Hidden On-Shell Mediators for the Galactic Center Gamma-Ray Excess

TL;DR

This paper introduces simplified models where on-shell mediators enable heavier dark matter particles to explain the galactic center gamma-ray excess while suppressing detection signals, offering new avenues for dark matter research.

Contribution

It proposes on-shell mediator models that allow heavier dark matter and suppress direct detection signals, expanding the theoretical framework for gamma-ray excess explanations.

Findings

Models can accommodate heavier dark matter masses.

Suppressed direct detection and collider signals.

Mediators influence gamma-ray spectral shape.

Abstract

We present simplified models for the galactic center 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 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 gamma-ray spectral shape. We comment on ultraviolet completions for these simplified models and novel options for Standard Model final states.