Azimuthal asymmetry in cosmic-ray boosted dark matter flux

Light halo dark matter (DM) particles up-scattered by high-energy cosmic rays (referred to as CRDM) can be energetic and become detectable at conventional DM and neutrino experiments. We show that the CRDM flux has a novel and detectable morphological feature. Unlike most of the recently proposed boosted DM models, which predict azimuthally symmetric DM fluxes around the Galactic Center, the CRDM flux breaks the azimuthal symmetry significantly. Using cosmic-ray electron distribution in the whole Galaxy and optimized search region in the sky according to the morphology of the CRDM flux, we derive, so far, the most stringent constraints on the DM-electron scattering cross section from the SuperKamiokande (SK) IV data, which improves the previous constraints from the SK-IV full-sky data by more than an order of magnitude. Based on the improved constraints, we predict that the azimuthal symmetrybreaking effect can be observed in the future Hyper-Kamiokande experiment at similar to 3 sigma level.

Automated summary

High-energy cosmic rays scattering with dark matter particles can be detected in conventional experiments. The flux of scattered particles shows a unique morphology, breaking the azimuthal symmetry around the Galactic Center. By using optimized search regions and cosmic-ray electron distribution data, we derived the most stringent constraints on the dark matter-electron scattering cross section, improving previous constraints significantly. These improved constraints predict the observation of azimuthal symmetry-breaking effect in future experiments at a 3 sigma level.