentz and CPT Violation in Top-Quark Production and Decay
Berger, Micheal S; Liu, Zhi
2015-01-01
The prospects are explored for testing Lorentz and CPT symmetry in the top-quark sector. We present the relevant Lagrange density, discuss physical observables, and describe the signals to be sought in experiments. For top-antitop pair production via quark or gluon fusion with subsequent semileptonic or hadronic decays, we obtain the matrix element in the presence of Lorentz violation using the narrow-width approximation. The issue of testing CPT symmetry in the top-quark sector is also addressed. We demonstrate that single-top production and decay is well suited to a search for CPT violation, and we present the matrix elements for single-top production in each of the four tree-level channels. Our results are applicable to searches for Lorentz violation and studies of CPT symmetry in collider experiments, including notably high-statistics top-antitop and single-top production at the Large Hadron Collider.
Evolution of gluon TMD at low and moderate x
I. Balitsky; A. Tarasov
2014-11-05
We study how the rapidity evolution of gluon transverse momentum dependent distribution changes from nonlinear evolution at small $x\\ll 1$ to linear double-logarithmic evolution at moderate $x\\sim 1$.
Rapidity evolution of gluon TMD from low to moderate x
I. Balitsky; A. Tarasov
2015-09-29
We study how the rapidity evolution of gluon transverse momentum dependent distribution changes from nonlinear evolution at small $x \\ll 1$ to linear evolution at moderate $x \\sim 1$.
Rapidity evolution of gluon TMD from low to moderate x
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Balitsky, Ian; Tarasov, A.
2015-10-05
In this article, we study how the rapidity evolution of gluon transverse momentum dependent distribution changes from nonlinear evolution at small $x \\ll 1$ to linear evolution at moderate $x \\sim 1$.
Quark Structure of the Nucleon and Angular Asymmetry of Proton-Neutron Hard Elastic Scattering
Carlos G. Granados; Misak M. Sargsian
2009-07-29
We investigate an asymmetry in the angular distribution of hard elastic proton-neutron scattering with respect to 90deg center of mass scattering angle. We demonstrate that the magnitude of the angular asymmetry is related to the helicity-isospin symmetry of the quark wave function of the nucleon. Our estimate of the asymmetry within the quark-interchange model of hard scattering demonstrates that the quark wave function of a nucleon based on the exact SU(6) symmetry predicts an angular asymmetry opposite to that of experimental observations. On the other hand the quark wave function based on the diquark picture of the nucleon produces an asymmetry consistent with the data. Comparison with the data allowed us to extract the relative sign and the magnitude of the vector and scalar diquark components of the quark wave function of the nucleon. These two quantities are essential in constraining QCD models of a nucleon. Overall, our conclusion is that the angular asymmetry of a hard elastic scattering of baryons provides a new venue in probing quark-gluon structure of baryons and should be considered as an important observable in constraining the theoretical models.
Paul B. Mackenzie
1992-12-14
Lattice calculations of heavy quark systems provide very good measures of the lattice spacing, a key element in recent determinations of the strong coupling constant using lattice methods. They also provide excellent testing grounds for lattice methods in general. I review recent phenomenological and technical developments in this field.
Axions and saxions from the primordial supersymmetric plasma and extra radiation signatures
Graf, Peter; Steffen, Frank Daniel, E-mail: graf@mpp.mpg.de, E-mail: steffen@mpp.mpg.de [Max-Planck-Institut für Physik, Föhringer Ring 6, D–80805 Munich (Germany)
2013-02-01
We calculate the rate for thermal production of axions and saxions via scattering of quarks, gluons, squarks, and gluinos in the primordial supersymmetric plasma. Systematic field theoretical methods such as hard thermal loop resummation are applied to obtain a finite result in a gauge-invariant way that is consistent to leading order in the strong gauge coupling. We calculate the thermally produced yield and the decoupling temperature for both axions and saxions. For the generic case in which saxion decays into axions are possible, the emitted axions can constitute extra radiation already prior to big bang nucleosynthesis and well thereafter. We update associated limits imposed by recent studies of the primordial helium-4 abundance and by precision cosmology of the cosmic microwave background and large scale structure. We show that the trend towards extra radiation seen in those studies can be explained by late decays of thermal saxions into axions and that upcoming Planck results will probe supersymmetric axion models with unprecedented sensitivity.
Top quark pair production and top quark properties at CDF
Chang-Seong Moon
2014-11-01
We present the most recent measurements of top quark pairs production and top quark properties in proton-antiproton collisions with center-of-mass energy of 1.96 TeV using CDF II detector at the Tevatron. The combination of top pair production cross section measurements and the direct measurement of top quark width are reported. The test of Standard Model predictions for top quark decaying into $b$-quarks, performed by measuring the ratio $R$ between the top quark branching fraction to $b$-quark and the branching fraction to any type of down quark is shown. The extraction of the CKM matrix element $|V_{tb}|$ from the ratio $R$ is discussed. We also present the latest measurements on the forward-backward asymmetry ($A_{FB}$) in top anti-top quark production. With the full CDF Run II data set, the measurements are performed in top anti-top decaying to final states that contain one or two charged leptons (electrons or muons). In addition, we combine the results of the leptonic forward-backward asymmetry in $t\\bar t$ system between the two final states. All the results show deviations from the next-to-leading order (NLO) standard model (SM) calculation.
Karolos Potamianos
2011-12-01
We present the recent results of top-quark physics using up to 6 fb$^{-1}$ of $p\\bar{p}$ collisions analyzed by the CDF collaboration. The large number of top quark events analyzed, of the order of several thousands, allows stringent checks of the standard model predictions. Also, the top quark is widely believed to be a window to new physics. We present the latest measurements of top quark intrinsic properties as well as direct searches for new physics in the top sector.
Simulations with dynamical HISQ quarks
A. Bazavov; C. Bernard; C. DeTar; W. Freeman; Steven Gottlieb; U. M. Heller; J. E. Hetrick; J. Laiho; L. Levkova; M. Oktay; J. Osborn; R. L. Sugar; D. Toussaint; R. S. Van de Water
2010-12-06
We report on the status of a program of generating and using configurations with four flavors of dynamical quarks, using the HISQ action. We study the lattice spacing dependence of physical quantities in these simulations, using runs at several lattice spacings, but with the light quark mass held fixed at two tenths of the strange quark mass. We find that the lattice artifacts in the HISQ simulations are much smaller than those in the asqtad simulations at the same lattice spacings and quark masses. We also discuss methods for setting the scale, or assigning a lattice spacing to ensembles run at unphysical parameters.
Cold quark matter in compact stars
Franzon, B.; Fogaca, D. A.; Navarra, F. S.; Horvath, J. E.
2013-03-25
We used an equation of state for the cold quark matter to the study of properties of quark stars. We also discuss the absolute stability of quark matter and compute the mass-radius relation for self-bound stars.
Gluon mass and freezing of the QCD coupling
A. C. Aguilar; J. Papavassiliou
2007-11-06
Infrared finite solutions for the gluon propagator of pure QCD are obtained from the gauge-invariant non-linear Schwinger-Dyson equation formulated in the Feynman gauge of the background field method. These solutions may be fitted using a massive propagator, with the special characteristic that the effective mass employed drops asymptotically as the inverse square of the momentum transfer, in agreement with general operator-product expansion arguments. Due to the presence of the dynamical gluon mass the strong effective charge extracted from these solutions freezes at a finite value, giving rise to an infrared fixed point for QCD.
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L. Cerrito
2004-07-16
Preliminary results on the measurement of the top quark mass at the Tevatron Collider are presented. In the dilepton decay channel, the CDF Collaboration measures m{sub t} = 175.0{sub -16.9}{sup +17.4}(stat.){+-}8.4(syst.) GeV/c{sup 2}, using a sample of {approx} 126 pb{sup -1} of proton-antiproton collision data at {radical}s = 1.96 TeV (Run II). In the lepton plus jets channel, the CDF Collaboration measures 177.5{sub -9.4}{sup +12.7}(stat.) {+-} 7.1(syst.) GeV/c{sup 2}, using a sample of {approx} 102 pb{sup -1} at {radical}s = 1.96 TeV. The D0 Collaboration has newly applied a likelihood technique to improve the analysis of {approx} 125 pb{sup -1} of proton-antiproton collisions at {radical}s = 1.8 TeV (Run I), with the result: m{sub t} = 180.1 {+-} 3.6(stat.) {+-}3.9(syst.) GeV/c{sup 2}. The latter is combined with all the measurements based on the data collected in Run I to yield the most recent and comprehensive experimental determination of the top quark mass: m{sub t} = 178.0 {+-} 2.7(stat.) {+-} 3.3(syst.) GeV/c{sup 2}.
Quantum Collapse in Quark Stars?
Perez Martinez, A.; Perez Rojas, H. [ICIMAF, Calle E esq 15 No. 309 Vedado (Cuba); Mosquera Cuesta, H. J. [Centro Brasileiro de Pesquisas Fisicas, Laboratorio de Cosmologia e Fisica Experimental de Altas Energias, Rua Dr. Xavier Sigaud 150, Urca, CEP 22290-180, Rio de Janeiro (Brazil)
2006-06-19
Quark matter is expected to exist in the interior of compact stellar objects as neutron stars or even the more exotic strange stars. Bare strange quark stars and (normal) strange quark-matter stars, those possessing a baryon (electron-supported) crust, are hypothesized as good candidates to explain the properties of a set of peculiar stellar sources. In this presentation, we modify the MIT Bag Model by including the electromagnetic interaction. We also show that this version of the MIT model implies the anisotropy of the Bag pressure due to the presence of the magnetic field. The equations of state of degenerate quarks gases are studied in the presence of ultra strong magnetic fields. The behavior of a system made-up of quarks having (or not) anomalous magnetic moment is reviewed. A structural instability is found, which is related to the anisotropic nature of the pressures in this highly magnetized matter.
Top-quark production measurements
Markus Cristinziani
2015-11-13
Recent measurements of top-quark production at hadron colliders are reviewed. The inclusive top-quark pair production is determined at four centre-of-mass energies at Tevatron and LHC with experimental uncertainties that are close to the uncertainties in theoretical calculations at next-to-next-to-leading order in QCD. Several differential measurements are performed and compared to simulation. Production of single top quarks is studied in the three different production channels. Top-quark pair production with neutral and charged vector bosons has been observed by the LHC experiments. Finally, production of additional heavy flavour quark pairs ($b\\bar{b}$, $t\\bar{t}$) is studied or searched for.
Quarks with Integer Electric Charge
J. LaChapelle
2015-01-26
Within the context of the Standard Model, quarks are placed in a $(\\mathbf{3},\\mathbf{2})\\oplus (\\mathbf{3},\\bar{\\mathbf{2}})$ matter field representation of $U_{EW}(2)$. Although the quarks carry unit intrinsic electric charge in this construction, anomaly cancellation constrains the Lagrangian in such a way that the quarks' associated currents couple to the photon with the usual 2/3 and 1/3 fractional electric charge associated with conventional quarks. The resulting model is identical to the Standard Model in the $SU_C(3)$ sector: However, in the $U_{EW}(2)$ sector it is similar but not necessarily equivalent. Off hand, the model appears to be phenomenologically equivalent to the conventional quark model in the electroweak sector for experimental conditions that preclude observation of individual constituent currents. On the other hand, it is conceivable that detailed analyses for electroweak reactions may reveal discrepancies with the Standard Model in high energy and/or large momentum transfer reactions. The possibility of quarks with integer electric charge strongly suggests the notion that leptons and quarks are merely different manifestations of the same underlying field. A speculative model is proposed in which a phase transition is assumed to occur between $SU_C(3)\\otimes U_{EM}(1)$ and $U_{EM}(1)$ regimes. This immediately; explains the equality of lepton/quark generations and lepton/hadron electric charge, relates neutrino oscillations to quark flavor mixing, reduces the free parameters of the Standard Model, and renders the issue of quark confinement moot.
Leading soft gluon production in high energy nuclear collisions
Xiaofeng Guo
1999-02-23
The leading soft gluon p_T distribution in heavy ion collisions was obtained by Kovner, McLerran, and Weigert after solving classical Yang-Mills equations. I show explicitly this result can be understood in terms of conventional QCD perturbation theory. I also demonstrate that the key logarithm in their result represents the logarithm in DGLAP evolution equations.
Non-linear BFKL dynamics: color screening vs. gluon fusion
R. Fiore; P. V. Sasorov; V. R. Zoller
2012-11-01
A feasible mechanism of unitarization of amplitudes of deep inelastic scattering at small values of Bjorken $x$ is the gluon fusion. However, its efficiency depends crucially on the vacuum color screening effect which accompanies the multiplication and the diffusion of BFKL gluons from small to large distances. From the fits to lattice data on field strength correlators the propagation length of perturbative gluons is $R_c\\simeq 0.2-0.3$ fermi. The probability to find a perturbative gluon with short propagation length at large distances is suppressed exponentially. It changes the pattern of (dif)fusion dramatically. The magnitude of the fusion effect appears to be controlled by the new dimensionless parameter $\\sim R_c^2/8B$, with the diffraction cone slope $B$ standing for the characteristic size of the interaction region. It should slowly $\\propto 1/\\ln Q^2$ decrease at large $Q^2$. Smallness of the ratio $R_c^2/8B$ makes the non-linear effects rather weak even at lowest Bjorken $x$ available at HERA. We report the results of our studies of the non-linear BFKL equation which has been generalized to incorporate the running coupling and the screening radius $R_c$ as the infrared regulator.
Color Glass Condensate and Glasma
F. Gelis
2012-11-26
We review the Color Glass Condensate effective theory, that describes the gluon content of a high energy hadron or nucleus, in the saturation regime. The emphasis is put on applications to high energy heavy ion collisions. After describing initial state factorization, we discuss the Glasma phase, that precedes the formation of an equilibrated quark-gluon plasma. We end this review with a presentation of recent developments in the study of the isotropization and thermalization of the quark-gluon plasma.
Top quark studies at hadron colliders
Sinervo, P.K. [Univ. of Toronto, Ontario (Canada)
1997-01-01
The techniques used to study top quarks at hadron colliders are presented. The analyses that discovered the top quark are described, with emphasis on the techniques used to tag b quark jets in candidate events. The most recent measurements of top quark properties by the CDF and DO Collaborations are reviewed, including the top quark cross section, mass, branching fractions, and production properties. Future top quark studies at hadron colliders are discussed, and predictions for event yields and uncertainties in the measurements of top quark properties are presented.
Higher twists in polarized DIS and the size of the constituent quark
Alexander Sidorov; Christian Weiss
2006-02-15
The spontaneous breaking of chiral symmetry implies the presence of a short-distance scale in the QCD vacuum, which phenomenologically may be associated with the ''size'' of the constituent quark, rho {approx} 0.3 fm. We discuss the role of this scale in the matrix elements of the twist-4 and 3 quark-gluon operators determining the leading power (1/Q{sup 2}-) corrections to the moments of the nucleon spin structure functions. We argue that the flavor-nonsinglet twist-4 matrix element, f{sub 2}{sup u-d}, has a sizable negative value of the order rho{sup -2}, due to the presence of sea quarks with virtualities {approx} rho{sup -2} in the proton wave function. The twist-3 matrix element, d{sub 2}, is not related to the scale rho{sup -2}. Our arguments support the results of previous calculations of the matrix elements in the instanton vacuum model. We show that this qualitative picture is in agreement with the phenomenological higher-twist correction extracted from an NLO QCD fit to the world data on g{sub 1}{sup p} and g{sub 1}{sup n}, which include recent data from the Jefferson Lab Hall A and COMPASS experiments. We comment on the implications of the short-distance scale rho for quark-hadron duality and the x-dependence of higher-twist contributions.
Top Quark Production at the Tevatron Collider
Liang Li
2011-07-21
Top quark physics has been a rich testing ground for the standard model since the top quark discovery in 1995. The large mass of top quark suggests that it could play a special role in searches for new phenomena. In this paper I provide an overview of recent top quark production cross section measurements from both CDF and D0 collaborations and also some new physics searches done in the top quark sector.
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Kong, Kyoungchui; Lee, Hye-Sung; Park, Myeonhun
We suggest top quark decays as a venue to search for light dark force carriers. Top quark is the heaviest particle in the standard model whose decays are relatively poorly measured, allowing sufficient room for exotic decay modes from new physics. A very light (GeV scale) dark gauge boson (Z') is a recently highlighted hypothetical particle that can address some astrophysical anomalies as well as the 3.6 ? deviation in the muon g-2 measurement. We present and study a possible scenario that top quark decays as t ? b W + Z's. This is the same as the dominant topmore »quark decay (t ? b W) accompanied by one or multiple dark force carriers. The Z' can be easily boosted, and it can decay into highly collimated leptons (lepton-jet) with large branching ratio. We discuss the implications for the Large Hadron Collider experiments including the analysis based on the lepton-jets.« less
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Kong, Kyoungchui [Kansas; Lee, Hye-Sung [W&M, JLAB; Park, Myeonhun [Tokyo
2014-04-01
We suggest top quark decays as a venue to search for light dark force carriers. Top quark is the heaviest particle in the standard model whose decays are relatively poorly measured, allowing sufficient room for exotic decay modes from new physics. A very light (GeV scale) dark gauge boson (Z') is a recently highlighted hypothetical particle that can address some astrophysical anomalies as well as the 3.6 ? deviation in the muon g-2 measurement. We present and study a possible scenario that top quark decays as t ? b W + Z's. This is the same as the dominant top quark decay (t ? b W) accompanied by one or multiple dark force carriers. The Z' can be easily boosted, and it can decay into highly collimated leptons (lepton-jet) with large branching ratio. We discuss the implications for the Large Hadron Collider experiments including the analysis based on the lepton-jets.
Gluon polarization measurements with inclusive jets at STAR
Pibero Djawotho; for the STAR Collaboration
2011-06-28
At RHIC kinematics, polarized jet hadroproduction is dominated by $gg$ and $qg$ scattering, making the jet double longitudinal spin asymmetry, $A_{LL}$, sensitive to gluon polarization in the nucleon. I will present STAR results of $A_{LL}$ from inclusive jet measurements for the RHIC 2006 run at center-of-mass energy 200 GeV. I will also discuss the current status of the analysis of data from the 2009 run, also at center-of-mass energy 200 GeV. The results are compared with theoretical calculations of $A_{LL}$ based on various models of the gluon density in the nucleon. The STAR data place significant constraints on allowed theoretical models.
Color structure for soft gluon resummation - a general recipe
Malin Sjodahl
2009-07-31
A strategy for calculating the color structure needed for soft gluon resummation for processes with any number of colored partons is introduced using a N_c --> infinity inspired basis. In this basis a general formalism can be found at the same time as the calculations are simplified. The advantages are illustrated by recalculating the soft anomalous dimension matrix for the processes gg --> gg, q\\qbar --> q \\qbar g and q\\qbar --> ggg.
Search for Electroweak Single-Top Quark Production with the CDF II Experiment
Buehler, Matthias; /Karlsruhe U., EKP
2006-08-01
The CDF II experiment and the Tevatron proton-antiproton collider are parts of the Fermi National Laboratories (Fermilab). The Fermilab is located in the vicinity of Chicago, USA. Today, the Tevatron is the only collider which is able to produce the heaviest known elementary particle, the top quark. The top quark was discovered at the Tevatron by the CDF and the D0 collaborations in 1995 [1]. So far, all the top quarks found are produced via the strong interaction as top-antitop pairs. The Standard Model of elementary particle physics also predicts single-top quark production via the electroweak interaction. This production mode has not yet been observed. The CDF and the D0 collaborations have set upper limits on the cross section for that process in Run I [2, 3] and improved those results in Run II [4, 5]. Single-top quark production is one of the major interests in Run II of the Tevatron as it offers several ways to test the Standard Model and to search for potential physics beyond the Standard Model. The measurement of the cross section of singly produced top quarks via the electroweak interaction offers the possibility to determine the Cabbibo-Kobayashi-Maskawa (CKM) matrix element V{sub tb} directly. The CKM matrix defines the transformation from the eigenstates of the electroweak interactions to the mass eigenstates of the quarks. V{sub tb} gives the strength of the coupling at the Wtb vertex. The single-top quark is produced at this vertex and therefore the cross section of the single-top quark production is directly proportional to |V{sub tb}|{sup 2}. In the Standard Model, three generations of quarks and the unitarity of the CKM matrix are predicted. This leads to V{sub tb} {approx} 1. Up to now, there is no possibility to measure V{sub tb} without using the assumption that there are a certain number of quark generations. Since the measurement of the cross section of single-top quark production is independent of this assumption it could verify another prediction of the Standard Model or give hints towards physics beyond the Standard Model such as a fourth generation of quarks. In addition, electroweak single-top quark production is an important background for the Higgs boson search in the mass range of 90 GeV/c{sup 2} to 130 GeV/c{sup 2} at the Tevatron in the WH channel. Two single-top quark production modes are dominant at the Tevatron, the t-channel or W-gluon fusion and the s-channel or W* process. Since it is challenging to separate the signal from the various background events we use a neural network to combine several variables into one powerful discriminant. The simulated Monte Carlo sample outputs of the neural networks are used as templates for a likelihood fit to the outputs of the neural networks of the data. In this thesis CDF II data corresponding to an integrated luminosity of 695 pb{sup -1} is discussed. As this analysis yields no significant evidence of electroweak single-top production it is not possible to measure any cross sections. Consequently we determine upper limits on the cross sections of the t- and s-channel production separately and combined.
Top-quark production in proton-nucleus and nucleus-nucleus collisions at LHC energies and beyond
David d'Enterria; Krisztian Krajczar; Hannu Paukkunen
2015-04-21
Single and pair top-quark production in proton-lead (p-Pb) and lead-lead (Pb-Pb) collisions at the CERN Large Hadron Collider (LHC) and future circular collider (FCC) energies, are studied with next-to-leading-order perturbative QCD calculations including nuclear parton distribution functions. At the LHC, the pair-production cross sections amount to sigma(t-tbar) = 3.4 mub in Pb-Pb at sqrt(s) = 5.5 TeV, and sigma(t-tbar) = 60 nb in p-Pb at sqrt(s) = 8.8 TeV. At the FCC energies of sqrt(s) = 39 and 63 TeV, the same cross sections are factors of 90 and 55 times larger respectively. In the leptonic final-state t-tbar --> W+b W-bbar --> b bbar l+l- nu+nu-, after typical acceptance and efficiency cuts, one expects about 90 and 300 top-quarks per nominal LHC-year and 4.7 10^4 and 10^5 per FCC-year in Pb-Pb and p-Pb collisions respectively. The total t-tbar cross sections, dominated by gluon fusion processes, are enhanced by 3--8% in nuclear compared to p-p collisions due to an overall net gluon antishadowing, although different regions of their differential distributions are depleted due to shadowing or EMC-effect corrections. The rapidity distributions of the decay leptons in t-tbar processes can be used to reduce the uncertainty on the Pb gluon density at high virtualities by up to 30% at the LHC (full heavy-ion programme), and by 70% per FCC-year. The cross sections for single-top production in electroweak processes are also computed, yielding about a factor of 30 smaller number of measurable top-quarks after cuts, per system and per year.
