Precision Gamma-Ray Constraints for Sub-GeV Dark Matter Models

TL;DR

This paper evaluates the potential of future gamma-ray telescopes to detect sub-GeV dark matter through indirect signals, emphasizing the importance of realistic annihilation channels involving mesons and demonstrating that upcoming instruments could significantly improve current constraints.

Contribution

It introduces a method to compute dark matter annihilation into mesons using chiral perturbation theory and assesses future telescope sensitivity with the Hazma code.

Findings

Future telescopes can probe cross sections much smaller than current limits.

Realistic models involve multiple Standard Model final states, not just one.

Chiral perturbation theory enhances the accuracy of annihilation rate calculations.

Abstract

The indirect detection of dark matter particles with mass below the GeV scale has recently received significant attention. Future space-borne gamma-ray telescopes, including All-Sky-ASTROGAM, AMEGO, and GECCO, will probe the MeV gamma-ray sky with unprecedented precision, offering an exciting test of particle dark matter in the MeV-GeV mass range. While it is typically assumed that dark matter annihilates into only one Standard Model final state, this is not the case for realistic dark matter models. In this work we analyze existing indirect detection constraints and the discovery reach of future detectors for the well-motivated Higgs and vector-portal models using our publicly-available code Hazma. In particular, we show how to leverage chiral perturbation theory to compute the dark matter self-annihilation cross sections into final states containing mesons, the strongly-interacting Standard Model dynamical degrees of freedom below the GeV scale. We find that future telescopes could probe dark matter self-annihilation cross sections orders of magnitude smaller than those presently constrained by cosmic microwave background, gamma-ray and terrestrial observations.