Explosive Dark Matter Annihilation

Abstract

If the Dark Matter (DM) in the Universe has interactions with the standard-model particle, the pair annihilation may give the imprints in the cosmic ray. In this paper we study the pair annihilation processes of the DM, which is neutral, however has the electroweak (EW) gauge non-singlet. In this estimation the non-relativistic (NR) effective theory in the EW sector is a suitable technique. We find that if the DM mass is larger than about 1 TeV, the attractive Yukawa potentials induced by the EW gauge bosons have significant effects on the DM annihilation processes, and the cross sections may be enhanced by several orders of magnitude, due to the zero energy resonance under the potentials. Especially, the annihilation to two $γ$'s might have a comparable cross section to other tree-level processes, while the cross section under the conventional calculation is suppressed by a loop factor. We also discuss future sensitivities to the $γ$ ray from the galactic center by the GLAST satellite detector and the Air Cerenkov Telescope (ACT) arrays.