Saskia Mioduszewski
2010-09-01
"Probing the Matter Created at RHIC." Mioduszewski discusses the results from RHIC's experimental collaborations and how researchers hope to create a form of matter in which the basic building blocks of matter -- quarks and gluons -- interact freely in what is called quark gluon plasma.
Quarks and Antiquarks in Nuclei
Jason R. Smith
2005-08-19
The Chiral Quark-Soliton model provides the quark and antiquark substructure of the nucleon, which is embedded in nuclear matter. This provides a new way to asses the effects of the nuclear medium on the nucleon. We calculate nuclear binding and saturation, describe the European Muon Collaboration (EMC) effect consistently with Drell-Yan experiments, and predict modifications to the polarized parton distributions. We also calculate the electromagnetic form factors of a bound proton, and find significant modifications of the electromagnetic form factors in the nuclear environment. In every case, the properties of the sea of quark-antiquark pairs in the nucleon are very important, and serve to mitigate the valence quark effect. The changes in the sea quarks when the nucleon is immersed in the nuclear medium are the primary mode by which consistency is maintained with experimental constraints (Drell-Yan data, magnetic moment), while still maintaining a significant effect needed to explain the deep inelastic scattering and polarization transfer data.
Hyperfine meson splittings: chiral symmetry versus transverse gluon exchange
Llanes-Estrada, Felipe J; Swanson, Eric S; Szczepaniak, Adam P; Llanes-Estrada, Felipe J.; Cotanch, Stephen R.; Szczepaniak, Adam P.; Swanson, Eric S.
2004-01-01
Meson spin splittings are examined within an effective Coulomb gauge QCD Hamiltonian incorporating chiral symmetry and a transverse hyperfine interaction necessary for heavy quarks. For light and heavy quarkonium systems the pseudoscalar-vector meson spectrum is generated by approximate BCS-RPA diagonalizations. This relativistic formulation includes both $S$ and $D$ waves for the vector mesons which generates a set of coupled integral equations. A smooth transition from the heavy to the light quark regime is found with chiral symmetry dominating the $\\pi$-$\\rho$ mass difference. A good, consistent description of the observed meson spin splittings and chiral quantities, such as the quark condensate and the $\\pi$ mass, is obtained. Similar comparisons with TDA diagonalizations, which violate chiral symmetry, are deficient for light pseudoscalar mesons indicating the need to simultaneously include both chiral symmetry and a hyperfine interaction. The $\\eta_b$ mass is predicted to be around 9400 MeV consistent w...
Quark masses: An environmental impact statement
Kimchi, Itamar
We investigate worlds that lie on a slice through the parameter space of the standard model over which quark masses vary. We allow as many as three quarks to participate in nuclei, while fixing the mass of the electron and ...
Werner Bernreuther
2008-05-09
The physics perspectives of the production and decay of single top quarks and top quark pairs at the CERN Large Hadron Collider (LHC) are reviewed from a phenomenological point of view.
Nuclear Matter with Relativistic Quark Dynamics
Suisso, E.F.; Batista, E.F.; Araujo, W.R.B. de; Frederico, T.; Carlson, B.V. [Dep. de Fisica, Instituto Tecnologico da Aeronautca, Centro Tecnico Aeroespacial, 12.228-901, Sao Jose dos Campos, Sao Paulo (Brazil)
2004-12-02
We investigate a quark-meson coupling model of the nuclear matter with a light-front nucleon model, where the quarks interact with flavor independent contact force. We found results comparable to the ones obtained with a confining interaction.
Quark stars: their influence on Astroparticle Physics
Sanjay K. Ghosh
2008-08-12
We discuss some of the recent developments in the quark star physics along with the consequences of possible hadron to quark phase transition at high density scenario of neutron stars and their implications on the Astroparticle Physics.
Top Quark Production at the LHC
Francesco Spanò; for the ATLAS; CMS collaborations
2011-12-16
Top quark production in proton proton collisions at the Large Hadron Collider (LHC) is reviewed using data collected by the ATLAS and CMS detectors. Most recent results on searches for new physics related to top quark production mechanism are included.
Schwarz, Thomas A.; /Michigan U.
2006-01-01
Quarks, along with leptons and force carrying particles, are predicted by the Standard Model to be the fundamental constituents of nature. In distinction from the leptons, the quarks interact strongly through the chromodynamic force and are bound together within the hadrons. The familiar proton and neutron are bound states of the light ''up'' and ''down'' quarks. The most massive quark by far, the ''top'' quark, was discovered by the CDF and D0 experiments in March, 1995. The new quark was observed in p{bar p} collisions at 1.8 TeV at the Fermilab Tevatron. The mass of the top quark was measured to be 176 {+-} 13 GeV/c{sup 2} and the cross section 6.8{sub -2.4}{sup +3.6} pb. It is the Q = 2/3, T{sub 3} = +1/2 member of the third generation weak-isospin doublet along with the bottom quark. The top quark is the final Standard Model quark to be discovered. Along with whatever is responsible for electroweak symmetry breaking, top quark physics is considered one of the least understood sectors of the Standard Model and represents a front line of our understanding of particle physics. Currently, the only direct measurements of top quark properties come from the CDF and D0 experiments observing p{bar p} collisions at the Tevatron. Top quark production at the Tevatron is almost exclusively by quark-antiquark annihilation, q{bar q} {yields} t{bar t} (85%), and gluon fusion, gg {yields} t{bar t} (15%), mediated by the strong force. The theoretical cross-section for this process is {sigma}{sub t{bar t}} = 6.7 {+-} 0.8 pb for m{sub t} = 175 GeV/c{sup 2}. Top quarks can also be produced at the Tevatron via q{bar b}{prime} {yields} tb and qg {yields} q{prime}tb through the weak interaction. The cross section for these processes is lower (3pb) and the signal is much more difficult to isolate as backgrounds are much higher. The top quark is predicted to decay almost exclusively into a W-boson and a bottom quark (t {yields} Wb). The total decay width t {yields} Wb is {Lambda} = 1.50 GeV. This corresponds to an incredibly short lifetime of 0.5 x 10{sup -24} seconds. This happens so quickly that hadronization and bound states do not take place, which leads to the interesting consequence that the top quark spin information is passed to the decay products.
Top Quark: discovery, present and future Galtieri, The Top Quark, PDG 50th
Galtieri, Lina
1 Top Quark: discovery, present and future Galtieri, The Top Quark, PDG 50th Anniversary. September 23-2006 #12;Chasing the Top Quark 2 Gell-Mann, Zweig uds quarks postulated ('64) GIM mechanism at FNAL 1984 PDG partial listing top should exist Searches at Tristan, PETRA, SPPS, SLC : top not found
Top quark Physics at the Tevatron
Yvonne Peters; for the CDF; D0 Collaborations
2012-01-06
When the heaviest elementary particle known today, the top quark, was discovered in 1995 by the CDF and D0 collaborations at the Fermilab Tevatron collider, a large program to study this particle in details has started. In this article, an overview of the status of top quark physics at the Tevatron is presented. In particular, recent results on top quark production, properties and searches using top quarks are discussed.
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
state. Formed at high temperatures, plasmas consist of freely moving ions and free electrons. They are often called the "fourth state of matter" because their unique physical...
Polarized quark distributions in nuclear matter
Jason R. Smith; Gerald A. Miller
2005-07-22
We compute the polarized quark distribution function of a bound nucleon. The Chiral Quark-Soliton model provides the quark and antiquark substructure of the nucleon embedded in nuclear matter. Nuclear effects cause significant modifications to the polarized distributions including an enhancement of the axial coupling constant.
Non-Perturbative Corrections to Heavy Quark Fragmentation in e^+e^- Annihilation
P. Nason; B. R. Webber
1996-12-13
We estimate the non-perturbative power-suppressed corrections to heavy flavour fragmentation and correlation functions in e^+e^- annihilation, using a model based on the analysis of one-loop Feynman graphs containing a massive gluon. This approach corresponds to the study of infrared renormalons in the large-n_f limit of QCD, or to the assumption of an infrared-finite effective coupling at low scales. We find that the leading corrections to the heavy quark fragmentation function are of order $\\lambda/M$, where $\\lambda$ is a typical hadronic scale ($\\lambda\\sim 0.4$ GeV) and M is the heavy quark mass. The inclusion of higher corrections corresponds to convolution with a universal function of M(1-x) concentrated at values of its argument of order $\\lambda$, in agreement with intuitive expectations. On the other hand, corrections to heavy quark correlations are very small, of the order of $(\\lambda/Q)^p$, where Q is the centre-of-mass energy and $p \\ge 2$.
Top-Quark Physics Results From LHC
Luca Fiorini
2012-01-30
The top-quark is a fundamental element of the physics program at the Large Hadron Collider (LHC). We review the current status of the top-quark measurements performed by ATLAS and CMS experiments in pp collisions at sqrt(s)=7 TeV by presenting the recent results of the top-quark production rates, top mass measurements and additional top quark properties. We will also describe the recent searches for physics beyond the Standard Model in the top-quark sector.
Top Quark Physics at the Tevatron
Frederic Deliot; Douglas Glenzinski
2011-10-10
We review the field of top-quark physics with an emphasis on experimental techniques. The role of the top quark in the Standard Model of particle physics is summarized and the basic phenomenology of top-quark production and decay is introduced. We discuss how contributions from physics beyond the Standard Model could affect top-quark properties or event samples. The many measurements made at the Fermilab Tevatron, which test the Standard Model predictions or probe for direct evidence of new physics using the top-quark event samples, are reviewed here.
R. Y. Peters
2014-08-10
Years after its discovery in 1995 by CDF and D0, the top quark still undergoes intense investigations at the Tevatron. Using up to the full Run~II data sample, new measurements of top quark production and properties by the D0 Collaboration are presented. In particular, the first observation of single top quark s-channel production, the measurement of differential ttbar distributions, forward-backward ttbar asymmetry, a new measurement of the top quark mass, and a measurement of the top quark charge are discussed.
Hershcovitch, Ady (Mount Sinai, NY); Sharma, Sushil (Hinsdale, IL); Noonan, John (Naperville, IL); Rotela, Elbio (Clarendon Hills, IL); Khounsary, Ali (Hinsdale, IL)
2003-01-01
A plasma valve includes a confinement channel and primary anode and cathode disposed therein. An ignition cathode is disposed adjacent the primary cathode. Power supplies are joined to the cathodes and anode for rapidly igniting and maintaining a plasma in the channel for preventing leakage of atmospheric pressure through the channel.
Three lectures on the physics of small x and high gluon density
McLerran, Larry [Theoretical Physics Institute, University of Minnesota, Minneapolis, Minnesota 55455 (United States)
1999-10-25
In these lectures, I shall discuss small x physics and the consequences of the high gluon density which arises as x decreases. I argue that an understanding of this problem would lead to knowledge of the high energy asymptotics of hadronic processes. The high gluon density should allow a first principles computation of these asymptotics from QCD.
Experimental studies of unbiased gluon jets from e^+e^? annihilations using the jet boost algorithm
Wilson, Graham Wallace; Abbiendi, G.; Ainsley, C.; Å kesson, P. F.; Alexander, G.; Allison, J.; Amaral, P.; Anagnostou, G.; Anderson, K.J.; Arcelli, S.; Asai, S.; Axen, D.; Azuelos, G.; Bailey, I.; Barberio, E.
2004-02-25
We present the first experimental results based on the jet boost algorithm, a technique to select unbiased samples of gluon jets in e^+e^? annihilations, i.e. gluon jets free of biases introduced by event selection or jet finding criteria. Our...
Gluon distribution functions and Higgs boson production at moderate transverse momentum
Sun P.; Yuan F.; Xiao, B.W.
2011-11-04
We investigate the gluon distribution functions and their contributions to the Higgs boson production in pp collisions in the transverse momentum-dependent factorization formalism. In addition to the usual azimuthal symmetric transverse momentum-dependent gluon distribution, we find that the azimuthal correlated gluon distribution also contributes to the Higgs boson production. This explains recent findings on the additional contribution in the transverse momentum resummation for the Higgs boson production as compared to that for electroweak boson production processes. We further examine the small-x naive kt-factorization in the dilute region and find that the azimuthal correlated gluon distribution contribution is consistently taken into account. The result agrees with the transverse momentum-dependent factorization formalism. We comment on the possible breakdown of the naive kt-factorization in the dense medium region, due to the unique behaviors for the gluon distributions.
LPM Interference and Cherenkov-like Gluon Bremsstrahlung in DenseMatter
Majumder, Abhijit; Wang, Xin-Nian
2005-07-26
Gluon bremsstrahlung induced by multiple parton scattering in a finite dense medium has a unique angular distribution with respect to the initial parton direction. A dead-cone structure with an opening angle; theta2{sub 0}; approx 2(1-z)/(zLE) for gluons with fractional energy z arises from the Landau-Pomeran chuck-Migdal (LPM) interference. In a medium where the gluon's dielectric constant is; epsilon>1, the LPM interference pattern is shown to become Cherenkov-like with an increased opening angle determined by the dielectric constant$/cos2/theta{sub c}=z+(1-z)//epsilon$. For a large dielectric constant/epsilon; gg 1+2/z2LE, the corresponding total radiative parton energy loss is about twice that from normal gluon bremsstrahlung. Implications of this Cherenkov-like gluon bremsstrahlung to the jet correlation pattern in high-energy heavy-ion collisions is discussed.
The transport coefficient $\\hat{q}$ in an anisotropic plasma
Yacine Mehtar-Tani
2009-09-15
We investigate the jet quenching parameter in the case of a fast moving quark in an anisotropic plasma. In the leading log approximation, strong indications are found that the transport coefficient increases with increasing anisotropy. Implications for the phenomenology at RHIC are discussed.
Top-quark production in proton-nucleus and nucleus-nucleus collisions at LHC energies and beyond
d'Enterria, David; Paukkunen, Hannu
2015-01-01
Single and pair top-quark production in proton-lead (p-Pb) and lead-lead (Pb-Pb) collisions at the CERN Large Hadron Collider (LHC) and future circular collider (FCC) energies, are studied with next-to-leading-order perturbative QCD calculations including nuclear parton distribution functions. At the LHC, the pair-production cross sections amount to sigma(t-tbar) = 3.4 mub in Pb-Pb at sqrt(s) = 5.5 TeV, and sigma(t-tbar) = 60 nb in p-Pb at sqrt(s) = 8.8 TeV. At the FCC energies of sqrt(s) = 39 and 63 TeV, the same cross sections are factors of 90 and 55 times larger respectively. In the leptonic final-state t-tbar --> W+b W-bbar --> b bbar l+l- nu+nu-, after typical acceptance and efficiency cuts, one expects about 90 and 300 top-quarks per nominal LHC-year and 4.7 10^4 and 10^5 per FCC-year in Pb-Pb and p-Pb collisions respectively. The total t-tbar cross sections, dominated by gluon fusion processes, are enhanced by 3--8% in nuclear compared to p-p collisions due to an overall net gluon antishadowing, altho...
Top quark physics in hadron collisions
Wolfgang Wagner
2007-08-03
The top quark is the heaviest elementary particle observed to date. Its large mass makes the top quark an ideal laboratory to test predictions of perturbation theory concerning heavy quark production at hadron colliders. The top quark is also a powerful probe for new phenomena beyond the Standard Model of particle physics. In addition, the top quark mass is a crucial parameter for scrutinizing the Standard Model in electroweak precision tests and for predicting the mass of the yet unobserved Higgs boson. Ten years after the discovery of the top quark at the Fermilab Tevatron top quark physics has entered an era where detailed measurements of top quark properties are undertaken. In this review article an introduction to the phenomenology of top quark production in hadron collisions is given, the lessons learned in Tevatron Run I are summarized, and first Run II results are discussed. A brief outlook to the possibilities of top quark research a the Large Hadron Collider, currently under construction at CERN, is included.
Longitudinal Gluon Polarization in RHIC Double-Spin Asymmetries
B. Jager; S. Kretzer; M. Stratmann; W. Vogelsang
2004-08-25
The longitudinally polarized gluon density is probed sensitively in hard collisions of polarized protons under the condition that the dominant dynamics are perturbative and of leading twist origin. First data have recently been presented by Phenix on the double-spin asymmetry A_{LL}^{pi} for pi^0 production at moderate transverse momentum p_\\perp \\simeq 1 - 4 GeV and central rapidity. By means of a systematic investigation of the relevant degrees of freedom we show that the perturbative QCD framework at leading power in p_\\perp produces an asymmetry that is basically positive definite in this kinematic range, i.e. A_{LL}^{pi}\\gtrsim O(-10^{-3}) .
Light quark masses using domain wall fermions
Tom Blum; Amarjit Soni; Matthew Wingate
1998-09-10
We compute the one-loop self-energy correction to the massive domain wall quark propagator. Combining this calculation with simulations at several gauge couplings, we estimate the strange quark mass in the continuum limit. The perturbative one-loop mass renormalization is comparable to that for Wilson quarks and considerably smaller than that for Kogut-Susskind quarks. Also, scaling violations appear mild in comparison to other errors at present. Given their good chiral behavior and these features, domain wall quarks are attractive for evaluating the light quark masses. Our preliminary quenched result is m_s(2 GeV) = 82(15) MeV in the ${\\bar{MS}}$ scheme.
Detecting Fourth Generation Quarks at Hadron Colliders
David Atwood; Sudhir Kumar Gupta; Amarjit Soni
2011-07-13
We consider the phenomenology of the fourth generation heavy quarks which would be pair produced at the LHC. We show that if such a quark with a mass in the phenomenologically interesting range of 400 GeV--600 GeV decays to a light quark and a W-boson, it will produce a signal in a number of channels which can be seen above the background from the three generation Standard Model processes. In particular, such quarks could be seen in channels where multiple jets are present with large missing momentum and either a single hard lepton, an opposite sign hard lepton pair or a same sign lepton pair. In the same sign dilepton channel there is little background and so an excess of such pairs at large invariant mass will indicate the presence of heavy down type quarks. More generally, in our study, the main tool we use to determine the mass of the heavy quark in each of the channels we consider is to use the kinematics of the decay of such quarks to resolve the momenta of the unobserved neutrinos. We show how this can be carried out, even in cases where the kinematics is under-determined by use of the approximation, which holds quite well, that the two heavy quarks are nearly at rest in the center of mass frame. Since it is very likely that at least the lightest heavy quark decays in the mode we consider, this means that it should be observed at the LHC. Indeed, it is expected that the mass splitting between the quarks is less than $m_W$ so that if the Cabbibo-Kobayshi-Maskawa (CKM) matrix element between the fourth and lower generations are not too small, both members of the fourth generation quark doublet will decay in this way. If this is so, the combined signal of these two quarks will make the signal for the fourth generation somewhat more prominent.
Top quark properties at the Tevatron
Andreas Werner Jung
2014-12-12
Recent measurements of top-quark properties at the Tevatron, including top quark production asymmetries and properties, are presented. Latest updates of measurements of top quark production asymmetries include the measurement of the $t\\bar{t}$ production asymmetry by D0 employing the full Run II data set, in the lepton + jets and dilepton decay channel. Within their uncertainties the results from all these measurements agree with their respective Standard Model expectation.
Gravity Dual Corrections to the Heavy Quark Potential at Finite-Temperature
Hovhannes R. Grigoryan; Yuri V. Kovchegov
2011-06-23
We apply gauge/gravity duality to compute $1/N^2_c$ corrections to the heavy quark potentials of a quark--anti-quark pair ($Q\\bar Q$) and of a quark--quark pair ($QQ$) immersed into the strongly coupled N = 4 SYM plasma. On the gravity side these corrections come from the exchanges of supergravity modes between two string worldsheets stretching from the UV boundary of AdS space to the black hole horizon in the bulk and smeared over $S^5$. We find that the contributions to the $Q\\bar Q$ potential coming from the exchanges of all of the relevant modes (such as dilaton, massive scalar, 2-form field, and graviton) are all attractive, leading to an attractive net $Q\\bar Q$ potential. We show that at large separations $r$ and/or high-temperature $T$ the potential is of Yukawa-type, dominated by the graviton exchange, in agreement with earlier findings. On the other hand, at small-$r T$ the $Q\\bar Q$ potential scales as $\\sim (1/r) \\ln (1/rT)$. In the case of $QQ$ potential the 2-form contribution changes sign and becomes repulsive: however, the net $QQ$ potential remains attractive. At large-$r T$ it is dominated by the graviton exchange, while at small-$r T$ the $QQ$ potential becomes Coulomb-like.
Zhang, Guang-Peng
2015-01-01
The back-to-back $J/\\psi$ and $\\pi$ associated production at $e^+ e^-$ colliders is proposed to detect the gluon transverse momentum dependent(TMD) fragmentation functions. TMD factorization is assumed for this process. With spinless pion, unpolarized and linearly polarized gluon TMD fragmentation functions can be defined. It is found at parton level the hadronic tensor can be described by four structure functions. As a result, there are three independent angular distributions, of which a $\\cos{2\\phi}$ azimuthal asymmetry is sensitive to the linearly polarized gluon fragmentation function.
Power-like corrections and the determination of the gluon distribution
F. Hautmann
2006-10-06
Power-suppressed corrections to parton evolution may affect the theoretical accuracy of current determinations of parton distributions. We study the role of multigluon-exchange terms in the extraction of the gluon distribution for the Large Hadron Collider (LHC). Working in the high-energy approximation, we analyze multi-gluon contributions in powers of 1/Q^2. We find a moderate, negative correction to the structure function's derivative d F_2 / d \\ln Q^2, characterized by a slow fall-off in the region of low to medium Q^2 relevant for determinations of the gluon at small momentum fractions.
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Aad, G.
2015-07-17
The top quark mass was measured in the channels tt¯? lepton+jets and tt¯? dilepton (lepton = e,?) based on ATLAS data recorded in 2011. The data were taken at the LHC with a proton–proton centre-of-mass energy of ?s = 7 TeV and correspond to an integrated luminosity of 4.6 fb–1. The tt¯? lepton+jets analysis uses a three-dimensional template technique which determines the top quark mass together with a global jet energy scale factor (JSF), and a relative b-to-light-jet energy scale factor (bJSF), where the terms b-jets and light-jets refer to jets originating from b-quarks and u, d, c, s-quarks ormore »gluons, respectively. The analysis of the tt¯? dilepton channel exploits a one-dimensional template method using the m?b observable, defined as the average invariant mass of the two lepton+b-jet pairs in each event. The top quark mass is measured to be 172.33 ± 0.75 (stat + JSF + bJSF) ± 1.02(syst) GeV, and 173.79 ± 0.54(stat) ± 1.30(syst) GeV in the tt¯? lepton+jets and tt¯? dilepton channels, respectively. Thus, the combination of the two results yields mtop = 172.99 ± 0.48(stat) ± 0.78(syst) GeV, with a total uncertainty of 0.91 GeV.« less
J/psi production and elliptic flow in relativistic heavy-ion collisions
Song, Taesoo; Ko, Che Ming; Lee, Su Houng; Xu, Jun.
2011-01-01
Using the two-component model for charmonium production, which includes contributions from both initial hard nucleon-nucleon scattering and from regeneration in the quark-gluon plasma, we study the nuclear modification ...
