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Title: Dark Matter Coannihilation with a Lighter Species

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Journal Article: Publisher's Accepted Manuscript
Journal Name:
Physical Review Letters
Additional Journal Information:
Journal Volume: 119; Journal Issue: 12; Related Information: CHORUS Timestamp: 2017-09-19 10:37:37; Journal ID: ISSN 0031-9007
American Physical Society
Country of Publication:
United States

Citation Formats

Berlin, Asher. Dark Matter Coannihilation with a Lighter Species. United States: N. p., 2017. Web. doi:10.1103/PhysRevLett.119.121801.
Berlin, Asher. Dark Matter Coannihilation with a Lighter Species. United States. doi:10.1103/PhysRevLett.119.121801.
Berlin, Asher. 2017. "Dark Matter Coannihilation with a Lighter Species". United States. doi:10.1103/PhysRevLett.119.121801.
title = {Dark Matter Coannihilation with a Lighter Species},
author = {Berlin, Asher},
abstractNote = {},
doi = {10.1103/PhysRevLett.119.121801},
journal = {Physical Review Letters},
number = 12,
volume = 119,
place = {United States},
year = 2017,
month = 9

Journal Article:
Free Publicly Available Full Text
This content will become publicly available on September 19, 2018
Publisher's Accepted Manuscript

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  • High-energy neutrinos may resonate with relic background neutralinos to form short-lived sneutrinos. In some circumstances, the decay chain that leads back to the lightest supersymmetric particle would yield few-GeV gamma rays or charged-particle signals. Although resonant coannihilation would occur at an appreciable rate in our galaxy, the signal in any foreseeable detector is unobservably small.
  • In this paper, we introduce a novel program of fixed-target searches for thermal-origin Dark Matter (DM), which couples inelastically to the Standard Model. Since the DM only interacts by transitioning to a heavier state, freeze-out proceeds via coannihilation and the unstable heavier state is depleted at later times. For sufficiently large mass splittings, direct detection is kinematically forbidden and indirect detection is impossible, so this scenario can only be tested with accelerators. Here we propose new searches at proton and electron beam fixed-target experiments to probe sub-GeV coannihilation, exploiting the distinctive signals of up- and down-scattering as well as decaymore » of the excited state inside the detector volume. We focus on a representative model in which DM is a pseudo-Dirac fermion coupled to a hidden gauge field (dark photon), which kinetically mixes with the visible photon. We define theoretical targets in this framework and determine the existing bounds by reanalyzing results from previous experiments. We find that LSND, E137, and BaBar data already place strong constraints on the parameter space consistent with a thermal freeze-out origin, and that future searches at Belle II and MiniBooNE, as well as recently-proposed fixed-target experiments such as LDMX and BDX, can cover nearly all remaining gaps. We also briefly comment on the discovery potential for proposed beam dump and neutrino experiments which operate at much higher beam energies.« less
  • In universal extra dimension models, the lightest Kaluza-Klein (KK) particle is generically the first KK excitation of the photon and can be stable, serving as particle dark matter. We calculate the thermal relic abundance of the KK photon for a general mass spectrum of KK excitations including full coannihilation effects with all (level-one) KK excitations. We find that including coannihilation can significantly change the relic abundance when the coannihilating particles are within about 20% of the mass of the KK photon. Matching the relic abundance with cosmological data, we find the mass range of the KK photon is much widermore » than previously found, up to about 2 TeV if the masses of the strongly interacting level-one KK particles are within 5% of the mass of the KK photon. We also find cases where several coannihilation channels compete (constructively and destructively) with one another. The lower bound on the KK photon mass, about 540 GeV when just right-handed KK leptons coannihilate with the KK photon, relaxes upward by several hundred GeV when coannihilation with electroweak KK gauge bosons of the same mass is included.« less
  • We examine the stau-neutralino coannihilation (CA) mechanism of the early Universe. We use the minimal supergravity (mSUGRA) model and show that from measurements at the CERN Large Hadron Collider one can predict the dark matter relic density with an uncertainty of 6% with 30 fb{sup -1} of data, which is comparable to the direct measurement by the Wilkinson Microwave Anisotropy Probe. This is done by measuring four mSUGRA parameters m{sub 0}, m{sub 1/2}, A{sub 0}, and tan{beta} without requiring direct measurements of the top squark and bottom squark masses. We also provide precision measurements of the gaugino, squark, and lightermore » stau masses in this CA region without assuming gaugino universality.« less