Interpretation of the Galactic Center excess of gamma rays with heavier dark matter particles

Abstract

Previous attempts at explaining the gamma-ray excess near the Galactic Center have focused on dark matter annihilating directly into Standard Model particles. This results in a preferred dark matter mass of 30--40 GeV (if the annihilation is into $b$ quarks) or 10 GeV (if it is into leptons). Here we show that the gamma-ray excess is also consistent with heavier dark matter particles; in models of secluded dark matter, dark matter with mass up to 76 GeV provides a good fit to the data. This occurs if the dark matter first annihilates to an on-shell particle that subsequently decays to Standard Model particles through a portal interaction. This is a generic process that works in models with annihilation, semi-annihilation or both. We explicitly demonstrate this in a model of hidden vector dark matter with an SU(2) gauge group in the hidden sector.