Inserting Group Variables into Fluid Mechanics
R. Jackiw
2004-10-28
A fluid, like a quark-gluon plasma, may possess degrees of freedom indexed by a group variable, which retains its identity even in the fluid/continuum description. Conventional Eulerian fluid mechanics is extended to encompass this possibility.
Mueller, B.; Springer, R.P.
1994-05-15
This report briefly discusses the following topics: quark-gluon plasma and high-energy collisions; hadron structure and chiral dynamics; nonperturbative studies and nonabelian gauge theories; and studies in quantum field theory.
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
Hard and Thermal Photon Absorption in a Quark- Gluon Plasma E. Palmerduca 1,2 , and R. Fries 2 1 Colgate University, Hamilton, NY 13346 2 Cyclotron Institute, Texas A&M University,...
Partonic coalescence in relativistic heavy ion collisions
Greco, V.; Ko, Che Ming; Levai, P.
2003-01-01
Using a covariant coalescence model, we study hadron production in relativistic heavy ion collisions from both soft partons in the quark-gluon plasma and hard partons in minijets. Including transverse flow of soft partons and independent...
Top 10 Things You Didn't Know About the National Labs | Department...
Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site
for signatures of the form of matter that RHIC was designed to create: the quark-gluon plasma. It is also used to investigate the behavior of matter at high energy densities by...
Jetting into the Moments after the Big Bang | U.S. DOE Office...
Office of Science (SC) Website
shining brightly at temperatures more than 100,000 times hotter than the center of the Sun. To explore the properties of this plasma of quarks and gluons as it expands and cools,...
Top Quark Production Asymmetries AFBt and AFBl
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Berger, Edmond L.; Cao, Qing-Hong; Chen, Chuan-Ren; Yu, Jiang-Hao; Zhang, Hao
2012-02-14
A large forward-backward asymmetry is seen in both the top quark rapidity distribution AFBt and in the rapidity distribution of charged leptons AFBl from top quarks produced at the Tevatron. We study the kinematic and dynamic aspects of the relationship of the two observables arising from the spin correlation between the charged lepton and the top quark with different polarization states. We emphasize the value of both measurements, and we conclude that a new physics model which produces more right-handed than left-handed top quarks is favored by the present data.
Press Pass - Press Release - Single top quark
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
Higgs." Discovering the single top quark production presents challenges similar to the Higgs boson search in the need to extract an extremely small signal from a very large...
Top Quark Physics at the CDF Experiment
Bernd Stelzer; for the CDF Collaboration
2010-07-21
Fermilab's Tevatron accelerator is recently performing at record luminosities that enables a program systematically addressing the physics of top quarks. The CDF collaboration has analyzed up to 5/fb of proton anti-proton collisions from the Tevatron at a center of mass energy of 1.96 TeV. The large datasets available allow to push top quark measurements to higher and higher precision and have lead to the recent observation of electroweak single top quark production at the Tevatron. This article reviews recent results on top quark physics from the CDF experiment.
Top Quark Production Asymmetries AFBt and AFBl
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Berger, Edmond L.; Cao, Qing-Hong; Chen, Chuan-Ren; Yu, Jiang-Hao; Zhang, Hao
2012-02-01
A large forward-backward asymmetry is seen in both the top quark rapidity distribution AFBt and in the rapidity distribution of charged leptons AFBl from top quarks produced at the Tevatron. We study the kinematic and dynamic aspects of the relationship of the two observables arising from the spin correlation between the charged lepton and the top quark with different polarization states. We emphasize the value of both measurements, and we conclude that a new physics model which produces more right-handed than left-handed top quarks is favored by the present data.
Jet substructures of boosted polarized top quarks
Yoshio Kitadono; Hsiang-nan Li
2014-09-05
We study jet substructures of a boosted polarized top quark, which undergoes the semileptonic decay $t\\to b\\ell\
Top quark mass and properties at the Tevatron
J. -F. Arguin; for the CDF; D0 Collaborations
2005-07-29
We present recent analyses of top quark properties performed at Run II of the Tevatron. Measurements of the top quark mass, branching ratios and W boson helicity inside top quark decays are covered.
Quark Masses: An Environmental Impact Statement
Robert L. Jaffe; Alejandro Jenkins; Itamar Kimchi
2009-04-03
We investigate worlds that lie on a slice through the parameter space of the Standard Model over which quark masses vary. We allow as many as three quarks to participate in nuclei, while fixing the mass of the electron and the average mass of the lightest baryon flavor multiplet. We classify as "congenial" worlds that satisfy the environmental constraint that the quark masses allow for stable nuclei with charges one, six, and eight, making organic chemistry possible. Whether a congenial world actually produces observers depends on a multitude of historical contingencies, beginning with primordial nucleosynthesis, which we do not explore. Such constraints may be independently superimposed on our results. Environmental constraints such as the ones we study may be combined with information about the a priori distribution of quark masses over the landscape of possible universes to determine whether the measured values of the quark masses are determined environmentally, but our analysis is independent of such an anthropic approach. We estimate baryon masses as functions of quark masses and nuclear masses as functions of baryon masses. We check for the stability of nuclei against fission, strong particle emission, and weak nucleon emission. For two light quarks with charges 2/3 and -1/3, we find a band of congeniality roughly 29 MeV wide in their mass difference. We also find another, less robust region of congeniality with one light, charge -1/3 quark, and two heavier, approximately degenerate charge -1/3 and 2/3 quarks. No other assignment of light quark charges yields congenial worlds with two baryons participating in nuclei. We identify and discuss the region in quark-mass space where nuclei would be made from three or more baryon species.
A measurement of the top quark's charge
Unalan, Zeynep Gunay; /Michigan State U.
2007-11-01
The top quark was discovered in 1995 at the Fermilab National Accelerator Laboratory (Fermilab). One way to confirm if the observed top quark is really the top quark posited in the Standard Model (SM) is to measure its electric charge. In the Standard Model the top quark is the isospin partner of the bottom quark and is expected to have a charge of +2/3. However, an alternative 'exotic' model has been proposed with a fourth generation exotic quark that has the same characteristics, such as mass, as our observed top but with a charge of -4/3. This thesis presents the first CDF measurement of the top quark's charge via its decay products, a W boson and a bottom quark, using {approx} 1 fb{sup -1} of data. The data were collected by the CDF detector from proton anti-proton (p{bar p}) collisions at {radical}s = 1.96 TeV at Fermilab. We classify events depending on the charges of the bottom quark and associated W boson and count the number of events which appear 'SM-like' or 'exotic-like' with a SM-like event decaying as t {yields} W{sup +}b and an exotic event as t {yields} W{sup -}b. We find the p-value under the Standard Model hypothesis to be 0:35 which is consistent with the Standard Model. We exclude the exotic quark hypothesis at an 81% confidence level, for which we have chosen a priori that the probability of incorrectly rejecting the SM would be 1%. The calculated Bayes Factor (BF) is 2 x Ln(BF)=8.54 which is interpreted as the data strongly favors the Standard Model over the exotic quark hypothesis.
Triangular flow in heavy ion collisions in a multiphase transport model
Xu, Jun; Ko, Che Ming.
2011-01-01
(RHIC) have provided important information on the properties of produced quark-gluon plasma (QGP) [1?4]. In particular, the large elliptic flow observed in experiments has led to the conclusion that the produced quark-gluon plasma is strongly...,10]. With the large parton scattering cross section, the transport model is also able to describe the hexadecupole flow measured at RHIC [11]. More recently, the importance of the triangular flow, which originates from fluctuations in the initial collision...
D-meson enhancement in pp collisions at the LHC due to nonlinear gluon evolution
Dainese, A.; Vogt, R.; Bondila, M.; Eskola, K.J.; Kolhinen, V.J.
2004-08-22
When nonlinear effects on the gluon evolution are included with constraints from HERA, the gluon distribution in the free proton is enhanced at low momentum fractions, x {approx}< 0.01, and low scales, Q{sup 2} {approx}< 10 GeV{sup 2}, relative to standard, DGLAP-evolved, gluon distributions. Consequently, such gluon distributions can enhance charm production in pp collisions at center of mass energy 14 TeV by up to a factor of five at midrapidity, y {approx} 0, and transverse momentum p{sub T} {yields} 0 in the most optimistic case. We show that most of this enhancement survives hadronization into D mesons. Assuming the same enhancement at leading and next-to-leading order, we show that the D enhancement may be measured by D{sup 0} reconstruction in the K{sup -}{pi}{sup +} decay channel with the ALICE detector.
Krzysztof Kutak
2012-11-16
Motivated by forthcoming p-Pb experiments at Large Hadron Collider which require both knowledge of gluon densities accounting for saturation and for processes at a wide range of $p_t$ we study basic momentum space evolution equations of high energy QCD factorization. Solutions of those equations might be used to form a set of gluon densities to calculate observables in generalized high energy factorization. Moreover in order to provide a framework for predictions for exclusive final states in p-Pb scattering with high $p_t$ we rewrite the equation for the high energy factorizable gluon density in a resummed form, similarly to what has been done in \\cite{Kutak:2011fu} for the BK equation. The resummed equation is then extended to account for colour coherence. This introduces an external scale to the evolution of the gluon density, and therefore makes it applicable in studies of final states.
Quarks Pair Up in Protons (and Neutrons) | Jefferson Lab
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
for how the different kinds of quarks behave inside protons and neutrons. In the proton, the down quark contributes surprisingly little to electron-proton interaction. Also,...
Heavy Quarks, QCD, and Effective Field Theory Thomas Mehen 72...
Office of Scientific and Technical Information (OSTI)
Heavy Quarks, QCD, and Effective Field Theory Thomas Mehen 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; 73 NUCLEAR PHYSICS AND RADIATION PHYSICS Heavy Quarks, Quarkonium,...
Quark mass variation constraints from Big Bang nucleosynthesis...
Office of Scientific and Technical Information (OSTI)
Quark mass variation constraints from Big Bang nucleosynthesis Citation Details In-Document Search Title: Quark mass variation constraints from Big Bang nucleosynthesis We study...
Top quark physics expectations at the LHC
Andrei Gaponenko; for the ATLAS Collaboration; for the CMS Collaboration
2008-10-22
The top quark will be produced copiously at the LHC. This will make both detailed physics studies and the use of top quark decays for detector calibration possible. This talk reviews plans and prospects for top physics activities in the ATLAS and CMS experiments.
Heavy quark thermodynamics in full QCD
Konstantin Petrov; RBC-Bielefeld Collaboration
2007-01-22
We analyze the large-distance behaviour of static quark-anti-quark pair correlations in QCD. The singlet free energy is calculated and the entropy contribution to it is identified allowing us to calculate the excess internal energy. The free energy has a sharp drop in the critical region, leading to sharp peaks in both excess entropy and internal energy.
Static quark free energies at finite temperature
Z. Fodor; A. Jakovac; S. D. Katz; K. K. Szabo
2007-10-22
We determine the static quark free energies around the transition temperature using 2+1 flavors of staggered fermions. Simulations are carried out on N_t=4,6,8 and 10 lattices using physical quark masses. The free energies extracted from Polyakov-loop correlators are extrapolated to the continuum limit.
Recent advances in heavy quark theory
Wise, M. [California Institute of Technology, Pasadena, CA (United States)
1997-01-01
Some recent developments in heavy quark theory are reviewed. Particular emphasis is given to inclusive weak decays of hadrons containing a b quark. The isospin violating hadronic decay D{sub s}* {yields} D{sub s}{sup pi}{sup 0} is also discussed.
CP violation in top-quark physics
German Valencia
2010-07-27
In this talk I review how to search for CP violation in top-quark pair production and decay using T-odd correlations. I discuss two examples which illustrate many of the relevant features: CP violation in a heavy neutral Higgs boson; and CP violating anomalous top-quark couplings. I present some numerical results for the LHC and some for the Tevatron.
Tevatron Top-Quark Combinations and World Top-Quark Mass Combination
Reinhild Yvonne Peters; on behalf of the ATLAS; CDF; CMS; D0 collaborations
2014-11-04
Almost 20 years after its discovery, the top quark is still an interesting particle, undergoing precise investigation of its properties. For many years, the Tevatron proton antiproton collider at Fermilab was the only place to study top quarks in detail, while with the recent start of the LHC proton proton collider a top quark factory has opened. An important ingredient for the full understanding of the top quark is the combination of measurements from the individual experiments. In particular, the Tevaton combinations of single top-quark cross sections, the ttbar production cross section, the W helicity in top-quark decays as well as the Tevatron and the world combination of the top-quark mass are discussed.
M. Bishai
2002-12-13
Heavy quark production cross-sections, correlations and polarizations have been measured at the Collider Detector at Fermilab (CDF) using 118 pb{sup -1} of data collected from the 1992 to 1995 Run I of the Fermilab Tevatron. There is still disagreement between theoretical predictions of bottom and charm hadro-production cross-sections and the Run I results. The observed transverse momentum spectrum of the prompt J/{psi} production polarization is still not understood. Run II of the Tevatron began in July of 2001 and the CDF Run II detector [11] has collected 70 pb{sup -1} of physics quality data since January 2002. Large statistics of onia states have been collected. Exclusive B meson decay modes have been reconstructed and the SVT level 2 displaced track trigger has produced large samples of D mesons. The prompt charm and b {yields} cX fractions in both charmonium and D meson samples have been measured. Run II is now poised to greatly enhance the knowledge of heavy quark production dynamics well beyond the reach of the Run I detector.
Kaczmarek, O
2005-01-01
We analyze the change in free energy, internal energy and entropy due to the presence of a heavy quark anti-quark pair in a QCD heat bath. The internal energies and entropies are introduced as intensive observables calculated through thermal derivatives of the QCD partition function containing additional static color sources. The quark anti-quark internal energy and, in particular, the entropy clearly signal the phase change from quark confinement below and deconfinement above the transition and both observables are introduced such that they survive the continuum limit. The intermediate and large distance behavior of the energies reflect string breaking and color screening phenomena. This is used to characterize the energies which are needed to dissolve heavy quarkonium states in a thermal medium. Our discussion supports recent findings which suggest that parts of the quarkonium systems may survive the phase transition and dissolve only at higher temperatures.
The QCD spectrum with three quark flavors
Claude Bernard; Tom Burch; Thomas A. DeGrand; Saumen Datta; Carleton DeTar; Steven Gottlieb; Urs M. Heller; Kostas Orginos; Robert Sugar; Doug Toussaint
2001-05-29
We present results from a lattice hadron spectrum calculation using three flavors of dynamical quarks - two light and one strange, and quenched simulations for comparison. These simulations were done using a one-loop Symanzik improved gauge action and an improved Kogut-Susskind quark action. The lattice spacings, and hence also the physical volumes, were tuned to be the same in all the runs to better expose differences due to flavor number. Lattice spacings were tuned using the static quark potential, so as a byproduct we obtain updated results for the effect of sea quarks on the static quark potential. We find indications that the full QCD meson spectrum is in better agreement with experiment than the quenched spectrum. For the 0++ (a0) meson we see a coupling to two pseudoscalar mesons, or a meson decay on the lattice.
Gluon saturation and Feynman scaling in leading neutron production
Carvalho, F; Spiering, D; Navarra, F S
2015-01-01
In this paper we extend the color dipole formalism to the study of leading neutron production in $e + p \\rightarrow e + n + X$ collisions at high energies and estimate the related observables, which were measured at HERA and may be analysed in future electron-proton ($ep$) colliders. In particular, we calculate the Feynman $x_F$ distribution of leading neutrons, which is expressed in terms of the pion flux and the photon-pion total cross section. In the color dipole formalism, the photon-pion cross section is described in terms of the dipole-pion scattering amplitude, which contains information about the QCD dynamics at high energies and gluon saturation effects. We consider different models for the scattering amplitude, which have been used to describe the inclusive and diffractive $ep$ HERA data. Moreover, the model dependence of our predictions with the description of the pion flux is analysed in detail. We show that the recently released H1 leading neutron spectra can be reproduced using the color dipole ...
Baryon Dissociation in a Strongly Coupled Plasma
Chethan Krishnan
2008-11-14
Using the dual string theory, we study a circular baryonic configuration in a wind of strongly coupled N=4 Yang-Mills plasma blowing in the plane of the baryon, before and after a quark has dissociated from it. A simple enough model that captures many interesting features is when there are four quarks in the baryon. As a step towards phenomenology, we compare representative dissociated configurations, and make some comments about their energetics and other properties. Related results that we find include the observation that the screening length formula L_s T ~ (1-v^2)^{1/4} obtained previously for other color singlet configurations, is robust for circular baryons as well.
Screening length in plasma winds
Elena Caceres; Makoto Natsuume; Takashi Okamura
2007-06-04
We study the screening length L_s of a heavy quark-antiquark pair in strongly coupled gauge theory plasmas flowing at velocity v. Using the AdS/CFT correspondence we investigate, analytically, the screening length in the ultra-relativistic limit. We develop a procedure that allows us to find the scaling exponent for a large class of backgrounds. We find that for conformal theories the screening length is (boosted energy density)^{-1/d}. As examples of conformal backgrounds we study R-charged black holes and Schwarzschild-anti-deSitter black holes in (d+1)-dimensions. For non-conformal theories, we find that the exponent deviates from -1/d and as examples we study the non-extremal Klebanov-Tseytlin and Dp-brane geometries. We find an interesting relation between the deviation of the scaling exponent from the conformal value and the speed of sound.
Messner, R. [Stanford Univ., CA (United States)
1997-01-01
This report covers preliminary measurements from SLD on heavy quark production at the Z{sup 0}, using 150,000 hadronic Z{sup 0} decays accumulated during the 1993-1995 runs. A measurement of R{sub b} with a lifetime double tag is presented. The high electron beam polarization of the SLC is employed in the direct measurement of the parity-violating parameters A{sub b} and A{sub c} by use of the left-right forward-backward asymmetry. The lifetimes of B{sup +} and B{sup 0} mesons have been measured by two analyses. The first identifies semileptonic decays of B mesons with high (p,p{sub t}) leptons; the second analysis isolates a sample of B meson decays with a two-dimensional impact parameter tag and reconstructs the decay length and charge using a topological vertex reconstruction method.
A MEASUREMENT OF THE TOP QUARK'S CHARGE Zeynep Gunay Unalan
Quigg, Chris
advisor Kirsten Tollefson for her guidance, explaining to me the detector and trigger system and truly to confirm if the observed top quark is really the top quark posited in the Standard Model (SM) is to measure its electric charge. In the Standard Model the top quark is the isospin partner of the bottom quark
Top Quark Pair Production in Early CMS Data
Kao, Shih-Chuan
2011-01-01
23 2.13 top decay . . . . . . . . . . . . .of the Top Quark . . . . . . . . . . . . . . . . . . . . .20 Top Production in Hadron
Top Quark Physics at the ILC: Methods and Meanings
Zack Sullivan
2009-03-06
The physics case for studying top-quark physics at the International Linear Collider is well established. This summary places in context the top-quark physics goals, examines the current state-of-the art in understanding of the top-quark mass, and identifies some areas in which the study of the top-quark mass enhances our understanding of new techniques.
Singlet Free Energies of a Static Quark-Antiquark Pair
Konstantin Petrov
2004-09-01
We study the singlet part of the free energy of a static quark anti-quark pair at finite temperature in three flavor QCD with degenerate quark masses using $N_{\\tau}=4$ and 6 lattices with Asqtad staggered fermion action. We look at thermodynamics of the system around phase transition and study its scaling with lattice spacing and quark masses.
Search for Fourth Generation Quarks at CMS
Michael M. H. Luk
2011-10-26
We summarise the analyses that search for fourth generation quarks at the Central Muon Solenoid (CMS) experiment. Such particles provide a natural extension to the Standard Model (SM) and are still consistent with precision electroweak measurements. Our searches are not limited to fourth generation chiral quarks and are relevant to many Beyond the Standard Model theories. No excess over the expected SM background is observed in any of these analyses and limits are set on the masses of the $b^\\prime$ and $t^\\prime$ quarks at 95% confidence level at 361 GeV/$c^2$ and 450 GeV/$c^2$, respectively.
Top Quark Forward-Backward Asymmetry
Kingman Cheung; Wai-Yee Keung; Tzu-Chiang Yuan
2009-11-17
The recent forward-backward asymmetry recorded by the CDF Collaboration for the top and anti-top quark pair production indicates more than $2\\sigma$ deviation from the Standard Model prediction, while its total production cross section remains consistent. We propose a $W'$ boson that couples to down and top quarks. We identify the parameter space that can give rise a large enough forward-backward asymmetry without producing too many top and anti-top quark pairs. Other models presented erstwhile in the literature that can produce such effects are also discussed.
A. M. Green; C. Michael; J. E. Paton
1992-09-15
Four-quark potentials for $SU(2)$ are evaluated in the static limit with the quenched approximation -- using a lattice of $16^3\\times 32$ and $\\beta=2.4$. The four quarks are restricted to the corners of rectangles with sides upto seven lattice spacings long. The results are analysed in terms of a strategy based on interquark two-body potentials -- as advocated earlier by the authors. This shows that a standard two-body approach overestimates the four-quark binding energy by upto a factor of about three for the largest rectangles.
Deconfinement phase transition and the quark condensate
Christian S. Fischer
2009-07-27
We study the dual quark condensate as a signal for the confinement-deconfinement phase transition of QCD. This order parameter for center symmetry has been defined recently by Bilgici et al. within the framework of lattice QCD. In this work we determine the ordinary and the dual quark condensate with functional methods using a formulation of the Dyson-Schwinger equations for the quark propagator on a torus. The temperature dependence of these condensates serves to investigate the interplay between the chiral and deconfinement transitions of quenched QCD.
Static strings in Randall-Sundrum scenarios and the quark anti-quark potential: Erratum
Henrique Boschi-Filho; Nelson R. F. Braga; Cristine N. Ferreira
2006-10-11
We correct the energy of the static strings in hep-th/0512295, for large quark anti-quark separation. This energy is a smooth function of the quark separation for any position of the infrared brane. The asymptotic behavior of this energy is that of the Cornell potential as stated in the article. However, this identification does not fixes the AdS radius.
Heavy Quark Anti-Quark Free Energy and the Renormalized Polyakov Loop
Kaczmarek, O; Petreczky, P; Zantow, F
2002-01-01
We calculate the colour averaged and colour singlet free energies of static quark anti-quark sources placed in a thermal gluonic heat bath. We discuss the renormalization of these free energies using the short distance properties of the zero temperature heavy quark potential. This leads to the definition of the renormalized Polyakov loop as an order parameter for the deconfinement phase transition of the SU(3) gauge theory which is well behaved in the continuum limit.
Asymptotic freedom in the front-form Hamiltonian for quantum chromodynamics of gluons
Maria Gomez-Rocha; Stanislaw D. Glazek
2015-05-25
Asymptotic freedom of gluons in QCD is obtained in the leading terms of their renormalized Hamiltonian in the Fock space, instead of considering virtual Green's functions or scattering amplitudes. Namely, we calculate the three-gluon interaction term in the front-form Hamiltonian for effective gluons in the Minkowski space-time using the renormalization group procedure for effective particles (RGPEP), with a new generator. The resulting three-gluon vertex is a function of the scale parameter, $s$, that has an interpretation of the size of effective gluons. The corresponding Hamiltonian running coupling constant, $g_\\lambda$, depending on the associated momentum scale $\\lambda = 1/s$, is calculated in the series expansion in powers of $g_0 = g_{\\lambda_0}$ up to the terms of third order, assuming some small value for $g_0$ at some large $\\lambda_0$. The result exhibits the same finite sensitivity to small-$x$ regularization as the one obtained in an earlier RGPEP calculation, but the new calculation is simpler than the earlier one because of a simpler generator. This result establishes a degree of universality for pure-gauge QCD in the RGPEP.
