Protohalo Constraints to the Resonant Annihilation of Dark Matter

Abstract

It has recently been argued that the PAMELA, ATIC and PPB-BETS data showing an anomalous excess of high-energy cosmic ray positrons and electrons might be explained by dark matter annihilating in the Galactic halo with a cross section resonantly enhanced compared to its value in the primeval plasma. We find that with a very large annihilation cross section the flash of energetic photons and electron-positron pairs expected from dark-matter annihilation in the first protohalos that form at redshift z~40 is likely substantial and observable. As a consequence, bounds on the allowed energy injection into the primordial gas and the energy density of the diffuse gamma-ray background give rise to limits on the low-velocity dark matter cross section that can be difficult to reconcile with this interpretation of the PAMELA, ATIC and PPB-BETS results.

5 pages, 4 figures; References added, estimates refined and discussion extended

References in corpus (9)

• Observation of an anomalous positron abundance in the cosmic radiation
• A Theory of Dark Matter
• Measurement of the Cosmic Ray e+ plus e- spectrum from 20 GeV to 1 TeV with the Fermi Large Area Telescope
• What mass are the smallest protohalos?
• PAMELA Positron Excess as a Signal from the Hidden Sector
• Contraints on radiative dark-matter decay from the cosmic microwave background
• Dark Matter Signals from Cascade Annihilations
• Galactic Substructure and Direct Detection of Dark Matter
• Extragalactic Inverse Compton Light from Dark Matter Annihilation and the Pamela Positron Excess

Cited by in corpus (2)

• Strong Optimized Conservative Fermi-LAT Constraints on Dark Matter Models from the Inclusive Photon Spectrum
• Higgsino dark matter model consistent with galactic cosmic ray data and possibility of discovery at LHC-7