Gamma ray signal from gravitationally boosted neutralinos at the galactic center

Neutralinos may be gravitationally boosted near the super-massive black hole at the galactic center so that they can have enough collision energy to annihilate into a stau pair. Since in some phenomenologically favored supersymmetric models the mass splitting between the neutralino and the lightest stau is a few GeVs, this channel may be allowed. In addition, staus can only decay into a tau lepton and another neutralino. We discuss the mechanisms behind this phenomenon and the gamma-ray spectrum and flux generated by the tau pair.