Constraining light dark matter upscattered by ultrahigh-energy cosmic rays

Light halo dark matter (DM) particles upscattered by high-energy cosmic rays (CRs) can be energetic, and become detectable by conventional direct detection experiments. The current constraints derived from space-based direct CR measurements can reach O(10(-31)) cm(2) for a constant DM-nucleon scattering cross section. We show that if the CR energy spectrum follows a power law of type similar to E-3, the derived constraints on the scattering cross section will be highly insensitive to DM particle mass. This suggests that ultrahigh-energy CRs (UHECRs) indirectly measured by ground-based detectors can be used to place constraints on ultralight DM particles, as E-3 is a very good approximation of the UHECR energy spectrum up to energy similar to 10(20) eV. Using the recent UHECR flux data, we show that the current constraints derived from space-based CR measurements can in principle be extended to ultralight DM particles far below eV scale. (C) 2021 The Author(s). Published by Elsevier B.V.

Automated summary

The study shows that constraints on dark matter particle scattering cross section are not highly sensitive to the mass of the dark matter particle when the cosmic ray energy spectrum follows a power law of type similar to E-3. Additionally, ultrahigh-energy cosmic rays indirectly measured by ground-based detectors can be used to place constraints on ultralight dark matter particles.