Recent Results of Top Quark Physics from the Tevatron
R. Y. Peters; on behalf of the D0; CDF collaborations
2015-07-09
Twenty years after its discovery in 1995 by the CDF and D0 collaborations at the Tevatron proton-antiproton collider at Fermilab, the top quark still undergoes intensive studies at the Tevatron and the LHC at CERN. In this article, recent top quark physics results from CDF and D0 are reported. In particular, measurements of single top quark and double top quark production, the ttbar forward-backward asymmetry and the top quark mass are discussed.
Quenched hadron spectroscopy with improved staggered quark action
MILC Collaboration; Claude Bernard; Tom Blum; Thomas A. DeGrand; Carleton DeTar; Steven Gottlieb; Urs M. Heller; James Hetrick; Craig McNeile; K. Rummukainen; Bob Sugar; Doug Toussaint
1997-12-11
We investigate light hadron spectroscopy with an improved quenched staggered quark action. We compare the results obtained with an improved gauge plus an improved quark action, an improved gauge plus standard quark action, and the standard gauge plus standard quark action. Most of the improvement in the spectroscopy results is due to the improved gauge sector. However, the improved quark action substantially reduces violations of Lorentz invariance, as evidenced by the meson dispersion relations.
Relativistic harmonic oscillator model for quark stars
Vishnu M. Bannur
2008-10-06
The relativistic harmonic oscillator (RHO) model of hadrons is used to study quark stars. The mass-radius relationship is obtained and compared with bag model of quark star, using Tolman-Oppenheimer-Volkoff equation. In this model, the outward degenerate pressure due to discrete Landau levels and Landau degeneracy balances the inward gravitational pressure. Where as in bag model the degenerate pressure is due to the standard continuum levels which balances the combined inward pressure due to gravitation and bag pressure. So in RHO model, the confinement effect is included in the degenerate pressure. We found a qualitative similarity, but quantitative differences in mass-radius relationship of quark stars in these two models. Masses and radii are relatively larger and the central energy densities, required for stable quark stars, are lower in RHO model than that of bag model.
Collider signature of T-quarks
Carena, Marcela; Hubisz, Jay; /Fermilab; Perelstein, Maxim; /Cornell U., LEPP; Verdier, Patrice; /Lyon, IPN
2006-10-01
Little Higgs models with T Parity contain new vector-like fermions, the T-odd quarks or ''T-quarks'', which can be produced at hadron colliders with a QCD-strength cross section. Events with two acoplanar jets and large missing transverse energy provide a simple signature of T-quark production. We show that searches for this signature with the Tevatron Run II data can probe a significant part of the Little Higgs model parameter space not accessible to previous experiments, exploring T-quark masses up to about 400 GeV. This reach covers parts of the parameter space where the lightest T-odd particle can account for the observed dark matter relic abundance. We also comment on the prospects for this search at the Large Hadron Collider (LHC).
Theory of top quark production and decay
Kuehn, J.H. [Universitaet Karlsruhe (Germany)
1997-01-01
Direct and indirect information on the top quark mass and its decay modes is reviewed. The theory of top production in hadron- and electron-positron-colliders is presented.
Charmonium with three flavors of synamical quarks
Massimo Di Pierro et al.
2003-12-23
We present a calculation of the charmonium spectrum with three flavors of dynamical staggered quarks from gauge configurations that were generated by the MILC collaboration. We use the Fermilab action for the valence charm quarks. Our calculation of the spin-averaged 1P-1S and 2S-1S splittings yields a determination of the strong coupling, with {alpha}{sub {ovr MS}}(M{sub Z}) = 0.119(4).
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Prompt Multi-Gluon Production in High Energy Collisions from Singular Yang-Mills Solutions
Romuald A. Janik; Edward Shuryak; Ismail Zahed
2002-06-03
We study non-perturbative parton-parton scattering in the Landau method using singular O(3) symmetric solutions to the Euclidean Yang-Mills equations. These solutions combine instanton dynamics (tunneling) and overlap (transition) between incoming and vacuum fields. We derive a high-energy solution at small Euclidean times, and assess its susequent escape and decay into gluons in Minkowski space-time. We describe the spectrum of the {\\it outgoing} gluons and show that it is related through a particular rescaling to the Yang-Mills sphaleron explosion studied earlier. We assess the number of {\\it incoming} gluons in the same configuration, and argue that the observed scaling is in fact more general and describes the energy dependence of the spectra and multiplicities at {\\it all} energies. Applications to hadron-hadron and nucleus-nucleus collisions are discussed elsewhere.
White, C D; Thorne, Robert S
) = ?S ? ? 0 dk2 k2 hi(k2/Q2)f(N, k2, Q20)gB(N,Q 2 0), (1) where gB is the bare gluon distribution at momentum scale Q20, and the strong coupling ?S is fixed at LL order. The hi(k2/Q2) are the impact factors coupling the virtual photon to the gluon... )gB(N,Q 2 0), (2) which serves to define the impact factor h2. In a general factorisation scheme, one loses the simple inter- pretation of h2 as the coefficient function relating the gluon distribution to the structure function. Instead it represents...
Heavy-light quarks interactions in QCD vacuum
Mirzayusuf Musakhanov
2015-03-20
QCD vacuum instantons induce very strong interactions between light quarks, which generate large dynamical light quark mass M for initially almost massless quarks and can bound these quarks to produce almost massless pions in accordance with the spontaneous breaking of chiral symmetry (S\\chiSB). On the other hand, the QCD vacuum instantons generate heavy-light quark interactions terms, which are responsible for the effects of S\\chiSB in a heavy-light quark system. Summing the re-scattering series that lead to the total light quark propagator and making few further steps, we get the fermionized representation of low-frequencies light quark determinant in the presence of the quark sources, which is relevant for our problems. The next important step in the line of this strategy is to derive the equation and calculate the heavy quark propagator in the instanton media and in the presence of light quarks. This one provide finally the heavy and N_f light quarks interaction term. As an example, we derive heavy quark-light mesons interaction term for the N_f=2 case. If we take the average instanton size \\rho=0.35 fm, and average inter-instanton distance R=0.856 fm from our previous estimates, we obtain at LO on 1/N_c expansion dynamical light quark mass M = 570 MeV and instanton media contribution to heavy quark mass \\Delta M=148 MeV. These factors define the coupling between heavy and light quarks and, certainly, between heavy quarks and light mesons. We will apply this approach to heavy quark and heavy-light quark systems.
Gluon saturation and pseudo-rapidity distributions of charged hadrons at RHIC energy regions
Xin-Bin Wei; Sheng-Qin Feng
2014-11-20
We modified the gluon saturation model by rescaling the momentum fraction according to saturation momentum and introduced the Cooper-Frye hydrodynamic evolution to systematically study the pseudo-rapidity distributions of final charged hadrons at different energies and different centralities for Au-Au collisions in relativistic heavy-ion collisions at BNL Relativistic Heavy Ion Collider (RHIC). The features of both gluon saturation and hydrodynamic evolution at different energies and different centralities for Au-Au collisions are investigated in this paper.
Gluon Sivers Function and Single Spin Asymmetry in $e+p^\\uparrow \\rightarrow e+J/\\psi + X$
Godbole, Rohini M; Mukherjee, Asmita; Rawoot, Vaibhav S
2012-01-01
We propose measurement of transverse single spin asymmetry (SSA) in charmonium production as a probe of gluon Sivers function. We estimate SSA in low virtuality electroproduction of $J/\\psi $ using color evaporation model of charmonium production and existing models of the gluon Sivers function and find sizable asymmetry at JLab, HERMES, COMPASS and eRHIC energies.
Gluon Sivers Function and Single Spin Asymmetry in $e+p^\\uparrow \\rightarrow e+J/?+ X$
Rohini M. Godbole; Anuradha Misra; Asmita Mukherjee; Vaibhav S. Rawoot
2012-10-03
We propose measurement of transverse single spin asymmetry (SSA) in charmonium production as a probe of gluon Sivers function. We estimate SSA in low virtuality electroproduction of $J/\\psi $ using color evaporation model of charmonium production and existing models of the gluon Sivers function and find sizable asymmetry at JLab, HERMES, COMPASS and eRHIC energies.
Chang-Hwan Lee; Ismail Zahed
2014-03-07
We discuss the general features of the electromagnetic radiation from a thermal hadronic gas as constrained by chiral symmetry. The medium effects on the electromagnetic spectral functions and the partial restoration of chiral symmetry are quantified in terms of the pion densities. The results are compared with the electromagnetic radiation from a strongly interacting quark-gluon plasma in terms of the leading gluon condensate operators. We use the spectral functions as constrained by the emission rates to estimate the electric conductivity, the light flavor susceptibility and diffusion constant across the transition from the correlated hadronic gas to a strongly interacting quark-gluon plasma.
Color superconductivity and dense quark matter
Massimo Mannarelli
2008-12-26
The properties of cold and dense quark matter have been the subject of extensive investigation, especially in the last decade. Unfortunately, we still lack of a complete understanding of the properties of matter in these conditions. One possibility is that quark matter is in a color superconducting phase which is characterized by the formation of a diquark condensate. We review some of the basic concepts of color superconductivity and some of the aspects of this phase of matter which are relevant for compact stars. Since quarks have color, flavor as well as spin degrees of freedom many different color superconducting phases can be realized. At asymptotic densities QCD predicts that the color flavor locked phase is favored. At lower densities where the QCD coupling constant is large, perturbative methods cannot be applied and one has to rely on some effective model, eventually trying to constrain such a model with experimental observations. The picture is complicated by the requirement that matter in the interior of compact stars is in weak equilibrium and neutral. These conditions and the (possible) large value of the strange quark mass conspire to separate the Fermi momenta of quarks with different flavors, rendering homogenous superconducting phases unstable. One of the aims of this presentation is to introduce non-experts in the field to some of the basic ideas of color superconductivity and to some of its open problems.
Physics Beyond the Single Top Quark Observation
Heinson, A.P.; Collaboration, for the DZero
2010-10-01
In March 2009, the D0 Collaboration first observed the electroweak production of single top quarks at 5{sigma} significance. We measured the cross section for the combined s-channel and t-channel production modes, and set a lower limit on the CKM matrix element |V{sub tb}|. Since then, we have used the same dataset to measure the t-channel production mode independently, the combined cross section in the hadronically-decaying tau lepton final state, and the width and lifetime of the top quark, and we have set upper limits on contributions from anomalous flavor-changing neutral currents. This paper describes these new measurements, as presented at the 3rd International Workshop on Top Quark Physics, held in Brugge, Belgium, May 31-June 4, 2010.
Top quark mass measurements at CDF
Brubaker, Erik; /Chicago U., EFI
2006-05-01
The mass of the top quark M{sub top} is interesting both as a fundamental parameter of the standard model and as an important input to precision electroweak tests. The Collider Detector at Fermilab (CDF) has a robust program of top quark mass analyses, including the most precise single measurement, M{sub top} = 173.4 {+-} 2.8 GeV/c{sup 2}, using 680 pb{sup -1} of p{bar p} collision data. A combination of current results from CDF gives M{sub top} = 172.0 {+-} 2.7 GeV/c{sup 2}, surpassing the stated goal of 3 GeV/c{sup 2} precision using 2 fb{sup -1} of data. Finally, a combination with current D0 results gives a world average top quark mass of 172.5 {+-} 2.3 GeV/c{sup 2}.
Lattice QCD Thermodynamics with Physical Quark Masses
R. A. Soltz; C. DeTar; F. Karsch; Swagato Mukherjee; P. Vranas
2015-02-08
Over the past few years new physics methods and algorithms as well as the latest supercomputers have enabled the study of the QCD thermodynamic phase transition using lattice gauge theory numerical simulations with unprecedented control over systematic errors. This is largely a consequence of the ability to perform continuum extrapolations with physical quark masses. Here we review recent progress in lattice QCD thermodynamics, focussing mainly on results that benefit from the use of physical quark masses: the crossover temperature, the equation of state, and fluctuations of the quark number susceptibilities. In addition, we place a special emphasis on calculations that are directly relevant to the study of relativistic heavy ion collisions at RHIC and the LHC.
Universality of Quark-Lepton Mass Matrix
Takeshi Fukuyama; Hiroyuki Nishiura
2013-01-22
The recently observed lepton mixing angle $\\theta_{13}$ of the MNS mixing matrix is well incorporated in a universal mixing hypothesis between quark and lepton sectors. This hypothesis asserts that, in the charged lepton diagonal base, all other mass matrices for up- and down-type quarks and light neutrinos are diagonalized by the same unitary matrix except for the phase elements. It is expressed as $V_{CKM}= U_{MNS}(\\delta^\\prime)^\\dagger P U_{MNS}(\\delta)$ for quark mixing matrix $V_{CKM}$ and lepton mixing matrix $U_{MNS}(\\delta)$ in the phenomenological level. Here $P$ is a diagonal phase mass matrix. $\\delta^\\prime$ is a slightly different phase parameter from the Dirac CP violating phase $\\delta=1.1\\pi$ (best fit) in the MNS lepton mixing matrix.
The heavy top quark and supersymmetry
Hall, L.J. [Lawrence Berkeley Lab., CA (United States); [Univ. of California, Berkeley, CA (United States)
1997-01-01
Three aspects of supersymmetric theories are discussed: electroweak symmetry breaking, the issues of flavor, and gauge unification. The heavy top quark plays an important, sometimes dominant, role in each case. Additional symmetries lead to extensions of the Standard Model which can provide an understanding for many of the outstanding problems of particle physics. A broken supersymmetric extension of spacetime allows electroweak symmetry breaking to follow from the dynamics of the heavy top quark; an extension of isospin provides a constrained framework for understanding the pattern of quark and lepton masses; and a grand unified extension of the Standard Model gauge group provides an elegant understanding of the gauge quantum numbers of the components of a generation. Experimental signatures for each of these additional symmetries are discussed.
Short distance physics with heavy quark potentials
Zantow, F; Karsch, Frithjof; Petreczky, P
2002-01-01
We present lattice studies of heavy quark potentials in the quenched approximation of QCD at finite temperatures. Both, the color singlet and color averaged potentials are calculated. While the potentials are well known at large distances, we give a detailed analysis of their short distance behavior (from 0.015 fm to 1 fm) near the critical temperature. At these distances we expect that the T-dependent potentials go over into the zero temperature potential. Indeed, we find evidences that the temperature influence gets suppressed and the potentials starts to become a unique function of the underlying distance scale. We use this feature to normalize the heavy quark potentials at short distances and extract the free energy of the quark system in a gluonic heat bath.
Anomalous radial transport in tokamak edge plasma
Bodi, Vasudeva Raghavendra Kowsik
2010-01-01
Transport in tokamak plasma . . . . . . . . . . . . . . .Numerical simulations of tokamak plasma . . . . . . . . .of blobs in tokamak edge plasmas . . . . . . . . . . . . . .
Motley, R.W.; Glanz, J.
1982-10-25
A device is described for coupling RF power (a plasma sweeper) from RF power introducing means to a plasma having a magnetic field associated therewith comprises at least one electrode positioned near the plasma and near the RF power introducing means. Means are described for generating a static electric field at the electrode directed into the plasma and having a component substantially perpendicular to the plasma magnetic field such that a non-zero vector cross-product of the electric and magnetic fields exerts a force on the plasma causing the plasma to drift.
On Gribov’s supercriticality picture of quark confinement
Williams, Richard
Some years ago Gribov developed the so-called supercritical light-quark confinement scenario. Based on physical arguments he conjectured a drastic change in the analytical properties of the quark propagator when the back ...
Measurement of the top quark pair production cross section in...
Office of Scientific and Technical Information (OSTI)
Measurement of the top quark pair production cross section in proton-proton collisions at sqrts13 TeV Citation Details In-Document Search Title: Measurement of the top quark...
Quark Matter 2006: High-pt and jets
van Leeuwen, Marco
2007-01-01
Quark Matter 2006: High-p T and jets M van Leeuwen LawrenceT particle production and jets in heavy ion collisions fromp T particle production and jet-like correlations from Quark
Top Quark Mass Measurements at the Tevatron
Zhenyu Ye; for CDF; D0 collaborations
2011-07-22
We report the latest results on the top-quark mass and on the top-antitop mass difference from the CDF and D0 collaborations using data collected at the Fermilab Tevatron $p\\bar{p}$ collider at $\\sqrt{s}=1.96$ TeV. We discuss general issues in top-quark mass measurements and present new results from direct measurements and from top-pair production cross-section. We also report new results on the top-antitop mass difference.
Jorgen D'hondt
2007-07-10
The Large Hadron Collider (LHC) is expected to provide proton-proton collisions at a centre-of-mass energy of 14 TeV, yielding millions of of top quark events. The top-physics potential of the two general purpose experiments, ATLAS and CMS, is discussed according to state-of-the-art simulation of both physics and detectors. An overview is given of the most important results with emphasis on the expected improvements in our understanding of physics connected to the top quark.
Quark mass thresholds in QCD thermodynamics
M. Laine; Y. Schroder
2006-05-05
We discuss radiative corrections to how quark mass thresholds are crossed, as a function of the temperature, in basic thermodynamic observables such as the pressure, the energy and entropy densities, and the heat capacity of high temperature QCD. The indication from leading order that the charm quark plays a visible role at surprisingly low temperatures, is confirmed. We also sketch a way to obtain phenomenological estimates relevant for generic expansion rate computations at temperatures between the QCD and electroweak scales, pointing out where improvements over the current knowledge are particularly welcome.
Higgs CP Violation from Vectorlike Quarks
Chen, Chien-Yi; Zhang, Yue
2015-01-01
We explore CP violating aspects in the Higgs sector of models where new vectorlike quarks carry Yukawa couplings mainly to the third generation quarks of the Standard Model. We point out that in the simplest model, Higgs CP violating interactions only exist in the hWW channel. At low energy, we find that rare B decays can place similarly strong constraints as those from electric dipole moments on the source of CP violation. These observations offer a new handle to discriminate from other Higgs CP violating scenarios such as scalar sector extensions of the Standard Model, and imply an interesting future interplay among limits from different experiments.
Review of recent top-quark LHC combinations
Giorgio Cortiana; on behalf of the ATLAS; CMS collaborations within the TOPLHCWG
2014-11-27
A review of recent combinations of top-quark measurements performed at the LHC, by the ATLAS and CMS collaborations, is provided. The typical uncertainty categorisations, and their assumed correlation patterns are presented, together with the results of the combinations of the top-quark pair and single top-quark production cross sections, the top-quark mass, as well as of the $W$ boson polarisation and the charge asymmetry in $t\\bar t$ events.
Light quark spectrum with improved gauge and fermion actions
MILC Collaboration; Claude Bernard; Tom DeGrand; Carleton DeTar; Steven Gottlieb; Urs M. Heller; Jim Hetrick; Craig McNeile; Kari Rummukainen; Bob Sugar; Doug Toussaint; Matthew Wingate
1997-11-08
We report on a study of the light quark spectrum using an improved gauge action and both Kogut-Susskind and Naik quark actions. We have studied six different lattice spacings, corresponding to plaquette couplings ranging from 6.8 to 7.9, with five to six quark masses per coupling. We compare the two quark actions in terms of the spectrum and restoration of flavor symmetry. We also compare these results with those from the conventional action.
Systems of two heavy quarks with effective field theories
Nora Brambilla
2006-09-22
I discuss results and applications of QCD nonrelativistic effective field theories for systems with two heavy quarks.
TOP QUARK PHYSICS AT THE NLC CARL R. SCHMIDT
Schmidt, Carl
TOP QUARK PHYSICS AT THE NLC CARL R. SCHMIDT Santa Cruz Institute for Particle Physics University) is an excellent tool for studying the properties of the top quark. In this talk I review some of the theory of top, is an ideal tool for studying the properties of the top quark. The event environment in e + e \\Gamma
On static quark anti-quark potential at non-zero temperature
A. Bazavov; P. Petreczky
2012-10-23
We study Wilson loops at non-zero temperature and extract the static quark potential from them. The extracted potentials are larger than the singlet free energies and do not show screening for $T<190$ MeV.
Y. Maezawa; S. Aoki; S. Ejiri; T. Hatsuda; N. Ishii; K. Kanaya; N. Ukita; T. Umeda
2010-05-11
Screenings of the quark-gluon plasma in electric and magnetic sectors are studied on the basis of generalized Polyakov-line correlation functions in lattice QCD simulations with two flavors of improved Wilson quarks. Using the Euclidean-time reflection ($\\R$) and the charge conjugation ($\\Ca$), electric and magnetic screening masses are extracted in a gauge invariant manner. Long distance behavior of the standard Polyakov-line correlation in the quark-gluon plasma is found to be dictated by the magnetic screening. Also, ratio of the two screening masses agrees with that obtained from the dimensionally-reduced effective field theory and the ${\\cal N}=4$ supersymmetric Yang-Mills theory.
Top quark property measurements at the LHC
Richard Hawkings
2014-10-29
Measurements of top quark properties performed at the Large Hadron Collider are reviewed, with a particular emphasis on top-pair charge asymmetries, spin correlations and polarization measurements performed by the ATLAS and CMS collaborations. The measurements are generally in good agreement with predictions from next-to-leading-order QCD calculations, and no deviations from Standard Model expectations have been seen.
Effective Field Theory for Top Quark Physics
Cen Zhang; Scott Willenbrock
2010-08-18
Physics beyond the standard model can affect top-quark physics indirectly. We describe the effective field theory approach to describing such physics, and contrast it with the vertex-function approach that has been pursued previously. We argue that the effective field theory approach has many fundamental advantages and is also simpler.
