UC Santa Cruz

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, a right-handed neutrino model, and astroid-size primordial black holes. We showcase a new code, \mil{hazma}, developed specifically for computing constraints for each of these models. 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.