Effect of inelastic scattering on cosmic-ray-boosted dark matter

Abstract: Sub-GeV dark matter particles evade standard direct detection studies since their typical energies in the galactic halo do not allow for detectable recoil of the heavy nuclei in the detectors. However, it was noted that if the dark matter particles have sizable couplings to nucleons, they can be boosted by interactions with galactic cosmic rays and probed by experiments like Xenon-1T. We revisit the resulting bounds on DM-nucleon interaction and improve on previous works by considering the DM-nucleus inelastic cross sections provided by the GENIE interaction event generator. Including inelastic scattering in the process of dark matter boosting increases the flux of high-energy dark matter coming to Earth. Additionally, allowing for inelastic scattering with nuclei is important for a realistic description of the dark matter interacting in the Earth's crust. We demonstrate these effects on a benchmark model where dark matter interactions are mediated by a dark U(1) vector boson.