Production and attenuation of cosmic-ray boosted dark matter

TL;DR

This paper refines bounds on cosmic-ray boosted dark matter detection by incorporating spatial-dependent cosmic-ray fluxes and nuclear form factors, revealing that Earth attenuation effects are less restrictive than previously thought, thus expanding the detectable parameter space.

Contribution

It provides a more accurate analysis of the exclusion bounds on dark matter-nucleon cross sections by including detailed cosmic-ray flux modeling and nuclear form factors, improving the understanding of detection limits.

Findings

Effective distance for CRDM production is about 9 kpc.

Exclusion lower bounds on cross section reach ~4×10⁻³² cm² for MeV-scale DM.

Nuclear form factors significantly reduce Earth attenuation effects.

Abstract

Light sub-GeV halo dark matter (DM) particles up-scattered by high-energy cosmic-rays (CRs) (referred to as CRDM) can be energetic and become detectable by conventional DM direct detection experiments. We perform a refined analysis on the exclusion bounds of the spin-independent DM-nucleon scattering cross section $\sigma_{\chi p}$ in this approach. For the exclusion lower bounds, we determine the parameter of the effective distance $D_\text{eff}$ for CRDM production using spatial-dependent CR fluxes and including the contributions from the major heavy CR nuclear species. We obtain $D_\text{eff}\simeq 9$ kpc for CRDM particles with kinetic energy above $\sim 1~\text{GeV}$, which pushes the corresponding exclusion lower bounds down to $\sigma_{\chi p} \sim 4\times 10^{-32}~\text{cm}^2$ for DM particle mass at MeV scale and below. For the exclusion upper bounds from Earth attenuation, previous estimations neglecting the nuclear form factor leaded to typical exclusion upper bounds of $\sigma_{\chi p}\sim\mathcal{O}(10^{-28})~\text{cm}^2$ from the XENON1T data. Using both the analytic and numerical approaches, we show that for CRDM particles, the presence of the nuclear form factor strongly suppresses the effect of Earth attenuation. Consequently, the cross section that can be excluded by the XENON1T data can be a few orders of magnitude higher, which closes the gap in the cross sections excluded by the XENON1T experiment and that by the astrophysical measurements such that for the cosmic microwave background (CMB), galactic gas cloud cooling, and structure formation, etc..