Producing the GeV Galactic Center Excess via Cosmic Ray-Dark Matter Scattering

TL;DR

This paper introduces a new mechanism where cosmic-ray protons scatter off dark matter in the Milky Way halo, producing gamma rays that could explain the Galactic Center excess, offering an alternative to dark matter annihilation models.

Contribution

It proposes a novel cosmic-ray scattering framework for gamma-ray production, with specific models that fit the observed excess spectrum.

Findings

The framework can produce gamma-ray signals matching the Galactic Center excess.

Both inelastic and elastic dark matter models are viable within this framework.

The models provide fits comparable to traditional dark matter annihilation explanations.

Abstract

In this work, we propose a novel mechanism for generating gamma rays from the Galactic Center via scattering of cosmic-ray protons off dark matter in the Milky Way halo, in contrast to conventional explanations based on dark matter annihilation. We present two examples of this framework that produce an observable photon signal. In the inelastic dark matter model, cosmic rays up-scatter a lighter dark matter particle, with the subsequent decay of the heavier particle yielding two photons. In the elastic dark matter model, an energetic photon is directly produced in the final state of a 2-to-3 scattering process. We show that, for a range of viable model parameters, this framework provides a fit to the observed Galactic Center gamma-ray excess spectrum comparable to those obtained from dark matter annihilation and millisecond pulsar models. Our results open a new avenue for interpreting gamma-ray observations of the Galactic Center.