1205.2688 (James M. Cline)
James M. Cline
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 containing a charged component, 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 should be a doublet under SU(2) to satisfy precision electroweak constraints, and colored under a hidden sector SU(N) or QCD to confine the charged relic S^+. We need lambda_X ~ 3 and m_S ~ m_X to get a large enough XX -> gamma Z 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-pions, which will be pair-produced in colliders and then decay predominantly to XX, hh (or hadronic jets) and subdominantly to gamma gamma. The cross section for X on nucleons is in marginal conflict with the Xenon100 upper limit, suggesting that it should be discovered soon by direct detection.
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http://arxiv.org/abs/1205.2688
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