Diquark and light four-quark states
Zhang Ailin [Department of Physics, Shanghai University, Shanghai, 200444 (China); Huang Tao [Institute of High Energy Physics, Chinese Academy of Science, P. O. Box 918 (4), Beijing, 100049 (China); Steele, Tom G. [Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, SK, S7N 5E2 (Canada)
2007-08-01
Four-quark states with different internal clusters are discussed within the constituent quark model. It is pointed out that the diquark concept is not meaningful in the construction of a tetraquark interpolating current in the QCD sum-rule approach, and hence existing sum-rule studies of four-quark states are incomplete. An updated QCD sum-rule determination of the properties of diquark clusters is then used as input for the constituent quark model to obtain the masses of light 0{sup ++} tetraquark states (i.e. a bound state of two diquark clusters). The results support the identification of {sigma}(600), f{sub 0}(980), and a{sub 0}(980) as the 0{sup ++} light tetraquark states, and seem to be inconsistent with the tetraquark state interpretation of the new BES observations of the near-threshold pp enhancements, X(1835) and X(1812), with the possible exception that X(1576) may be an exotic first orbital excitation of f{sub 0}(980) or a{sub 0}(980)
Heavy-quark symmetry and chiral dynamics
Yan, T. (Institute of Physics, Academia Sinica, Taipei, Taiwan 11529 (Taiwan, Province of China) Floyd R. Newman Laboratory of Nuclear Studies, Cornell University, Ithaca, New York 14853 (United States)); Cheng, H.; Cheung, C.; Lin, G. (Institute of Physics, Academia Sinica, Taipei, Taiwan 11529 (Taiwan, Province of China)); Lin, Y.C. (Physics Department, National Central University, Chung-li, Taiwan 32054 (Taiwan, Province of China)); Yu, H. (Institute of Physics, Academia Sinica, Taipei, Taiwan 11529 (Taiwan, Province of China))
1992-08-01
The flavor and spin symmetry of the heavy quarks and the spontaneously broken approximate SU(3){sub {ital L}}{times} SU(3){sub {ital R}} chiral symmetry of the light quarks are exploited to formulate a theory describing the low-energy interactions of the heavy mesons ({ital Q{bar q}} bound states) and heavy baryons ({ital Qq}{sub 1}{ital q2} bound states) with the Goldstone bosons {pi}, {ital K}, and {eta}. The theory contains only three parameters independent of the number of heavy-quark species involved. They can be determined by the decays {ital D}{sup *}{r arrow}{ital D}+{pi}, {Sigma}{sub {ital c}}{r arrow}{Lambda}{sub {ital c}}+{pi}, and {Sigma}{sub {ital c}}{sup *}{r arrow}{Sigma}{sub {ital c}}+{pi}. Theoretically, these coupling constants are related, through partial conservation of axial-vector current, to the axial charges of the heavy mesons and the heavy baryons. They are all calculable in the nonrelativistic quark model by using the spin wave functions of these particles alone. The theory is applied to strong decays and semileptonic weak decays of the heavy mesons and baryons. The implications are also discussed.
Strange quark momentum fraction from overlap fermion
Mingyang Sun; Yi-Bo Yang; Keh-Fei Liu; Ming Gong
2015-03-10
We present a calculation of $_s$ for the strange quark in the nucleon. We also report the ratio of the strange $$ to that of $u/d$ in the disconnected insertion which will be useful in constraining the global fit of parton distribution functions at small $x$. We adopt overlap fermion action on $2 + 1$ flavor domain-wall fermion configurations on the $24^3 \\times 64$ lattice with a light sea quark mass which corresponds to $m_{\\pi}=330$ MeV. Smeared grid $Z_3$ sources are deployed to calculate the nucleon propagator with low-mode substitution. Even-odd grid sources and time-dilution technique with stochastic noises are used to calculate the high mode contribution to the quark loop. Low mode averaging (LMA) for the quark loop is applied to reduce the statistical error of the disconnected insertion calculation. We find the ratio $_s/_{u/d}^{\\mathrm{DI}}= 0.78(3)$ in this study.
Strange quark momentum fraction from overlap fermion
Sun, Mingyang; Liu, Keh-Fei; Gong, Ming
2015-01-01
We present a calculation of $\\langle x \\rangle_s$ for the strange quark in the nucleon. We also report the ratio of the strange $\\langle x \\rangle$ to that of $u/d$ in the disconnected insertion which will be useful in constraining the global fit of parton distribution functions at small $x$. We adopt overlap fermion action on $2 + 1$ flavor domain-wall fermion configurations on the $24^3 \\times 64$ lattice with a light sea quark mass which corresponds to $m_{\\pi}=330$ MeV. Smeared grid $Z_3$ sources are deployed to calculate the nucleon propagator with low-mode substitution. Even-odd grid sources and time-dilution technique with stochastic noises are used to calculate the high mode contribution to the quark loop. Low mode averaging (LMA) for the quark loop is applied to reduce the statistical error of the disconnected insertion calculation. We find the ratio $\\langle x \\rangle_s/\\langle x \\rangle_{u/d}^{\\mathrm{DI}}= 0.78(3)$ in this study.
Quark matter and meson properties in a Nonlocal SU(3) chiral quark model at finite temperature
Gomez Dumm, D.; Contrera, G. A.
2012-06-15
We study the finite temperature behavior of light scalar and pseudoscalar meson properties in the context of a three-flavor nonlocal chiral quark model. The model includes mixing with active strangeness degrees of freedom, and takes care of the effect of gauge interactions by coupling the quarks with a background color field. We analyze the chiral restoration and deconfinement transitions, as well as the temperature dependence of meson masses, mixing angles, and decay constants.
B-physics with dynamical domain-wall light quarks and relativistic b-quarks
Ruth S. Van de Water; Oliver Witzel
2011-01-24
We report on our progress in calculating the B-meson decay constants and B^0-bar B^0 mixing parameters using domain-wall light quarks and relativistic b-quarks. We present our computational method and show some preliminary results obtained on the coarser (a approx 0.11fm) 24^3 lattices. This work is presented on behalf of the RBC and UKQCD collaborations.
Nonlinear plasma wave in magnetized plasmas
Bulanov, Sergei V.; Prokhorov Institute of General Physics, Russian Academy of Sciences, Moscow 119991; Moscow Institute of Physics and Technology, Dolgoprudny, Moscow region 141700 ; Esirkepov, Timur Zh.; Kando, Masaki; Koga, James K.; Hosokai, Tomonao; Zhidkov, Alexei G.; Japan Science and Technology Agency, CREST, 2-1, Yamadaoka, Suita, Osaka 565-0871 ; Kodama, Ryosuke; Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871
2013-08-15
Nonlinear axisymmetric cylindrical plasma oscillations in magnetized collisionless plasmas are a model for the electron fluid collapse on the axis behind an ultrashort relativisically intense laser pulse exciting a plasma wake wave. We present an analytical description of the strongly nonlinear oscillations showing that the magnetic field prevents closing of the cavity formed behind the laser pulse. This effect is demonstrated with 3D PIC simulations of the laser-plasma interaction. An analysis of the betatron oscillations of fast electrons in the presence of the magnetic field reveals a characteristic “Four-Ray Star” pattern.
Velocity Dependence of Baryon Screening in a Hot Strongly Coupled Plasma
Christiana Athanasiou; Hong Liu; Krishna Rajagopal
2008-05-12
The L-dependence of the static potential between Nc quarks arranged in a circle of radius L (a "baryon") immersed in the hot plasma of a gauge theory with Nc colors defines a screening length Ls. We use the AdS/CFT correspondence to compute this screening length for the case of heavy quarks in the plasma of strongly coupled N=4 super Yang-Mills theory moving with velocity v relative to the baryon. We find that in the v -> 1 limit, Ls \\propto (1-v^2)^{1/4}/T, and find that corrections to this velocity dependence are small at lower velocities. This result provides evidence for the robustness of the analogous behavior of the screening length defined by the static quark-antiquark pair, which has been computed previously and in QCD is relevant to quarkonium physics in heavy ion collisions. Our results also show that as long as the hot wind is not blowing precisely perpendicular to the plane of the baryon configuration that we analyze, the Nc different quarks are not all affected by the wind velocity to the same degree, with those quarks lying perpendicular to the wind direction screened most effectively.
Top Quark Properties at the TeVatron
Yvonne Peters for the CDF; D0 Collaborations
2011-03-29
Discovered in 1995 by CDF and D0 at the Fermilab Tevatron collider, the top quark remains interesting to test the Standard Model. Having collected more than 7 fb$^{-1}$ of integrated luminosity with both experiments until today, several top quark properties have been measured with increasing precision, while other properties have been investigated for the first time. In this article recent measurements of top quark properties from CDF and D0 are presented, using between 1 fb$^{-1}$ and 4.8 fb$^{-1}$ of data. In particular, the measurement of the top quark mass, the top quark width, the top antitop mass difference, a check of the electric charge of the top quark, measurements of the top antitop quark spin correlation and W helicity as well as a search for charged Higgs bosons are discussed.
Searching for gluon number fluctuations effects in eA collisions
Kugeratski, M. S.; Gonçalves, V. P.; Santana Amaral, J. T. de
2014-11-11
We propose to investigate the gluon number fluctuations effects in deep inelastic electron-ion scattering at high energies. We estimate the nuclear structure function F{sub 2}{sup A}(x,Q{sup 2}), as well the longitudinal and charm contributions, using a generalization for nuclear targets of the Golec-Biernat-Wusthoff (GBW) model which describes the electron proton HERA data. Here we consider that the nucleus at high energies acts as an amplifier of the physics of high parton densities. For a first investigation we study the scattering with Ca and Pb nuclei. Our preliminary results predict that the effects of gluon number fluctuations are small in the region of the future electron ion collider.
On P_T-distribution of gluon production rate in constant chromoelectric field
D. G. Pak
2007-02-22
A complete expression for the p_T-distribution of the gluon production rate in the homogeneous chromoelectric field has been obtained. Our result contains a new additional term proportional to the singular function \\delta(p_T^2). We demonstrate that the presence of this term is consistent with the dual symmetry of QCD effective action and allows to reproduce the known result for the total imaginary part of the effective action after integration over transverse momentum.
Asymptotic freedom and IR freezing in QCD: the role of gluon paramagnetism
Yu. A. Simonov
2010-11-24
Paramagnetism of gluons is shown to play the basic role in establishing main properties of QCD: IR freezing and asymptotic freedom (AF). Starting with Polyakov background field approach the first terms of background perturbation theory are calculated and shown to ensure not only the classical result of AF but also IR freezing. For the latter only the confining property of the background is needed, and the effective mass entering the IR freezing logarithms is calculated in good agreement with phenomenology and lattice data.
The high-energy limit of H+2 jet production via gluon fusion
V. Del Duca; W. B. Kilgore; C. Oleari; C. R. Schmidt; D. Zeppenfeld
2002-03-16
We consider Higgs + 2 jet production via gluon fusion in the limit where either one of the Higgs-jet or the dijet invariant masses become much larger than the typical momentum transfers in the scattering. These limits also occur naturally in Higgs production via weak-boson fusion. We show that the scattering amplitudes factorize in the high energy limit, and we obtain the relevant effective vertices.
Princeton Plasma Physics Laboratory
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
Plasma Physics Laboratory P.O. Box 451 Princeton, NJ 08543-0451 GPS: 100 Stellarator Road Princeton, NJ 08540 www.pppl.gov 2015 Princeton Plasma Physics Laboratory. A...
Plasma window characterization
Krasik, Ya. E.; Gleizer, S.; Gurovich, V.; Kronhaus, I.; Hershcovitch, A.; Nozar, P.; Taliani, C.
2007-03-01
Parameters of an arc Ar plasma discharge used as a plasma window with a discharge current of {approx}50 A and a voltage of {approx}58 V are presented. It is shown that this arc discharge allows one to decrease the pressure at the low pressure end of the plasma window almost 380 times using relatively low pumping at the low pressure end of the plasma window. Calculations of the plasma parameters and their spatial distribution using a simple wall-stabilized arc model showed a satisfactory agreement with the experimentally obtained data. It is shown that a significant decrease in gas flow through the plasma window occurs due to the increase in plasma viscosity. An improvement of the plasma window ignition and some of its design aspects are described as well.
Ignatov, A.M. [Prokhorov Institute of General Physics, Russian Academy of Sciences, ul. Vavilova 38, Moscow, 119991 (Russian Federation)
2005-01-15
The paper presents an introductory review of the basic physical processes in dusty plasmas. The topics to be addressed are dust charging, forces acting on dust grains, interaction between dust grains, and dust-plasma structures.
C. G. Duan; N. Liu; G. L. Li
2008-11-05
By means of two different parametrizations of quark energy loss and the nuclear parton distributions determined only with lepton-nuclear deep inelastic scattering experimental data, a leading order phenomenological analysis is performed on the nuclear Drell-Yan differential cross section ratios as a function of the quark momentum fraction in the beam proton and target nuclei for E772 experimental data. It is shown that there is the quark energy loss effect in nuclear Drell-Yan process apart from the nuclear effects on the parton distribution as in deep inelastic scattering. The uncertainties due to quark energy loss effect is quantified on determining nuclear sea quark distribution by using nuclear Drell-Yan data. It is found that the quark energy loss effect on nuclear Drell-Yan cross section ratios make greater with the increase of quark momentum fraction in the target nuclei. The uncertainties from quark energy loss become bigger as the nucleus A come to be heavier. The Drell-Yan data on proton incident middle and heavy nuclei versus deuterium would result in an overestimate for nuclear modifications on sea quark distribution functions with neglecting the quark energy loss. Our results are hoped to provide good directional information on the magnitude and form of nuclear modifications on sea quark distribution functions by means of the nuclear Drell-Yan experimental data.
Free energies of heavy quarks in full-QCD lattice simulations with Wilson-type quark action
Y. Maezawa; S. Aoki; S. Ejiri; T. Hatsuda; N. Ishii; K. Kanaya; H. Ohno; T. Umeda
2009-09-16
The free energy between a static quark and an antiquark is studied by using the color-singlet Polyakov-line correlation at finite temperature in lattice QCD with 2+1 flavors of improved Wilson quarks. From the simulations on $32^3 \\times 12$, 10, 8, 6, 4 lattices in the high temperature phase, based on the fixed scale approach, we find that, the heavy-quark free energies at short distance converge to the heavy-quark potential evaluated from the Wilson loop at zero temperature, in accordance with the expected insensitivity of short distance physics to the temperature. At long distance, the heavy-quark free energies approach to twice the single-quark free energies, implying that the interaction between heavy quarks is screened. The Debye screening mass obtained from the long range behavior of the free energy is compared with the results of thermal perturbation theory.
Measuring the Gluon Density in e + A Collisions: KLN CGC, DGLAP Glauber, or Neither?
Horowitz, W A
2011-01-01
We predict readily experimentally measurable differences in the diffractive cross section in the coherent exclusive photoproduction of J/psi mesons in e + A collisions at eRHIC and LHeC energies for nuclear gluon distributions assumed to 1) evolve in x with DGLAP dynamics and have a spatial distribution proportional to the Glauber nuclear thickness function and 2) evolve in x and b according to the KLN prescription of CGC dynamics. We find that CGC physics predicts that the nuclear gluon density widens significantly as a function of x yielding diffractive peaks and minima that evolve dramatically with x; on the other hand the DGLAP Glauber distribution yields peaks and minima constant in x. We also find that the dipole cross section at the level of two gluon exchange within the KLN parameterization of the CGC satisfies the black disk limit whereas this limit is violated when DGLAP evolution is used; the normalization of the diffractive cross section grows more slowly in x by several orders of magnitude when u...
Phase structure and the gluon propagator of SU(2) gauge-Higgs model in two dimensions
Shinya Gongyo; Daniel Zwanziger
2015-01-26
We study numerically the phase structure and the gluon propagator of the SU(2) gauge-Higgs model in two dimensions. First, we calculate gauge-invariant quantities, in particular the static potential from Wilson Loop, the W propagator, and the plaquette expectation value. Our results suggest that a confinement-like region and a Higgs-like region appear even in two dimensions. In the confinement-like region, the static potential rises linearly, with string breaking at large distances, while in the Higgs-like region, it is of Yukawa type, consistent with a Higgs-type mechanism. The correlation length obtained from the W propagator has a finite maximum between these regions. The plaquette expectation value shows a smooth cross-over consistent with the Fradkin-Shenker-Osterwalder-Seiler theorem. From these results, we suggest that there is no phase transition in two dimensions. We also calculate a gauge-dependent order parameter in Landau gauge. Unlike gauge invariant quantities, the gauge non-invariant order parameter has a line of discontinuity separating these two regions. Finally we calculate the gluon propagtor. We infer from its infrared behavior that the gluon propagator would vanish at zero momentum in the infinite-volume limit, consistent with an analytical study.
Measuring the Gluon Density in e + A Collisions: KLN CGC, DGLAP Glauber, or Neither?
W. A. Horowitz
2011-02-24
We predict readily experimentally measurable differences in the diffractive cross section in the coherent exclusive photoproduction of J/psi mesons in e + A collisions at eRHIC and LHeC energies for nuclear gluon distributions assumed to 1) evolve in x with DGLAP dynamics and have a spatial distribution proportional to the Glauber nuclear thickness function and 2) evolve in x and b according to the KLN prescription of CGC dynamics. We find that CGC physics predicts that the nuclear gluon density widens significantly as a function of x yielding diffractive peaks and minima that evolve dramatically with x; on the other hand the DGLAP Glauber distribution yields peaks and minima constant in x. We also find that the dipole cross section at the level of two gluon exchange within the KLN parameterization of the CGC satisfies the black disk limit whereas this limit is violated when DGLAP evolution is used; the normalization of the diffractive cross section grows more slowly in x by several orders of magnitude when using the KLN parameterization as compared to the result when employing DGLAP evolution.
Drag force in strongly coupled, anisotropic plasma at finite chemical potential
Somdeb Chakraborty; Najmul Haque
2014-10-26
We employ methods of gauge/string duality to analyze the drag force on a heavy quark moving through a strongly coupled, anisotropic \\mathcal{N}=4, SU(N) super Yang- Mills plasma in the presence of a finite U(1) chemical potential. We present numerical results valid for any value of the anisotropy parameter and the U(1) charge density and arbitrary direction of the quark velocity with respect to the direction of anisotropy. In the small anisotropy limit we are also able to furnish analytical results.
Multiple Critical Points in Effective Quark Models
Ferroni, Lorenzo; Pinto, Marcus B
2010-01-01
We consider the two flavor version of the Linear Sigma Model as well as of the Nambu Jona-Lasinio model, at finite temperature and quark chemical potential, beyond the Mean Field Approximation. Using parameter values for the pion and quark current masses which weakly break chiral symmetry we show that both models can present more than one critical end point. In particular, we explicitly show that the appearance of a new critical point associated with a first order line at high temperature and low densities could help to conciliate some lattice results with model predictions. Using different techniques, we perform an extensive thermodynamical analysis to understand the physical nature of the different critical points. For both models, our results suggest that the new first order line which starts at vanishing chemical potential has a more chiral character than the usual line which displays a character more reminiscent of a liquid-gas phase transition.
Baryon Spectroscopy and the Constituent Quark Model
A.W. Thomas; R.D. Young
2005-07-26
We explore further the idea that the lattice QCD data for hadron properties in the region m[^2][_pi] > 0.2GeV^2 can be described by the constituent quark model. This leads to a natural explanation of the fact that nucleon excited states are generally stable for pion masses greater than their physical excitation energies. Finally, we apply these same ideas to the problem of how pentaquarks might behave in lattice QCD, with interesting conclusions.
Rare top quark decays in extended models
Gaitan, R.; Miranda, O. G.; Cabral-Rosetti, L. G.
2006-09-25
Flavor changing neutral currents (FCNC) decays t {yields} H0 + c, t {yields} Z + c, and H0 {yields} t + c-bar are discussed in the context of Alternative Left-Right symmetric Models (ALRM) with extra isosinglet heavy fermions where FCNC decays may take place at tree-level and are only suppressed by the mixing between ordinary top and charm quarks, which is poorly constraint by current experimental values. The non-manifest case is also briefly discussed.
Improved lattice fermion action for heavy quarks
Cho, Yong-Gwi; Jüttner, Andreas; Kaneko, Takashi; Marinkovic, Marina; Noaki, Jun-Ichi; Tsang, Justus Tobias
2015-01-01
We develop an improved lattice action for heavy quarks based on Brillouin-type fermions, that have excellent energy-momentum dispersion relation. The leading discretization errors of $O(a)$ and $O(a^2)$ are eliminated at tree-level. We carry out a scaling study of this improved Brillouin fermion action on quenched lattices by calculating the charmonium energy-momentum dispersion relation and hyperfine splitting. We present a comparison to standard Wilson fermions and domain-wall fermions.
Improved lattice fermion action for heavy quarks
Yong-Gwi Cho; Shoji Hashimoto; Andreas Jüttner; Takashi Kaneko; Marina Marinkovic; Jun-Ichi Noaki; Justus Tobias Tsang
2015-05-28
We develop an improved lattice action for heavy quarks based on Brillouin-type fermions, that have excellent energy-momentum dispersion relation. The leading discretization errors of $O(a)$ and $O(a^2)$ are eliminated at tree-level. We carry out a scaling study of this improved Brillouin fermion action on quenched lattices by calculating the charmonium energy-momentum dispersion relation and hyperfine splitting. We present a comparison to standard Wilson fermions and domain-wall fermions.
Moir, Ralph W. (Livermore, CA)
1981-01-01
A mirror plasma apparatus which utilizes shielding by arc discharge to form a blanket plasma and lithium walls to reduce neutron damage to the wall of the apparatus. An embodiment involves a rotating liquid lithium blanket for a tandem mirror plasma apparatus wherein the first wall of the central mirror cell is made of liquid lithium which is spun with angular velocity great enough to keep the liquid lithium against the first material wall, a blanket plasma preventing the lithium vapor from contaminating the plasma.
Quark Nova Model for Fast Radio Bursts
Zachary Shand; Amir Ouyed; Nico Koning; Rachid Ouyed
2015-05-29
FRBs are puzzling, millisecond, energetic radio transients with no discernible source; observations show no counterparts in other frequency bands. The birth of a quark star from a parent neutron star experiencing a quark nova - previously thought undetectable when born in isolation - provides a natural explanation for the emission characteristics of FRBs. The generation of unstable r-process elements in the quark nova ejecta provides millisecond exponential injection of electrons into the surrounding strong magnetic field at the parent neutron star's light cylinder via $\\beta$-decay. This radio synchrotron emission has a total duration of hundreds of milliseconds and matches the observed spectrum while reducing the inferred dispersion measure by approximately 200 cm$^{-3}$ pc. The model allows indirect measurement of neutron star magnetic fields and periods in addition to providing astronomical measurements of $\\beta$-decay chains of unstable neutron rich nuclei. Using this model, we can calculate expected FRB average energies ($\\sim$ 10$^{41}$ ergs), spectra shapes and provide a theoretical framework for determining distances.
The Top Quark - 2006 and Beyond
John Womersley
2006-04-04
We know there is new physics at the electroweak scale, but we don't know what it is. Right now, the top quark is our only window on to this physics. In almost all models of electroweak symmetry breaking, top either couples strongly to new particles or its properties are modified in some way. Top is being studied in detail at the Fermilab Tevatron. Its production cross section has been measured in a variety of channels; its mass has been determined to better than 2%, and can be used to constrain the mass of the Higgs. Top quark decays have been tested and non-standard production mechanisms searched for. Single top production probes the electroweak properties of top, and has not yet been observed; searches are now closing in on this process and it should be seen soon. So far, all of the top quark's properties are consistent with the Standard Model. However, the data still to come at the Tevatron will increase the precision of all these measurements, and the enormous statistics available at the LHC will open up new possibilities such as observation of spin correlations and perhaps even CP violation in the top sector.
Color superconducting quark matter in compact stars
D. B. Blaschke; T. Klahn; F. Sandin
2007-12-02
Recent indications for high neutron star masses (M \\sim 2 M_sun) and large radii (R > 12 km) could rule out soft equations of state and have provoked a debate whether the occurence of quark matter in compact stars can be excluded as well. We show that modern quantum field theoretical approaches to quark matter including color superconductivity and a vector meanfield allow a microscopic description of hybrid stars which fulfill the new, strong constraints. For these objects color superconductivity turns out to be an essential ingredient for a successful description of the cooling phenomenology in accordance with recently developed tests. We discuss the energy release in the neutrino untrapping transition as a new aspect of the problem that hybrid stars masquerade themselves as neutron stars. Quark matter searches in future generations of low-temperature/high-density nucleus-nucleus collision experiments such as low-energy RHIC and CBM @ FAIR might face the same problem of an almost crossover behavior of the deconfinement transition. Therefore, diagnostic tools shall be derived from effects of color superconductivity.
