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Searches for Dark Matter.

By Daniel James Phalen

Abstract

We examine indirect detection for neutralino dark matter. After a brief review of cosmic ray propagation, we discuss signals for positrons, antiprotons, synchrotron radiation and gamma rays from wino annihilation in the galactic halo. The PAMELA data may admit an interpretation as a signal from a wino-like LSP of mass about 200 GeV, normalized to the local relic density, and annihilating mainly into W-bosons. This possibility requires the current conventional estimate for the energy loss rate of positrons be too large by roughly a factor of five. Data from anti-protons and gamma rays also provide tension with this interpretation, but there are significant astrophysical uncertainties associated with each. Forthcoming PAMELA and Fermi data should provide important clues as to whether this scenario is correct. We then go on to propose a scenario that favors production of positrons over antiprotons. Dark matter annihilates through channels involving a new heavy vectorlike lepton which then decays by mixing with Standard Model leptons. If charged, this heavy lepton might be produced at the LHC, and could lead to multi-lepton final states or to long-lived charged tracks. Large neutrino detectors such as ANTARES or IceCube might be sensitive to a monochromatic neutrino line. We study the correlation between spin-independent and spin-dependent scattering in the context of MSSM neutralino dark matter for both thermal and non-thermal histories. We explore the generality of this relationship with reference to other models. We discuss why either fine-tuning or numerical coincidences are necessary for the correlation to break down. We derive upper bounds on spin-dependent scattering mediated by a Z boson. Finally, for convincing dark matter indirect detection, astrophysical backgrounds would need to be disentangled to determine the dark matter contribution to cosmic ray signals. We show that synchrotron emission from electron-positron pairs injected into the interstellar medium by the galactic population of pulsars with energies in the 1 to 100 GeV range can explain the WMAP haze. The same spectrum of high energy electron-positron pairs from pulsars, which gives rise to the haze, may also generate the observed excesses in PAMELA

Topics: Dark Matter
OAI identifier: oai:deepblue.lib.umich.edu:2027.42/75950
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