Elastic and Inelastic Scattering of Cosmic-Rays on Sub-GeV Dark Matter

TL;DR

This paper investigates cosmic-ray interactions with sub-GeV dark matter, analyzing associated gamma-ray and neutrino signals, and derives constraints on dark matter models using multi-messenger astrophysical data.

Contribution

It introduces a comprehensive analysis of inelastic scattering signals from cosmic-ray interactions with sub-GeV dark matter, linking gamma-ray and neutrino observations to dark matter constraints.

Findings

Limits on vector portal dark matter couplings derived from gamma-ray and neutrino telescopes.

Constraints from XENON1T dominate for most dark matter masses due to low-energy scattering.

Gamma-ray and neutrino signals can serve as direct probes of dark matter interactions, complementing traditional searches.

Abstract

We revisit the signatures from collisions of cosmic-rays on sub-GeV dark matter (DM) in the Milky Way. In addition to the upscattered DM component that can be probed by existing DM and neutrino experiments widely discussed, we examine the associated signals in $\gamma$-rays and neutrinos that span a wide energy range due to the inelastic scatterings. Assuming a simple vector portal DM model for illustration, we compute both the upscattered DM flux by cosmic-ray protons, and the resulting emission of secondary $\gamma$-rays and high-energy neutrinos from proton excitation, hadronization, and the subsequent meson decay. We derive limits on coupling constants in the vector portal model using data from the $\gamma$-ray and high-energy neutrino telescopes including Fermi, H.E.S.S. and IceCube. These limits are compared to those obtained by considering the upscattered DM signals at the low-energy DM/neutrino detectors XENON1T/MiniBooNE and the IceCube. For this particular model, the limits are set predominantly by non-detection of the upscattered DM events in XENON1T, for most of the DM mass range due to the large scattering cross section at low energies. Nevertheless, our study demonstrates that the $\gamma$-ray and neutrino signals, traditionally considered as indirect probes for DM annihilation and decay, can also be directly used to constrain the DM--nucleon interaction in complementary to the direct search experiments.