Top quark physics at the Tevatron
Antonio Sidoti
2004-03-17
After the successful Run I of the Tevatron (1992-1996),with the top quark discovery, both CDF and D0 experiments were extensively upgraded to meet the challenges of the Tevatron Run II collider. The energy of p{bar p} collisions at the Tevatron was increased from {radical}s = 1.8 TeV to {radical}s = 1.96 TeV. t{bar t} production cross section is expected to increase by a factor of {approx} 30%. Major upgrades in the Tevatron accelerator chain will increase the Run II instantaneous luminosity: the goal is to achieve L = 5 - 20 x 10{sup 31} cm{sup 2}s{sup -1} while the highest luminosity reached up to now (September 2003) is 5.2 x 10{sup 31} cm{sup 2} s{sup -1}. In this paper we will present the top quark properties measured by both CDF and D0 with the first physics-quality data collected during the Run II (March 2002-January 2003). First we will review t{bar t} cross section measurements in the various decay channels; then top quark mass measurements will be presented.
Domain wall QCD with physical quark masses
RBC,; Blum, T; Boyle, P A; Christ, N H; Frison, J; Garron, N; Hudspith, R J; Izubuchi, T; Janowski, T; Jung, C; Juettner, A; Kelly, C; Kenway, R D; Lehner, C; Marinkovic, M; Mawhinney, R D; McGlynn, G; Murphy, D J; Ohta, S; Portelli, A; Sachrajda, C T; Soni, A
2014-01-01
We present results for several light hadronic quantities ($f_\\pi$, $f_K$, $B_K$, $m_{ud}$, $m_s$, $t_0^{1/2}$, $w_0$) obtained from simulations of 2+1 flavor domain wall lattice QCD with large physical volumes and nearly-physical pion masses at two lattice spacings. We perform a short, O(3)%, extrapolation in pion mass to the physical values by combining our new data in a simultaneous chiral/continuum `global fit' with a number of other ensembles with heavier pion masses. We use the physical values of $m_\\pi$, $m_K$ and $m_\\Omega$ to determine the two quark masses and the scale - all other quantities are outputs from our simulations. We obtain results with sub-percent statistical errors and negligible chiral and finite-volume systematics for these light hadronic quantities, including: $f_\\pi$ = 130.2(9) MeV; $f_K$ = 155.5(8) MeV; the average up/down quark mass and strange quark mass in the $\\overline {\\rm MS}$ scheme at 3 GeV, 2.997(49) and 81.64(1.17) MeV respectively; and the neutral kaon mixing parameter, ...
Domain wall QCD with physical quark masses
RBC; UKQCD collaborations; :; T. Blum; P. A. Boyle; N. H. Christ; J. Frison; N. Garron; R. J. Hudspith; T. Izubuchi; T. Janowski; C. Jung; A. Juettner; C. Kelly; R. D. Kenway; C. Lehner; M. Marinkovic; R. D. Mawhinney; G. McGlynn; D. J. Murphy; S. Ohta; A. Portelli; C. T. Sachrajda; A. Soni
2014-11-25
We present results for several light hadronic quantities ($f_\\pi$, $f_K$, $B_K$, $m_{ud}$, $m_s$, $t_0^{1/2}$, $w_0$) obtained from simulations of 2+1 flavor domain wall lattice QCD with large physical volumes and nearly-physical pion masses at two lattice spacings. We perform a short, O(3)%, extrapolation in pion mass to the physical values by combining our new data in a simultaneous chiral/continuum `global fit' with a number of other ensembles with heavier pion masses. We use the physical values of $m_\\pi$, $m_K$ and $m_\\Omega$ to determine the two quark masses and the scale - all other quantities are outputs from our simulations. We obtain results with sub-percent statistical errors and negligible chiral and finite-volume systematics for these light hadronic quantities, including: $f_\\pi$ = 130.2(9) MeV; $f_K$ = 155.5(8) MeV; the average up/down quark mass and strange quark mass in the $\\overline {\\rm MS}$ scheme at 3 GeV, 2.997(49) and 81.64(1.17) MeV respectively; and the neutral kaon mixing parameter, $B_K$, in the RGI scheme, 0.750(15) and the $\\overline{\\rm MS}$ scheme at 3 GeV, 0.530(11).
Trelles, J P; Vardelle, A; Heberlein, J V R
2013-01-01
Arc plasma torches are the primary components of various industrial thermal plasma processes involving plasma spraying, metal cutting and welding, thermal plasma CVD, metal melting and remelting, waste treatment and gas production. They are relatively simple devices whose operation implies intricate thermal, chemical, electrical, and fluid dynamics phenomena. Modeling may be used as a means to better understand the physical processes involved in their operation. This paper presents an overview of the main aspects involved in the modeling of DC arc plasma torches: the mathematical models including thermodynamic and chemical non-equilibrium models, turbulent and radiative transport, thermodynamic and transport property calculation, boundary conditions and arc reattachment models. It focuses on the conventional plasma torches used for plasma spraying that include a hot-cathode and a nozzle anode.
Top-quark mass measurements: Alternative techniques (LHC + Tevatron)
Stefanie Adomeit
2014-11-28
Measurements of the top-quark mass employing alternative techniques are presented, performed by the D0 and CDF collaborations at the Tevatron as well as the ATLAS and CMS experiments at the LHC. The alternative methods presented include measurements using the lifetime of $B$-hadrons, the transverse momentum of charged leptons and the endpoints of kinematic distributions in top quark anti-quark pair ($t\\bar{t}$) final states. The extraction of the top-quark pole mass from the $t\\bar{t}$ production cross-section and the normalized differential $t\\bar{t}$ + 1-jet cross-section are discussed as well as the top-quark mass extraction using fixed-order QCD predictions at detector level. Finally, a measurement of the top-quark mass using events enhanced in single top t-channel production is presented.
Tsytovich, V N; De Angelis, U; Forlani, A
1995-01-01
Collective plasma effects in scattering of radiation in astrophysical plasmas (Collective plasma processes and the solar neutrino problem)
Static quark anti-quark pair in SU(2) gauge theory
A. Bazavov; P. Petreczky; A. Velytsky
2008-09-11
We study singlet and triplet correlation functions of static quark anti-quark pair defined through gauge invariant time-like Wilson loops and Polyakov loop correlators in finite temperature SU(2) gauge theory. We use the Luescher-Weisz multilevel algorithm, which allows to calculate these correlators at very low temperatures. We observe that the naive separation of singlet and triplet states in general does not hold non-perturbatively, however, is recovered in the limit of small separation and the temperature dependence of the corresponding correlators is indeed very different.
Plasma Camp | Princeton Plasma Physics Lab
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
Plasma Camp December 12, 2013 Due to unforeseen budget cuts, this program has been cancelled for 2014. We are very sorry we cannot offer the program and apologize for the late...
Top quark mass measurements at the D0 experiment
Alexander Grohsjean
2009-05-30
The most recent measurements of the top quark mass at the D0 experiment are summarized. Different techniques and final states are used and the top quark mass is determined to be mtop=172.8+-1.6(stat+syst)GeV/c^2. In addition, a new, indirect measurement comparing the measured cross section to theoretical calculations is discussed. Both, the direct and the indirect measurement of the top quark mass are in good agreement.
QCD Thermodynamics with an almost realistic quark mass spectrum
C. Schmidt
2006-01-25
We will report on the status of a new large scale calculation of thermodynamic quantities in QCD with light up and down quarks corresponding to an almost physical light quark mass value and a heavier strange quark mass. These calculations are currently being performed on the QCDOC Teraflops computers at BNL. We will present new lattice calculations of the transition temperature and various susceptibilities reflecting properties of the chiral transition. All these quantities are of immediate interest for heavy ion phenomenology.
Thermodynamics of QCD at large quark chemical potential
Andreas Gerhold; Andreas Ipp; Anton Rebhan
2005-12-21
We review the existing weak-coupling results on the thermodynamic potential of deconfined QCD at small and large quark chemical potential and compare with results from lattice gauge theory as well as the exactly solvable case of large-N_f QCD. We also discuss the new analytical results on non-Fermi-liquid effects in entropy and specific heat as well as in dispersion laws of quark quasiparticles at large quark chemical potential.
Quark Propagator and Chiral Symmetry with String Tension
Anishetty, R; Anishetty, Ramesh; Kudtarkar, Santosh Kumar
2003-01-01
General properties of the light and heavy quark propagators have been investigated in the context of string tension interaction. Confinement, chiral symmetry breaking, spectral properties of the propagator are analytically studied and numerically validated. We show that the propagator is analytic in the infrared region even for massless quarks with a non zero radius of convergence. Emergence of more than one mass scale is exemplified. Massless limit of the quark propagator does exhibit critical behaviour.
Kirsch, Matthias; /Aachen, Tech. Hochsch.
2009-06-01
At particle accelerators the Standard Model has been tested and will be tested further to a great precision. The data analyzed in this thesis have been collected at the world's highest energetic-collider, the Tevatron, located at the Fermi National Accelerator Laboratory (FNAL) in the vicinity of Chicago, IL, USA. There, protons and antiprotons are collided at a center-of-mass energy of {radical}s = 1.96 TeV. The discovery of the top quark was one of the remarkable results not only for the CDF and D0 experiments at the Tevatron collider, but also for the Standard Model, which had predicted the existence of the top quark because of symmetry arguments long before already. Still, the Tevatron is the only facility able to produce top quarks. The predominant production mechanism of top quarks is the production of a top-antitop quark pair via the strong force. However, the Standard Model also allows the production of single top quarks via the electroweak interaction. This process features the unique opportunity to measure the |V{sub tb}| matrix element of the Cabbibo-Kobayashi-Maskawa (CKM) matrix directly, without assuming unitarity of the matrix or assuming that the number of quark generations is three. Hence, the measurement of the cross section of electroweak top quark production is more than the technical challenge to extract a physics process that only occurs one out of ten billion collisions. It is also an important test of the V-A structure of the electroweak interaction and a potential window to physics beyond the Standard Model in the case where the measurement of |V{sub tb}| would result in a value significantly different from 1, the value predicted by the Standard Model. At the Tevatron two production processes contribute significantly to the production of single top quarks: the production via the t-channel, also called W-gluon fusion, and the production via the s-channel, known as well as W* process. This analysis searches for the combined s+t channel production cross section, assuming the ratio of s-channel production over t-channel production is realized in nature as predicted by the Standard Model. A data set of approximately 1 fb{sup -1} is analyzed, the data set used by the D0 collaboration to claim evidence for single top quark production. Events with two, three, and four jets are used in the analysis if they contain one or two jets that were tagged as originating from the decay of a b hadron, an isolated muon or electron, and a significant amount of missing transverse energy. This selection of events follows the signature that the single top quark events are expected to show in the detector. In the meantime, both collaborations D0 and CDF have analyzed a larger data set and have celebrated the joint observation of single top quark production. The novelty of the analysis presented here is the way discriminating observables are determined. A so-called Multi-Process Factory evaluates each event under several hypotheses. A common analysis technique for example in top quark properties studies is to reconstruct the intermediate particles in the decay chain of the signal process from the final state objects measured in the various subdetectors. An essential part of such a method is to resolve the ambiguities that arise in the assignment of the final state objects to the partons of the decay chain. In a Multi-Process Factory this approach is extended and not only the decay chain of the signal process is reconstructed, but also the decay chains of the most important background processes. From the numerous possible event configurations for each of the signal and background decay chains the most probable configuration is selected based on a likelihood measure. Properties of this configuration, such as mass of the reconstructed top quark, are then used in a multivariate analysis technique to separate the expected signal contribution from the background processes. The technique which is used is called Boosted Decision Trees and has only recently been introduced in high energy physics analyses. A Bayesian approach is use
Evolution equation for 3-quark Wilson loop operator
R. E. Gerasimov; A. V. Grabovsky
2012-12-07
The evolution equation for the 3 quark Wilson loop operator has been derived in the leading logarithm approximation within Balitsky high energy operator expansion.
Electromagnetic form factors and the hypercentral constituent quark model
Sanctis, M. De; Giannini, M. M.; Santopinto, E.; Vassallo, A.
2007-12-15
We present new results concerning the electromagnetic form factors of the nucleon using a relativistic version of the hypercentral constituent quark model and a relativistic current.
Proposal to support junior scientists participation of Quark Matter 2004
Huan Zhong Huang; Kenneth Barish; Hans Georg Ritter
2005-12-15
This report summarizes the student and post-doc support budget for quark matter 2004 conference, held at Oakland in January 2004.
Nucleon sigma term and quark condensate in nuclear matter
K. Tsushima; K. Saito; A. W. Thomas; A. Valcarce
2006-10-10
We study the bound nucleon sigma term and the quark condensate in nuclear matter. In the quark-meson coupling (QMC) model the nuclear correction to the sigma term is small and negative, i.e., it decelerates the decrease of the quark condensate in nuclear matter. However, the quark condensate in nuclear matter is controlled primarily by the scalar-isoscalar $\\sigma$ field. Compared to the leading term, it moderates the decrease more than that of the nuclear sigma term alone at densities around and larger than the normal nuclear matter density.
Dynamical electroweak symmetry breaking and the top quark
Chivukula, R.S. [Boston Univ., MA (United States)
1997-01-01
In this talk, I discuss theories of dynamical electroweak symmetry breaking, with emphasis on the implications of a heavy top quark on the weak interaction {rho} parameter.
From Quarks to the Bomb Basic Science Science Policy
Gilfoyle, Jerry
Jerry Gilfoyle, University of Richmond Outline: 1. Hunting for Quarks: Motivation and Method 2. Nuclear Non-proliferation: Science Meets Politics 3. Science and Policy Careers Research Introductions
Quark Matter 2006: high-pT and jets
M. van Leeuwen
2007-02-06
An overview of new experimental results on high-\\pT{} particle production and jets in heavy ion collisions from the Quark Matter 2006 conference is presented.
Higgs boson gluon-fusion production beyond threshold in N³LO QCD
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Anastasiou, Charalampos; Duhr, Claude; Dulat, Falko; Furlan, Elisabetta; Gehrmann, Thomas; Herzog, Franz; Mistlberger, Bernhard
2015-03-01
In this article, we compute the gluon fusion Higgs boson cross-section at N³LO through the second term in the threshold expansion. This calculation constitutes a major milestone towards the full N³LO cross section. Our result has the best formal accuracy in the threshold expansion currently available, and includes contributions from collinear regions besides subleading corrections from soft and hard regions, as well as certain logarithmically enhanced contributions for general kinematics. We use our results to perform a critical appraisal of the validity of the threshold approximation at N³LO in perturbative QCD.
A manifestation of a gluon saturation in e-A DIS
Levin, E; Levin, Eugene; Maor, Uri
2000-01-01
This is a short presentation of our talks given at eRHIC Workshop at the BNL. We give here a status report of our attempts to understand how gluon saturation will manifest itself in deep inelastic scattering with nuclei. This summary reflects our current understanding and shows directions of our research rather then a final answer to the question. Nevertheless, we are able to share with our reader our tentative answer to the question:``Why do we need to measure DIS with nuclei and why these data will be complementary to the information obtained from proton DIS".
A manifestation of a gluon saturation in e-A DIS
Eugene Levin; Uri Maor
2000-09-19
This is a short presentation of our talks given at eRHIC Workshop at the BNL. We give here a status report of our attempts to understand how gluon saturation will manifest itself in deep inelastic scattering with nuclei. This summary reflects our current understanding and shows directions of our research rather then a final answer to the question. Nevertheless, we are able to share with our reader our tentative answer to the question:``Why do we need to measure DIS with nuclei and why these data will be complementary to the information obtained from proton DIS".
Non-perturbative computation of double inclusive gluon production in the Glasma
Lappi, T; Venugopalan, R
2009-01-01
The near-side ridge observed in A+A collisions at RHIC has been described as arising from the radial flow of Glasma flux tubes formed at very early times in the collisions. We investigate the viability of this scenario by performing a non-perturbative numerical computation of double inclusive gluon production in the Glasma. Our results support the conjecture that the range of transverse color screening of correlations determining the size of the flux tubes is a semi-hard scale, albeit with non-trivial structure. We compare our results to extractions of ridge correlations from the RHIC heavy ion experiments.
Non-perturbative computation of double inclusive gluon production in the Glasma
T. Lappi; S. Srednyak; R. Venugopalan
2010-03-02
The near-side ridge observed in A+A collisions at RHIC has been described as arising from the radial flow of Glasma flux tubes formed at very early times in the collisions. We investigate the viability of this scenario by performing a non-perturbative numerical computation of double inclusive gluon production in the Glasma. Our results support the conjecture that the range of transverse color screening of correlations determining the size of the flux tubes is a semi-hard scale, albeit with non-trivial structure. We discuss our results in the context of ridge correlations in the RHIC heavy ion experiments.
Higgs boson gluon-fusion production beyond threshold in N3LO QCD
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Anastasiou, Charalampos; Duhr, Claude; Dulat, Falko; Furlan, Elisabetta; Gehrmann, Thomas; Herzog, Franz; Mistlberger, Bernhard
2015-03-01
In this article, we compute the gluon fusion Higgs boson cross-section at N3LO through the second term in the threshold expansion. This calculation constitutes a major milestone towards the full N3LO cross section. Our result has the best formal accuracy in the threshold expansion currently available, and includes contributions from collinear regions besides subleading corrections from soft and hard regions, as well as certain logarithmically enhanced contributions for general kinematics. We use our results to perform a critical appraisal of the validity of the threshold approximation at N3LO in perturbative QCD.
Gluon scattering in N=4 super-Yang-Mills theory fromweak to strong coupling
Dixon, Lance J.; /SLAC
2008-03-25
I describe some recent developments in the understanding of gluon scattering amplitudes in N = 4 super-Yang-Mills theory in the large-N{sub c} limit. These amplitudes can be computed to high orders in the weak coupling expansion, and also now at strong coupling using the AdS/CFT correspondence. They hold the promise of being solvable to all orders in the gauge coupling, with the help of techniques based on integrability. They are intimately related to expectation values for polygonal Wilson loops composed of light-like segments.
Initial energy density and gluon distribution from the Glasma in heavy-ion collisions
Hirotsugu Fujii; Kenji Fukushima; Yoshimasa Hidaka
2008-11-04
We estimate the energy density and the gluon distribution associated with the classical fields describing the early-time dynamics of the heavy-ion collisions. We first decompose the energy density into the momentum components exactly in the McLerran-Venugopalan model, with the use of the Wilson line correlators. Then we evolve the energy density with the free-field equation, which is justified by the dominance of the ultraviolet modes near the collision point. We also discuss the improvement with inclusion of nonlinear terms into the time evolution. Our numerical results at RHIC energy are fairly consistent with the empirical values.
Single soft gluon emission at two loops (Journal Article) | SciTech Connect
Office of Scientific and Technical Information (OSTI)
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Single soft gluon emission at two loops (Journal Article) | SciTech Connect
Office of Scientific and Technical Information (OSTI)
AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity of NaturalDukeWakefieldSulfateSciTechtail. (Conference)Feedback System in the CERN SPS (Conference)Single soft gluon
Flavor Physics in the Quark Sector
Antonelli, Mario; /Frascati; Asner, David Mark; /Carleton U.; Bauer, Daniel Adams; /Imperial Coll., London; Becher, Thomas G.; /Fermilab; Beneke, M.; /Aachen, Tech. Hochsch.; Bevan, Adrian John; /Queen Mary, U. of London; Blanke, Monika; /Munich, Tech. U. /Munich, Max Planck Inst.; Bloise, C.; /Frascati; Bona, Marcella; /CERN; Bondar, Alexander E.; /Novosibirsk, IYF; Bozzi, Concezio; /INFN, Ferrara; Brod, Joachim; /Karlsruhe U.; Buras, Andrzej J.; /Munich, Tech. U.; Cabibbo, N.; /INFN, Rome /Rome U.; Carbone, A.; /INFN, Bologna; Cavoto, Gianluca; /INFN, Rome; Cirigliano, Vincenzo; /Los Alamos; Ciuchini, Marco; /INFN, Rome; Coleman, Jonathon P.; /SLAC; Cronin-Hennessy, Daniel P.; /Minnesota U.; Dalseno, J.P.; /KEK, Tsukuba /Glasgow U. /Queen Mary, U. of London /Freiburg U. /Charles U. /Pisa U. /Vienna, OAW /Imperial Coll., London /Bergen U. /INFN, Rome /Rome U. /Munich, Tech. U. /INFN, Rome /Rome U. /Southampton U. /INFN, Rome /Nara Women's U. /Florida U. /INFN, Turin /Turin U. /Edinburgh U. /Warwick U. /INFN, Rome /Rome U. /Massachusetts U., Amherst /KEK, Tsukuba /Bern U. /CERN /Munich, Tech. U. /Mainz U., Inst. Phys. /Wayne State U. /Munich, Max Planck Inst. /CERN /Frascati /Brookhaven /Mainz U., Inst. Kernphys. /Munich, Tech. U. /Siegen U. /Imperial Coll., London /Victoria U. /KEK, Tsukuba /Fermilab /Washington U., St. Louis /Frascati /Warwick U. /Indian Inst. Tech., Madras /Melbourne U. /Princeton U. /Beijing, Inst. High Energy Phys. /INFN, Rome /INFN, Rome3 /Fermilab /SLAC /York U., Canada /Brookhaven /UC, Irvine /INFN, Rome /Rome U. /Valencia U., IFIC /INFN, Padua /Padua U. /Munich, Max Planck Inst. /Barcelona U. /Warwick U. /Tata Inst. /Frascati /Mainz U., Inst. Phys. /Vienna U. /KEK, Tsukuba /Orsay, LPT /Frascati /Munich, Tech. U. /Brookhaven /Bern U. /CERN /Mainz U., Inst. Phys. /Wayne State U. /Valencia U., IFIC /CERN /Kentucky U. /Oxford U. /Iowa State U. /Bristol U. /INFN, Rome /Rutherford /CERN /Orsay, LAL /Glasgow U. /INFN, Padua /Queen Mary, U. of London /Texas U. /LPHE, Lausanne /Fermilab /UC, Santa Cruz /Vienna, OAW /Cincinnati U. /Frascati /Orsay, LAL /Ohio State U. /Purdue U. /Novosibirsk, IYF /Frascati /INFN, Rome /Padua U. /INFN, Rome /Bern U. /Karlsruhe U. /Brookhaven /CERN /Paris U., VI-VII /Zurich, ETH /Pisa U. /Frascati /Oxford U. /Orsay, LAL /INFN, Rome2 /INFN, Rome /INFN, Rome3 /Princeton U. /Fermilab /Queen's U., Kingston /KEK, Tsukuba /Melbourne U. /Brookhaven /Indiana U. /INFN, Rome /Rome U. /Pisa U. /Mainz U., Inst. Phys. /Karlsruhe U. /Oxford U. /Cambridge U., DAMTP /Edinburgh U. /CERN
2010-08-26
In the past decade, one of the major challenges of particle physics has been to gain an in-depth understanding of the role of quark flavor. In this time frame, measurements and the theoretical interpretation of their results have advanced tremendously. A much broader understanding of flavor particles has been achieved, apart from their masses and quantum numbers, there now exist detailed measurements of the characteristics of their interactions allowing stringent tests of Standard Model predictions. Among the most interesting phenomena of flavor physics is the violation of the CP symmetry that has been subtle and difficult to explore. In the past, observations of CP violation were confined to neutral K mesons, but since the early 1990s, a large number of CP-violating processes have been studied in detail in neutral B mesons. In parallel, measurements of the couplings of the heavy quarks and the dynamics for their decays in large samples of K,D, and B mesons have been greatly improved in accuracy and the results are being used as probes in the search for deviations from the Standard Model. In the near future, there will be a transition from the current to a new generation of experiments, thus a review of the status of quark flavor physics is timely. This report is the result of the work of the physicists attending the 5th CKM workshop, hosted by the University of Rome 'La Sapienza', September 9-13, 2008. It summarizes the results of the current generation of experiments that is about to be completed and it confronts these results with the theoretical understanding of the field which has greatly improved in the past decade.
