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Evidence for an excess of gamma rays with O(GeV) energy coming from thecenter of our galaxy has been steadily accumulating over the past severalyears. Recent studies of the excess in data from the Fermi telescope have castdoubt on an explanation for the excess arising from unknown astrophysicalsources. A potential source of the excess is the annihilation of dark matterinto standard model final states, giving rise to gamma ray production. Thespectrum of the excess is well fit by 30 GeV dark matter annihilating into apair of b quarks with a cross section of the same order of magnitude asexpected for a thermal relic. Simple models that can lead to this annihilationchannel for dark matter are in strong tension with null results from directdetection experiments. We construct a renormalizable model where darkmatter-standard model interactions are mediated by a pseudoscalar that mixeswith the CP-odd component of a pair of Higgs doublets, allowing for the gammaray excess to be explained while suppressing the direct detection signal. Weconsider implications for this scenario from Higgs decays, rare B meson decaysand monojet searches and also comment on some difficulties that any dark mattermodel explaining the gamma ray excess via direct annihilation into quarks willencounter.

A Renormalizable Model for the Galactic Center Gamma Ray Excess from Dark Matter Annihilation