Z' Mediated Dark Matter Models for the Galactic Center Gamma-Ray Excess

Abstract

With the goal of generating the Galactic Center gamma-ray excess, we revisit models in which the dark matter interacts with the Standard Model through the exchange of a new neutral gauge boson, Z'. We find several scenarios that can account for this signal, while respecting all existing constraints from colliders and direct detection experiments. In such models, the Z' either 1) couples axially to light quarks and is leptophobic, 2) couples dominantly to the third generation, or 3) is near resonance, m_Z' ~ 2 m_DM. We identify an example of an anomaly-free U(1)' that leads to an axial and leptophobic Z'. Many of the models presented here are within the reach of near future direct detection experiments, such as LUX and XENON1T.