Present and future status of light dark matter models from cosmic-ray electron upscattering

Nonrelativistic dark matter (DM) can be accelerated by scattering on high-energy cosmic-ray (CR) electrons. This process leads to a subpopulation of relativistic or semirelativistic DM which extends the experimental reach for direct detection in the sub-GeV mass regime. In this paper we examine the current and future potential of this mechanism for constraining models of light dark matter. In particular, we find that Super-Kamiokande and XENON1T data can already provide leading constraints on the flux of dark matter that has been accelerated to high energies from cosmic ray electrons. We also examine future projected sensitivities for DUNE and Hyper-K, and contrary to previous findings, conclude that DUNE will be able supersede Super-K bounds on cosmic-ray upscattered DM for a variety of DM models.