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arXiv · 1504.05187

Monochromatic Gamma Rays from Dark Matter Annihilation to Leptons

Adam Coogan·Stefano Profumo·William Shepherd
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Abstract

We investigate the relation between the annihilation of dark matter (DM) particles into lepton pairs and into 2-body final states including one or two photons. We parametrize the DM interactions with leptons in terms of contact interactions, and calculate the loop-level annihilation into monochromatic gamma rays, specifically computing the ratio of the DM annihilation cross sections into two gamma rays versus lepton pairs. While the loop-level processes are generically suppressed in comparison with the tree-level annihilation into leptons, we find that some choices for the mediator spin and coupling structure lead to large branching fractions into gamma-ray lines. This result has implications for a dark matter contribution to the AMS-02 positron excess. We also explore the possibility of mediators which are charged under a dark symmetry and find that, for these loop-level processes, an effective field theory description is accurate for DM masses up to about half the mediator mass.

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Adam Coogan, Stefano Profumo, William Shepherd. 2015-04-20. Monochromatic Gamma Rays from Dark Matter Annihilation to Leptons. https://doi.org/10.1007/jhep08(2015)074

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