  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.
