130 GeV dark matter and the Fermi gamma-ray line

Abstract

Based on tentative evidence for a peak in the Fermi gamma-ray spectrum originating from near the center of the galaxy, it has been suggested that dark matter of mass ~130 GeV is annihilating directly into photons with a cross section ~24 times smaller than that needed for the thermal relic density. We propose a simple particle physics model in which the DM is a scalar X, with a coupling lambda_X X^2|S|^2 to a scalar multiplet S carrying electric charge, which allows for XX -> gamma gamma at one loop due to the virtual S. We predict a second monochromatic photon peak at 114 GeV due to XX-> gamma Z. The S is colored under a hidden sector SU(N) or QCD to help boost the XX -> gamma gamma cross section. The analogous coupling lambda_h h^2 |S|^2 to the Higgs boson can naturally increase the partial width for h -> gamma gamma by an amount comparable to its standard model value, as suggested by recent measurements from CMS. Due to the hidden sector SU(N) (or QCD), S binds to its antiparticle to form S-mesons, which will be pair-produced in colliders and then decay predominantly to XX, hh, or to glueballs of the SU(N) which subsequently decay to photons. The cross section for X on nucleons is close to the Xenon100 upper limit, suggesting that it should be discovered soon by direct detection.