Algebraic Quarks from the Tangent Bundle: Methodology
Jose G. Vargas
2015-09-29
In a previous paper, we developed a table of components of algebraic solutions of a system of equations generated by an inhomogeneous proper-value equation involving K\\"ahler's total angular momentum. This table looks as if it were a representation of real life quarks. We did not consider all options for solutions of the system of equations that gave rise to it. We shall not, therefore, claim that the present distribution of those components as a well ordered table has strict physical relevance. It, however, is of great interest for the purpose of developing methodology, which may then be used for other solutions. We insert into our present table concepts that parallel those of the phenomenology of HEP: generations, color, flavor, isospin, etc. Breaking then loose from that distribution, we consider simpler alternatives for algebraic "quarks" of primary color (The mathematics speaks of each generation having its own primary color). We use them to show how stoichiometric argument allows one to reach what appear to be esthetically appealing idempotent representation of particles for other than electrons and positrons (K\\"ahler already provided these half a century ago with idempotents similar to our hypothetical quarks). We then use neutron decay to obtain formulas for also hypothetical algebraic neutrinos and the $Z_{0}$, and use pair annihilation to obtain formulas for gamma particles. We go back to the system of equations and develop an alternative option. We solve the system but stop short of studying it along the present line. This will thus be an easy entry point to this theory by HEP physicists, who will be able to go aster and further.
Top Quark Spin Correlations at the Tevatron
Head, Tim; /Manchester U.
2010-07-01
Recent measurements of the correlation between the spin of the top and the spin of the anti-top quark produced in proton anti-proton scattering at a center of mass energy of {radical}s = 1.96 Tev by the CDF and D0 collaborations are discussed. using up to 4.3 fb{sup -1} of data taken with the CDF and D0 detectors the spin correlation parameter C, the degree to which the spins are correlated, is measured in dileptonic and semileptonic final states. The measurements are found to be in agreement with Standard Model predictions.
Photon emission from bare quark stars
B. G. Zakharov
2010-08-16
We investigate the photon emission from the electrosphere of a quark star. It is shown that at temperatures T\\sim 0.1-1 MeV the dominating mechanism is the bremsstrahlung due to bending of electron trajectories in the mean Coulomb field of the electrosphere. The radiated energy for this mechanism is much larger than that for the Bethe-Heitler bremsstrahlung. The energy flux from the mean field bremsstrahlung exceeds the one from the tunnel e^{+}e^{-} pair creation as well. We demonstrate that the LPM suppression of the photon emission is negligible.
Plasma Processing Of Hydrocarbon
Grandy, Jon D; Peter C. Kong; Brent A. Detering; Larry D. Zuck
2007-05-01
The Idaho National Laboratory (INL) developed several patented plasma technologies for hydrocarbon processing. The INL patents include nonthermal and thermal plasma technologies for direct natural gas to liquid conversion, upgrading low value heavy oil to synthetic light crude, and to convert refinery bottom heavy streams directly to transportation fuel products. Proof of concepts has been demonstrated with bench scale plasma processes and systems to convert heavy and light hydrocarbons to higher market value products. This paper provides an overview of three selected INL patented plasma technologies for hydrocarbon conversion or upgrade.
Office of Environmental Management (EM)
23-25, 2014 2 Safety concern: "in-vessel inventory source term" * Challenges in neutron-irradiated plasma facing components (PFCs) - Radiation damages (vacancy,...
Princeton Plasma Physics Laboratory
Not Available
1990-01-01
This report discusses the following topics: principal parameters achieved in experimental devices fiscal year 1990; tokamak fusion test reactor; compact ignition tokamak; Princeton beta experiment- modification; current drive experiment-upgrade; international collaboration; x-ray laser studies; spacecraft glow experiment; plasma processing: deposition and etching of thin films; theoretical studies; tokamak modeling; international thermonuclear experimental reactor; engineering department; project planning and safety office; quality assurance and reliability; technology transfer; administrative operations; PPPL patent invention disclosures for fiscal year 1990; graduate education; plasma physics; graduate education: plasma science and technology; science education program; and Princeton Plasma Physics Laboratory reports fiscal year 1990.
Electrical conductivity of quark matter in magnetic field
B. Kerbikov; M. Andreichikov
2011-12-05
Fermion currents in dense quark matter embedded into magnetic field are under intense discussions motivated by Chiral Magnetic Effect. We argue that conductivity of quark matter may be independent of the magnetic field direction and not proportional to the magnetic field strength.
Quark masses, the Dashen phase, and gauge field topology
Creutz, Michael
2013-12-15
The CP violating Dashen phase in QCD is predicted by chiral perturbation theory to occur when the up–down quark mass difference becomes sufficiently large at fixed down-quark mass. Before reaching this phase, all physical hadronic masses and scattering amplitudes are expected to behave smoothly with the up-quark mass, even as this mass passes through zero. In Euclidean space, the topological susceptibility of the gauge fields is positive at positive quark masses but diverges to negative infinity as the Dashen phase is approached. A zero in this susceptibility provides a tentative signal for the point where the mass of the up quark vanishes. I discuss potential ambiguities with this determination. -- Highlights: •The CP violating Dashen phase in QCD occurs when the up quark mass becomes sufficiently negative. •Before reaching this phase, all physical hadronic masses and scattering amplitudes behave smoothly with the up-quark mass. •The topological susceptibility of the gauge fields diverges to negative infinity as the Dashen phase is approached. •A zero in the topological susceptibility provides a tentative signal for the point where the mass of the up quark vanishes. •The universality of this definition remains unproven. Potential ambiguities are discussed.
The b Quark Fragmentation Function, From LEP to TeVatron
Ben-haim, Eli
2004-12-01
The b quark fragmentation distribution has been measured, using data registered by the DELPHI experiment at the Z pole, in the years 1994-1995. The measurement made use of 176000 inclusively reconstructed B meson candidates. The errors of this measurement are dominated by systematic effects, the principal ones being related to the energy calibration. The distribution has been established in a nine bin histogram. Its mean value has been found to be
$J/?$ and $?_c$ in the Deconfined Plasma from Lattice QCD
M. Asakawa; T. Hatsuda
2003-11-13
Analyzing correlation functions of charmonia at finite temperature ($T$) on $32^3\\times(32-96)$ anisotropic lattices by the maximum entropy method (MEM), we find that $J/\\psi$ and $\\eta_c$ survive as distinct resonances in the plasma even up to $T \\simeq 1.6 T_c$ and that they eventually dissociate between $1.6 T_c$ and $1.9 T_c$ ($T_c$ is the critical temperature of deconfinement). This suggests that the deconfined plasma is non-perturbative enough to hold heavy-quark bound states. The importance of having sufficient number of temporal data points in MEM analyses is also emphasized.
Time evolution of gluon coherent state and its von Neumann entropy in heavy-ion collisions
Hideaki Iida; Teiji Kunihiro; Akira Ohnishi; Toru T. Takahashi
2014-10-27
We propose a new prescription for evaluating a von Neumann entropy in the initial stage of high-energy heavy-ion collisions utilizing the time evolution of classical Yang-Mills (CYM) field: The von Neumann entropy is computed for the quantum coherent states constructed so as to give the classical gluon fields as the expectation values. The entropy is to be liberated when the complete decoherence is achieved. As a demonstration, the time evolution of the CYM dynamics is solved with an initial condition which mimics the Glasma state, though in a non-expanding geometry; the Glasma state is characterized by the longitudinal color-electric and -magnetic fields with gluon fields' fluctuations around it. We find that the initial longitudinal fluctuations of the fields play essential roles for the entropy production in two ways: First, the field fluctuations at $t=0$ themselves act as a source of the von Neumann entropy prepared before the time evolution. Second, the initial fluctuations triggers field instabilities, and hence the larger the strength of them, the more the entropy production at later time.
Inflation of fireballs, the gluon wind and the homogeneity of the HBT radii at RHIC
T. Csorgo; J. Zimanyi
2002-06-20
We solve analytically the ellipsoidally expanding fireball hydrodynamics with source terms in the momentum and the energy equations, using the non-relativistic approximation. We find that energy transport from high pt jets of gluons to the medium leads to a transient, exponential inflation of the fireballs created in high energy heavy ion collisions. In this transient, inflatory period, the slopes of the single particle spectra increase, while the HBT radius parameters decrease exponentially with time. This effect is shown to be similar to the development of the homogeneity of our Universe due to an inflatory period. Independently of the initial conditions, and the exact value of the freeze-out time and temperature, the meausurables (single particle spectra, the correlation functions, the slope parameters, elliptic flow, HBT radii and cross terms) become time independent during the late, non-inflatory stages of the expansion, and they satisfy new kind of scaling laws. If the expansion starts with a transient inflation caused by the gluon wind, it leads naturally to large transverse flows and the simultaneous equality and scaling behaviour of the HBT radius parameters, R_{side} \\approx R_{out} \\approx R_{long} \\approx t_f \\sqrt{T_f/m}. With certain relativistic corrections, the scaling limit is \\tau_f \\sqrt{T_f/m_t}, where m_t is the mean transverse mass of the pair.
Early Time Dynamics of Gluon Fields in High Energy Nuclear Collisions
G. Chen; R. J. Fries; J. I. Kapusta; Y. Li
2015-07-13
Nuclei colliding at very high energy create a strong, quasi-classical gluon field during the initial phase of their interaction. We present an analytic calculation of the initial space-time evolution of this field in the limit of very high energies using a formal recursive solution of the Yang-Mills equations. We provide analytic expressions for the initial chromo-electric and chromo-magnetic fields and for their energy-momentum tensor. In particular, we discuss event-averaged results for energy density and energy flow as well as for longitudinal and transverse pressure of this system. For example, we find that the ratio of longitudinal to transverse pressure very early in the system behaves as $p_L/p_T = -[1-\\frac{3}{2a}(Q\\tau)^2]/[1-\\frac{1}{a}(Q\\tau)^2]+\\mathcal{O}(Q\\tau)^4$ where $\\tau$ is the longitudinal proper time, $Q$ is related to the saturation scales $Q_s$ of the two nuclei, and $a = \\ln (Q^2/\\hat{m}^2)$ with $\\hat m$ a scale to be defined later. Our results are generally applicable if $\\tau \\lesssim 1/Q$. As already discussed in a previous paper, the transverse energy flow $S^i$ of the gluon field exhibits hydrodynamic-like contributions that follow transverse gradients of the energy density $\
Cooling of Neutron Stars with Color Superconducting Quark Cores
David Blaschke; Dmitri N. Voskresensky; Hovik Grigorian
2005-11-03
We show that within a recently developed nonlocal chiral quark model the critical density for a phase transition to color superconducting quark matter under neutron star conditions can be low enough for these phases to occur in compact star configurations with masses below 1.3 M_sun. We study the cooling of these objects in isolation for different values of the gravitational mass and argue that, if the quark matter phase would allow unpaired quarks, the corresponding hybrid stars would cool too fast. The comparison with observational data puts tight constraints on possible color superconducting quark matter phases. Possible candidates with diquark gaps of the order of 10 keV - 1 MeV such as the "2SC+X" and the color spin locking (CSL) phase are presented.
XQCAT: eXtra Quark Combined Analysis Tool
D. Barducci; A. Belyaev; M. Buchkremer; J. Marrouche; S. Moretti; L. Panizzi
2015-09-17
XQCAT (eXtra Quark Combined Analysis Tool) is a tool aimed at determining exclusion confidence levels for scenarios of new physics characterised by the presence of one or multiple heavy extra quarks which interact through Yukawa couplings with any of the Standard Model quarks. The code uses a database of efficiencies for pre-simulated processes of QCD-induced pair production of extra quarks and their subsequent on-shell decays. In the version 1.2 of XQCAT the efficiencies have been computed for a set of seven publicly available search results by the CMS experiment. The input for the code is a text file in which masses, branching ratios and dominant chirality of the couplings of the new quarks are provided. The output of the code is the exclusion confidence levels of the test point for each implemented experimental analysis considered individually and, when possible, in statistical combination.
Physical and cut-off effects of heavy sea quarks
Knechtli, Francesco; Bruno, Mattia; Finkenrath, Jacob; Leder, Björn; Marinkovic, Marina; Sommer, Rainer
2014-01-01
We simulate a theory with two dynamical O($a$) improved Wilson quarks whose mass $M$ ranges from a factor eight up to a factor two below the charm quark mass and at three values of the lattice spacing ranging from 0.066 to 0.034 fm. This theory is a prototype to study the decoupling of heavy quarks. We measure the mass and cut-off dependence of ratios of gluonic observables defined from the Wilson flow or the static potential. The size of the 1/$M$ corrections can be determined and disentangled from the lattice artifacts. The difference with the pure gauge theory is at the percent level when two quarks with a mass of the charm quark are present.
Physical and cut-off effects of heavy sea quarks
Francesco Knechtli; Andreas Athenodorou; Mattia Bruno; Jacob Finkenrath; Björn Leder; Marina Marinkovic; Rainer Sommer
2014-11-05
We simulate a theory with two dynamical O($a$) improved Wilson quarks whose mass $M$ ranges from a factor eight up to a factor two below the charm quark mass and at three values of the lattice spacing ranging from 0.066 to 0.034 fm. This theory is a prototype to study the decoupling of heavy quarks. We measure the mass and cut-off dependence of ratios of gluonic observables defined from the Wilson flow or the static potential. The size of the 1/$M$ corrections can be determined and disentangled from the lattice artifacts. The difference with the pure gauge theory is at the percent level when two quarks with a mass of the charm quark are present.
Ward, P.P.; Dybwad, G.L.
1995-03-01
The Plasma Technology Directory has two main goals: (1) promote, coordinate, and share plasma technology experience and equipment within the Department of Energy; and (2) facilitate technology transfer to the commercial sector where appropriate. Personnel are averaged first by Laboratory and next by technology area. The technology areas are accelerators, cleaning and etching deposition, diagnostics, and modeling.
Triggered plasma opening switch
Mendel, Clifford W. (Albuquerque, NM)
1988-01-01
A triggerable opening switch for a very high voltage and current pulse includes a transmission line extending from a source to a load and having an intermediate switch section including a plasma for conducting electrons between transmission line conductors and a magnetic field for breaking the plasma conduction path and magnetically insulating the electrons when it is desired to open the switch.
Diamagnetism of rotating plasma
Young, W. C.; Hassam, A. B.; Romero-Talamas, C. A.; Ellis, R. F.; Teodorescu, C. [IREAP, University of Maryland, College Park, Maryland 20742 (United States)
2011-11-15
Diamagnetism and magnetic measurements of a supersonically rotating plasma in a shaped magnetic field demonstrate confinement of plasma pressure along the magnetic field resulting from centrifugal force. The Grad-Shafranov equation of ideal magnetohydrodynamic force balance, including supersonic rotation, is solved to confirm that the predicted angular velocity is in agreement with spectroscopic measurements of the Doppler shifts.
From constituent quarks to hadrons in course of nuclear matter expansion
O. D. Chernavskaya; I. I. Royzen
2002-01-13
The up-dated three-phase concept of nuclear matter evolution in course of cooling down - from the phase of quark-qluon plasma (QGP) through the intermediate phase allowing for massive constituent quarks (valons), pions and kaons (QPK) to the phase of hadronic matter (H) - is exploited for the treatment of relative hadronic yields in the central region of heavy ion collisions. The most attention is paid to the description of the QPK-phase which is argued to be a gaseous one and lasts until the valonic spacing approaches the confinement radius (at the temperature about 110 MeV), when the valons start fusing to be locked, in the end, within the hadrons. The hadronic yields emerged from thermal treatment of QPK-phase and simple combinatorial approach to the hadronization process are shown to fit the available experimental data from AGS, SPS and RHIC quite well. This provides an alternative insight into the real origin of the observed relative hadronic yields which is (to a considerable extent) free of the well known puzzle inherent in some conventional models where the early chemical freeze-out is assumed: namely, why the gaseous thermal approach to actually tightly packed (even overlapping) hadrons seems workable? Many predictions for the other hadronic yields which could be observed at these machines as well as at LHC are given.
Search for a heavy vector boson decaying to two gluons in pp? collisions at ?s=1.96??TeV
Gomez-Ceballos, Guillelmo
We present a search for a new heavy vector boson Z[superscript ?] that decays to gluons. Decays to on-shell gluons are suppressed, leading to a dominant decay mode of Z[superscript ?]?g[superscript *]g. We study the case ...
Savage, Mark E. (Albuquerque, NM); Mendel, Jr., Clifford W. (Albuquerque, NM)
2001-01-01
A command triggered plasma opening switch assembly using an amplification stage. The assembly surrounds a coaxial transmission line and has a main plasma opening switch (POS) close to the load and a trigger POS upstream from the main POS. The trigger POS establishes two different current pathways through the assembly depended on whether it has received a trigger current pulse. The initial pathway has both POS's with plasma between their anodes and cathodes to form a short across the transmission line and isolating the load. The final current pathway is formed when the trigger POS receives a trigger current pulse which energizes its fast coil to push the conductive plasma out from between its anode and cathode, allowing the main transmission line current to pass to the fast coil of the main POS, thus pushing its plasma out the way so as to establish a direct current pathway to the load.
Research | Princeton Plasma Physics Lab
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Holographic Screening Length in a Hot Plasma of Two Sphere
Ardian Nata Atmaja; Hasan Abu Kassim; Norhasliza Yusof
2015-04-16
We study the screening length of a quark-antiquark pair moving in a hot plasma living in two sphere $S^2$ manifold using AdS/CFT correspondence where the background metric is four dimensional Schwarzschild-AdS black hole. The geodesic solution of the string ends at the boundary is given by a stationary motion in the equatorial plane as such the separation length $L$ of quark-antiquark pair is parallel to the angular velocity $\\omega$. The screening length and the bound energy are computed numerically using Mathematica. We find that the plots are bounded from below by some functions related to the momentum transfer $P_c$ of the drag force configuration. We compare the result by computing the screening length in the quark-antiquark reference frame where the gravity dual are "Boost-AdS" and Kerr-AdS black holes. Finding relations of the parameters of both black holes, we argue that the relation between mass parameters $M_{Sch}$ of the Schwarzschild-AdS black hole and $M_{Kerr}$ of the Kerr-AdS black hole in high temperature is given by $M_{Kerr}=M_{Sch}(1-a^2l^2)^{3/2}$, where $a$ is the angular momentum parameter.
Duan Chun-Gui; Liu Na
2008-09-28
By means of two typical kinds of quark energy loss parametrization and the nuclear parton distributions determined only with lepton-nuclear deep inelastic scattering experimental data, a leading order analysis are performed on the proton-induced Drell-Yan differential cross section ratios of tungsten versus deuterium as a function of the quark momentum fraction in the beam proton and target nuclei. It is found that the theoretical results with quark energy loss are in good agreement with the experimental data. The quark energy loss effect produce approximately 3% to 11% suppression on the Drell-Yan differential cross section ratios $R_{W/D}$ in the range $0.05\\leq x_2\\leq0.3$. The application of nuclear Drell-Yan data with heavy targets is remarkably subject to difficulty in the constraints of the nuclear sea-quark distribution.
Boundary Plasma Issues in Burning Plasma Science
Pitcher, C. S.
impurity production 4. screening of impurities · why a burning plasma experiment? · BP contribution impurity production, high Zeff (not desirable mode of operation ) #12;···· we know a lot more now than helium ash - induce SOL flow towards divertor - control density · helium exhaust time, i.e. He , limited
Boundary Plasma Issues in Burning Plasma Science
impurity production 4. screening of impurities 5. burning plasma experiment? #12;(1) Wide Dispersal points are swept (BPX), but Tt will be high impurity production, high Zeff (not desirable mode- modes (tight baffling??) · allows efficient pumping to: - remove helium ash - induce SOL flow towards
Boundary Plasma Issues in Burning Plasma Science
Pitcher, C. S.
impurity production 4. screening of impurities 5. burning plasma experiment? #12;(1) Wide Dispersal if strike points are swept (BPX), but Tt will be high impurity production, high Zeff (not desirable mode pressure for H- modes (tight baffling??) · allows efficient pumping to: - remove helium ash - induce SOL
Top Quark Properties in Little Higgs Models
Berger, C.F.; /SLAC; Perelstein, M.; /Cornell U., CIHEP; Petriello, F.; /Wisconsin U., Madison
2005-12-08
Identifying the mechanism which breaks electroweak symmetry and generates fermion masses is one of the main physics goals for both the LHC and the ILC. Studies of the top quark have the potential to illuminate this issue; since it is the heaviest of the Standard Model (SM) fermions, the top is expected to couple strongly to the symmetry-breaking sector. Consequently, the structure of that sector can have significant, potentially observable effects on the properties of the top. for example, it is well known that the vector and axial t{bar t}Z form factors receive large corrections (of order 5-10%) in certain models of dynamical electroweak symmetry breaking [1]. At future colliders such as the LHC and the ILC, we will be able to pursue a program of precision top physics, similar to the program studying the Z at LEP and SLC. In this manuscript, they study the corrections to the top quark properties in ''Little Higgs'' models of electroweak symmetry breaking [2], and compare the expected deviations from the SM predictions with expected sensitivities of experiments at the LHC and the ILC. In the Little Higgs models, electroweak symmetry is driven by the radiative effects from the top sector, including the SM-like top and its heavy counterpart, a TeV-scale ''heavy top'' T. Probing this structure experimentally is quite difficult. While the LHC should be able to discover the T quark, its potential for studying its couplings is limited [3,4]. Direct production of the T will likely be beyond the kinematic reach of the ILC. However, we will show below that the corrections to the gauge couplings of the SM top, induced by its mixing with the T, will be observable at the ILC throughout the parameter range consistent with naturalness. Measuring these corrections will provide a unique window on the top sector of the Little Higgs. Many Little Higgs models have been proposed in the literature. We will consider two examples in this study, the ''Littlest Higgs'' model [5], and its variation incorporating T parity [6].
