Hidden on-shell mediators for the Galactic Centerγ-ray excess

Abstract

We present simplified models for the galactic center $\ensuremath{\gamma}$-ray excess where Dirac dark matter annihilates into pairs or triplets of on-shell bosonic mediators to the standard model. These annihilation modes allow the dark matter mass to be heavier than those of conventional effective theories for the $\ensuremath{\gamma}$-ray excess. Because the annihilation rate is set by the dark matter--mediator coupling, the standard model coupling can be made parametrically small to ``hide'' the dark sector by suppressing direct detection and collider signals. We explore the viability of these models as a thermal relic and on the role of the mediators for controlling the $\ensuremath{\gamma}$-ray spectral shape. We comment on ultraviolet completions for these simplified models and novel options for standard model final states.