Chemical and kinetic equilibrations via radiative parton transport
Bin Zhang; Warner A. Wortman
2011-02-21
A hot and dense partonic system can be produced in the early stage of a relativistic heavy ion collision. How it equilibrates is important for the extraction of Quark-Gluon Plasma properties. We study the chemical and kinetic equilibrations of the Quark-Gluon Plasma using a radiative transport model. Thermal and Color-Glass-Condensate motivated initial conditions are used. We observe that screened parton interactions always lead to partial pressure isotropization. Different initial pressure anisotropies result in the same asymptotic evolution. Comparison of evolutions with and without radiative processes shows that chemical equilibration interacts with kinetic equilibration and radiative processes can contribute significantly to pressure isotropization.
Viscosity, wave damping and shock wave formation in cold hadronic matter
D. A. Fogaça; F. S. Navarra; L. G. Ferreira Filho
2013-09-06
We study linear and nonlinear wave propagation in a dense and cold hadron gas and also in a cold quark gluon plasma, taking viscosity into account and using the Navier-Stokes equation. The equation of state of the hadronic phase is derived from the nonlinear Walecka model in the mean field approximation. The quark gluon plasma phase is described by the MIT equation of state. We show that in a hadron gas viscosity strongly damps wave propagation and also hinders shock wave formation. This marked difference between the two phases may have phenomenological consequences and lead to new QGP signatures.
Herman, H.
1988-09-01
Plasma spraying is one way to apply protective coatings. The hot, high-speed flame of a plasma gun can melt a powder of almost any ceramic or metal and spray it to form a coating for protection against corrosion, wear or high temperature. The technique carries much less risk of degrading the coating and substrate than many other high-temperature processes do, because the gas in the plasma flame is chemically inert and the target can be kept fairly cool. And yet a plasma gun can be only a little more cumbersome than a paint sprayer. Investigators are applying this technique to new materials. The General Electric Company is using vacuum plasma spraying to make freestanding components: intricate aircraft engine parts formed by plasma-spraying a superalloy on a removable substrate. Other workers spray ceramic particles or fibers and metal powder simulatious wrong, stiff composite materials: the ceramic particles dispersed in a matrix of metal. The author and colleagues at the U.S. Naval Research Laboratory have fabricated a thick film of high-temperature superconductor by plasma-spraying the compound in the form of a powder. 7 figs.
Wilson flow with naive staggered quarks
Saumen Datta; Sourendu Gupta; Anirban Lahiri; Andrew Lytle; Pushan Majumdar
2015-07-03
Scale setting for QCD with two flavours of staggered quarks is examined using Wilson flow over a factor of four change in both the lattice spacing and the pion mass. The statistics needed to keep the errors in the flow scale fixed is found to increase approximately as the inverse square of the lattice spacing. Tree level improvement of the scales t_0 and w_0 is found to be useful in most of the range of lattice spacings we explore. The scale uncertainty due to remaining lattice spacing effects is found to be about 3%. The ratio w_0/\\sqrt{t_0} is N_f dependent and we find its continuum limit to be 1.106 \\pm 0.007 (stat) \\pm 0.005 (syst) for m_\\pi w_0 \\simeq 0.3.
Top Quark Production Measurements at ATLAS
Robert Calkins; for the ATLAS Collaboration
2011-10-05
An overview of top quark production measurements using the ATLAS detector at the LHC is presented. Using 35 pb^-1 of data, we measured the ttbar cross-section in the lepton+jets channel to 13% precision and set limits on the cross-section for the all hadronic decay channel. The measurement in the dilepton channel was performed using 0.70 fb^-1 of data and was combined with the lepton+jets channel result for our most precise ttbar cross-section measurement of \\sigma(ttbar+X) =176 +- 5(stat) +13 -10 (syst) +-7(lumi). Single top production was also measured in the t-channel using 0.70 fb^-1 of data.
Heavy Quark Production at the Tevatron
Sally Seidel
2008-08-25
Results are presented from four CDF analyses involving heavy quark production in proton-antiproton collisions at center of mass energy 1.96 TeV. The shapes of b-jets are found to be broader than inclusive predictions and broader than both PYTHIA and HERWIG defaults. A measurement of the production cross section for psi(2S) is consistent with Run 1 results and with theoretical predictions associated with parton distribution function energy dependence. The inclusive b-jet production cross section is also consistent with theoretical predictions over six orders of magnitude. The b-bbar differential production cross section is compared to several theoretical models and found to be best described by MC@NLO + JIMMY.
Combined search for the quarks of a sequential fourth generation
CMS Collaboration
2013-03-13
Results are presented from a search for a fourth generation of quarks produced singly or in pairs in a data set corresponding to an integrated luminosity of 5 inverse femtobarns recorded by the CMS experiment at the LHC in 2011. A novel strategy has been developed for a combined search for quarks of the up and down type in decay channels with at least one isolated muon or electron. Limits on the mass of the fourth-generation quarks and the relevant Cabibbo-Kobayashi-Maskawa matrix elements are derived in the context of a simple extension of the standard model with a sequential fourth generation of fermions. The existence of mass-degenerate fourth-generation quarks with masses below 685 GeV is excluded at 95% confidence level for minimal off-diagonal mixing between the third- and the fourth-generation quarks. With a mass difference of 25 GeV between the quark masses, the obtained limit on the masses of the fourth-generation quarks shifts by about +/- 20 GeV. These results significantly reduce the allowed parameter space for a fourth generation of fermions.
Optical plasma microelectronic devices
Forati, Ebrahim; Dill, Thyler; Sievenpiper, Dan
2015-01-01
The semiconductor channel in conventional microelectronic devices was successfully replaced with an optically triggered gas plasma channel. The combination of DC and laser-induced gas ionizations controls the conductivity of the channel, enabling us to realize different electronic devices such as transistors, switches, modulators, etc. A special micro-scale metasurface was used to enhance the laser-gas interaction, as well as combining it with DC ionization properly. Optical plasma devices benefit form the advantages of plasma/vacuum electronic devices while preserving most of the integrablity of semiconductor based devices.
Top quark production and properties at the Tevatron
Fiedler, Frank; /Munich U.
2005-06-01
The precise measurement of top quark production and properties is one of the primary goals of the Tevatron during Run II. The total t{bar t} production cross-section has been measured in a large variety of decay channels and using different selection criteria. Results from differential cross-section measurements and searches for new physics in t{bar t} production and top quark decays are available. Electroweak production of single top quarks has been searched for. The results from all these analyses, using typically 200 pb{sup -1} of data, are presented.
Hybrid stars within a covariant, nonlocal chiral quark model
D. B. Blaschke; D. Gomez Dumm; A. G. Grunfeld; T. Klahn; N. N. Scoccola
2007-05-16
We present a hybrid equation of state (EoS) for dense matter in which a nuclear matter phase is described within the Dirac-Brueckner-Hartree-Fock (DBHF) approach and a two-flavor quark matter phase is modelled according to a recently developed covariant, nonlocal chiral quark model. We show that modern observational constraints for compact star masses (M ~ 2 M_sun) can be satisfied when a small vector-like four quark interaction is taken into account. The corresponding isospin symmetric EoS is consistent with flow data analyses of heavy ion collisions and points to a deconfinement transition at about 0.55 fm^-3.
Heavy-baryon quark model picture from lattice QCD
J. Vijande; A. Valcarce; H. Garcilazo
2015-07-14
The ground state and excited spectra of baryons containing three identical heavy quarks, $b$ or $c$, have been recently calculated in nonperturbative lattice QCD. The energy of positive and negative parity excitations has been determined with high precision. Lattice results constitute a unique opportunity to learn about the quark-confinement mechanism as well as elucidating our knowledge about the nature of the strong force. We analyze the nonperturbative lattice QCD results by means of heavy-quark static potentials derived using SU(3) lattice QCD. We make use of different numerical techniques for the three-body problem.
Golden Bars of Consensus and the Truth Quark
Frank D. Tony Smith; jr
2002-05-14
Scientists are imprisoned by Golden Bars of Consensus, says Burton Richter (hep-ex/0001012). A case in point is the mass of the Truth Quark. The consensus analysis of the experimental data indicates that the mass of the Truth Quark is about 170 GeV. On the other hand, an alternative analysis of the same data indicates that the mass of the Truth Quark is about 130 GeV. If the design of future experiments, including trigger, event selection, data analysis procedures, error analysis, etc., takes into account only the consensus value, and if the consensus value happens to be incorrect, then results of future experiments might be compromised.
Calculation of the strange quark mass using domain wall fermions
Tom Blum; Amarjit Soni; Matthew Wingate
2000-09-18
We present a first calculation of the strange quark mass using domain wall fermions. This paper contains an overview of the domain wall discretization and a pedagogical presentation of the perturbative calculation necessary for computing the mass renormalization. We combine the latter with numerical simulations to estimate the strange quark mass. Our final result in the quenched approximation is 95(26) MeV in the ${\\bar{MS}}$ scheme at a scale of 2 GeV. We find that domain wall fermions have a small perturbative mass renormalization, similar to Wilson quarks, and exhibit good scaling behavior.
Strange quark mass and Lambda parameter by the ALPHA collaboration
Marinkovic, Marina; Sommer, Rainer; Virotta, Francesco
2011-01-01
We determine f_K for lattice QCD in the two flavor approximation with non-perturbatively improved Wilson fermions. The result is used to set the scale for dimensionful quantities in CLS/ALPHA simulations. To control its dependence on the light quark mass, two different strategies for the chiral extrapolation are applied. Combining f_K and the bare strange quark mass with non-perturbative renormalization factors and step scaling functions computed in the Schroedinger Functional, we determine the RGI strange quark mass and the Lambda parameter in units of f_K.
Strange quark mass and Lambda parameter by the ALPHA collaboration
Marina Marinkovic; Stefan Schaefer; Rainer Sommer; Francesco Virotta
2011-12-18
We determine f_K for lattice QCD in the two flavor approximation with non-perturbatively improved Wilson fermions. The result is used to set the scale for dimensionful quantities in CLS/ALPHA simulations. To control its dependence on the light quark mass, two different strategies for the chiral extrapolation are applied. Combining f_K and the bare strange quark mass with non-perturbative renormalization factors and step scaling functions computed in the Schroedinger Functional, we determine the RGI strange quark mass and the Lambda parameter in units of f_K.
PRINCETON PLASMA PHYSICS LABORATORY PPPL UC Davis PRINCETON PLASMA PHYSICS LABORATORY PPPL UC Davis Scattering System for ETG physics on NSTX H. Park, E. Mazzucato, and D. Smith PPPL, Princeton University C, 2006 Hyatt Regency, Dallas, TX #12;PRINCETON PLASMA PHYSICS LABORATORY PPPL UC Davis PRINCETON PLASMA
Running coupling constant from lattice studies of gluon and ghost propagators
Cucchieri, A.; Mendes, T.
2004-12-02
We present a numerical study of the running coupling constant in four-dimensional pure-SU(2) lattice gauge theory. The running coupling is evaluated by fitting data for the gluon and ghost propagators in minimal Landau gauge. Following Refs. [1, 2], the fitting formulae are obtained by a simultaneous integration of the {beta} function and of a function coinciding with the anomalous dimension of the propagator in the momentum subtraction scheme. We consider these formulae at three and four loops. The fitting method works well, especially for the ghost case, for which statistical error and hyper-cubic effects are very small. Our present result for {lambda}MS is 200{sub -40}{sup +60} MeV, where the error is purely systematic. We are currently extending this analysis to five loops in order to reduce this systematic error.
Free Energy and Plaquette expectation value for gluons on the lattice, in three dimensions
H. Panagopoulos; A. Skouroupathis; A. Tsapalis
2006-02-24
We calculate the perturbative value of the Free Energy in Lattice QCD in three dimensions, up to three loops. Our calculation is performed using the Wilson formulation for gluons in SU(N) gauge theories. The Free Energy is directly related to the average plaquette. To carry out the calculation, we compute the coefficients involved in the perturbative expansion of the Free Energy up to three loops, using an automated set of procedures developed by us in Mathematica. The dependence on N is shown explicitly in our results. For purposes of comparison, we also present the individual contributions from every diagram. These have been obtained by means of two independent calculations, in order to cross check our results.
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processes. A typical configuration uses a low intensity laser beam (2nd, 3rd, or 4th harmonic of 1054-nm) to probe a plasma volume. The Thomson scattered light is collected by a...
Accelerating Particles with Plasma
Litos, Michael; Hogan, Mark
2014-11-05
Researchers at SLAC explain how they use plasma wakefields to accelerate bunches of electrons to very high energies over only a short distance. Their experiments offer a possible path for the future of particle accelerators.
Holland, Chris [UC San Diego, San Diego, California, United States
2010-01-08
The upcoming ITER experiment (www.iter.org) represents the next major milestone in realizing the promise of using nuclear fusion as a commercial energy source, by moving into the ?burning plasma? regime where the dominant heat source is the internal fusion reactions. As part of its support for the ITER mission, the US fusion community is actively developing validated predictive models of the behavior of magnetically confined plasmas. In this talk, I will describe how the plasma community is using the latest high performance computing facilities to develop and refine our models of the nonlinear, multiscale plasma dynamics, and how recent advances in experimental diagnostics are allowing us to directly test and validate these models at an unprecedented level.
Plasma isotope separation methods
Grossman, M.W. ); Shepp, T.A. )
1991-12-01
Isotope separation has many important industrial, medical, and research applications. Large-scale processes have typically utilized complex cascade systems; for example, the gas centrifuge. Alternatively, high single-stage enrichment processes (as in the case of the calutron) are very energy intensive. Plasma-based methods being developed for the past 15 to 20 years have attempted to overcome these two drawbacks. In this review, six major types of isotope separation methods which involve plasma phenomena are discussed. These methods are: plasma centrifuge, AVLIS (atomic vapor laser isotope separation), ion wave, ICR (ion-cyclotron resonance), calutron, and gas discharge. The emphasis of this paper is to describe the plasma phenomena in these major categories. An attempt was made to include enough references so that more detailed study or evaluation of a particular method could readily be pursued. A brief discussion of isotope separation using mass balance concepts is also carried out.
Eakle, Robert F. (New Ellenton, SC); Pak, Donald J. (Martine, GA)
2004-10-26
A mounting system for a flat display screen, particularly a plasma display screen, suspends the screen separately in each of the x-, y- and z-directions. A series of frames located by linear bearings and isolated by springs and dampers allows separate controlled movement in each axis. The system enables the use of relatively larger display screens in vehicles in which plasma screen are subject to damage from vibration.
Electrostatics of moving plasma
Ignatov, A. M.
2013-07-15
The stability of charge distribution over the surface of a conducting body in moving plasma is analyzed. Using a finite-width plate streamlined by a cold neutralized electron flow as an example, it is shown that an electrically neutral body can be unstable against the development of spontaneous polarization. The plasma parameters at which such instability takes place, as well as the frequency and growth rate of the fundamental mode of instability, are determined.
Dynamical quark loop light-by-light contribution to muon g-2 within the nonlocal chiral quark model
A. E. Dorokhov; A. E. Radzhabov; A. S. Zhevlakov
2015-07-24
The hadronic corrections to the muon anomalous magnetic moment a_mu, due to the gauge-invariant set of diagrams with dynamical quark loop light-by-light scattering insertions, are calculated in the framework of the nonlocal chiral quark model. These results complete calculations of all hadronic light-by-light scattering contributions to a_mu in the leading order in the 1/Nc expansion. The result for the quark loop contribution is a_mu^{HLbL,Loop}=(11.0+-0.9)*10^(-10), and the total result is a_mu^{HLbL,NxQM}=(16.8+-1.2)*10^(-10).
Moving Quarks Help Solve Proton Spin Puzzle | Jefferson Lab
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Moving Quarks Help Solve Proton Spin Puzzle NEWPORT NEWS, VA., Sept. 11, 2008 - New theory work at the U.S. Department of Energy's Thomas Jefferson National Accelerator Facility...
Precision Top-Quark Mass Measurement at CDF
Gomez-Ceballos, Guillelmo
We present a precision measurement of the top-quark mass using the full sample of Tevatron ?s=1.96??TeV proton-antiproton collisions collected by the CDF II detector, corresponding to an integrated luminosity of ...
Modelling Hybrid Stars in Quark-Hadron Approaches
Schramm, S; Negreiros, R
2015-01-01
The density in the core of neutron stars can reach values of about 5 to 10 times nuclear matter saturation density. It is, therefore, a natural assumption that hadrons may have dissolved into quarks under such conditions, forming a hybrid star. This star will have an outer region of hadronic matter and a core of quark matter or even a mixed state of hadrons and quarks. In order to investigate such phases, we discuss different model approaches that can be used in the study of compact stars as well as being applicable to a wider range of temperatures and densities. One major model ingredient, the role of quark interactions in the stability of massive hybrid stars is discussed. In this context, possible conflicts with lattice QCD simulations are investigated.
Instantons and quark zero modes in AdS/QCD
Jacopo Bechi
2009-09-16
In this paper the quark zero modes creation effect is studied in the context of the AdS/QCD approach. This effect is generated, in presence of instantons, by a new that can be added in the bulk.
Modelling Hybrid Stars in Quark-Hadron Approaches
S. Schramm; V. Dexheimer; R. Negreiros
2015-08-18
The density in the core of neutron stars can reach values of about 5 to 10 times nuclear matter saturation density. It is, therefore, a natural assumption that hadrons may have dissolved into quarks under such conditions, forming a hybrid star. This star will have an outer region of hadronic matter and a core of quark matter or even a mixed state of hadrons and quarks. In order to investigate such phases, we discuss different model approaches that can be used in the study of compact stars as well as being applicable to a wider range of temperatures and densities. One major model ingredient, the role of quark interactions in the stability of massive hybrid stars is discussed. In this context, possible conflicts with lattice QCD simulations are investigated.
Color superconductivity with determinant interaction in strange quark matter
Amruta Mishra; Hiranmaya Mishra
2006-08-28
We investigate the effect of six fermion determinant interaction on color superconductivity as well as on chiral symmetry breaking. Coupled mass gap equations and the superconducting gap equation are derived through the minimisation of the thermodynamic potential. The effect of nonzero quark -- antiquark condensates on the superconducting gap is derived. This becomes particularly relevant for the case of 2-flavor superconducting matter with unpaired strange quarks in the diquark channel. While the effect of six fermion interaction leads to an enhancement of u-d superconductivity, due to nonvanishing strange quark--antiquark condensates, such an enhancement will be absent at higher densities for u-s or d-s superconductivity due to early (almost) vanishing of light quark-- antiquark condensates.
Fermilab | Newsroom | Press Releases | September 27, 2012: QuarkNet...
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RELEASE QuarkNet program receives 6.1 million NSF award to advance science education Hi-res | Med-res Steven Grosland, physics teacher at Glenbrook South High School in...
Kaon semileptonic decay form factors with HISQ valence quarks
E. Gamiz; J. A. Bailey; A. Bazavov; C. Bernard; C. Bouchard; C. DeTar; D. Du; A. X. El-Khadra; J. Foley; E. D. Freeland; Steven Gottlieb; U. M. Heller; J. Kim; A. S. Kronfeld; J. Laiho; L. Levkova; P. B. Mackenzie; E. T. Neil; M. B. Oktay; Si-Wei Qiu; J. N. Simone; R. Sugar; D. Toussaint; R. S. Van de Water; R. Zhou
2012-11-05
We report on the status of our kaon semileptonic form factor calculations using the highly-improved staggered quark (HISQ) formulation to simulate the valence fermions. We present results for the form factor f_+^{K \\pi}(0) on the asqtad N_f=2+1 MILC configurations, discuss the chiral-continuum extrapolation, and give a preliminary estimate of the total error. We also present a more preliminary set of results for the same form factor but with the sea quarks also simulated with the HISQ action; these results include data at the physical light quark masses. The improvements that we expect to achieve with the use of the HISQ configurations and simulations at the physical quark masses are briefly discussed.
Now Playing change Listen Live Search Quirks & Quarks
Whitney, David
of recent interviews with science authors. podcasts facebook twitter rss Stay Connected with Quirks & Quarks of an actual dinosaur, he used an actual elephant to do his experiment. What he found was that it made little
Yield and suppression of electrons from open heavy-flavor decays in heavy-ion collisions
Anders Knospe
2011-12-31
Measurements by the STAR and PHENIX collaborations indicate that a quark-gluon plasma, a hot and dense state of matter in which quarks and gluons are not confined inside hadrons, is formed in heavy-ion collisions at the Relativistic Heavy Ion Collider. Charm and bottom quarks have been predicted to interact with the medium differently than the light quarks; a study of heavy quark interactions with the medium provides an important test of theoretical models of the quark-gluon plasma. The spectrum of non-photonic electrons (and positrons) is dominated by electrons from the semileptonic decays of D and B mesons. Therefore, non-photonic electrons serve as proxies for heavy quarks. A measurement of the modification of the non-photonic electron spectrum in nucleus-nucleus collisions relative to p + p collisions allows the interactions of heavy quarks with the medium to be studied. Previous measurements indicate that high-transverse-momentum non-photonic electrons are suppressed in Au + Au collisions at 200 GeV (center-of-mass energy per nucleon pair) relative to p + p collisions at the same energy. The magnitude of that suppression is larger than was anticipated and it has been a challenge for theoretical models to predict the in-medium energy loss of light and heavy quarks simultaneously. This dissertation presents the first measurement of the yield of non-photonic electrons from open heavy-flavor decays in Cu + Cu collisions at 200 GeV and the suppression of that yield relative to p + p collisions. A comparison of this result to similar results for Au + Au collisions provides some indication that the geometry of a heavy-ion collision affects the average amount of energy loss by heavy quarks passing through the quark-gluon plasma.
Apyan, Aram
A search for a standard model Higgs boson produced in association with a top-quark pair and decaying to bottom quarks is presented. Events with hadronic jets and one or two oppositely charged leptons are selected from a ...
Searching for the fourth family quarks through anomalous decays
Sahin, M.; Sultansoy, S.; Turkoz, S. [TOBB University of Economics and Technology, Physics Division, Ankara (Turkey); TOBB University of Economics and Technology, Physics Division, Ankara, Turkey and Institute of Physics, National Academy of Sciences, Baku (Azerbaijan); Ankara University, Department of Physics, Ankara (Turkey)
2010-09-01
The flavor democracy hypothesis predicts the existence of the fourth standard model family. Because of the high masses of the fourth family quarks, their anomalous decays could be dominant if certain criteria are met. This will drastically change the search strategy at hadron colliders. We show that the fourth standard model family down quarks with masses up to 400-450 GeV can be observed (or excluded) via anomalous decays by Tevatron.
Reconstructing top quark-antiquark events with one lost jet
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Demina, Regina [Univ. of Rochester, Rochester, NY (United States); Harel, Amnon [Univ. of Rochester, Rochester, NY (United States); Orbaker, Douglas [Univ. of Rochester, Rochester, NY (United States)
2015-07-01
We present a technique for reconstructing the kinematics of pair-produced top quarks that decay to a charged lepton, a neutrino and four final state quarks in the subset of events where only three jets are reconstructed. We present a figure of merit that allows for a fair comparison of reconstruction algorithms without requiring their calibration. The new reconstruction of events with only three jets is fully competitive with the full reconstruction typically used for four-jet events.