Revising inelastic dark matter direct detection by including the cosmic ray acceleration

TL;DR

This paper explores how cosmic-ray acceleration can enable the detection of inelastic dark matter with large mass splittings, using recent experimental data to constrain models in a new context.

Contribution

It introduces the concept of cosmic-ray accelerated inelastic dark matter detection and analyzes its potential with current experimental constraints.

Findings

Mass splitting $\, ext{<}\, ext{O}(1~{ m MeV})$ is detectable via cosmic-ray acceleration.

Detectability extends to dark matter masses between 1 MeV and 100 GeV.

Latest PandaX-4T data constrains light mediator models with cosmic-ray accelerated DM.

Abstract

The null signal from collider and dark matter (DM) direct detector experiments makes the interaction between DM and visible matter too small to reproduce the correct relic density for many thermal DM models. The remaining parameter space indicates that two almost degenerated states in the dark sector, the inelastic DM scenario, can co-annihilate in the early universe to produce the correct relic density. Regarding the direct detection of the inelastic DM scenario, the virialized DM component from the nearby halo is nonrelativistic and not able to excite the DM ground state, even if the relevant couplings can be considerable. Thus, a DM with a large mass splitting can evade traditional virialized DM direct detection. In this study, we connect the concept of cosmic-ray accelerated DM in our Milky Way and the direct detection of inelastic scattering in underground detectors to explore spectra that result from several interaction types of the inelastic DM. We find that the mass splitting $\delta<\mathcal{O}(1~{\rm MeV})$ can still be reachable for cosmic ray accelerated DM with mass range $1~{\rm MeV}<m_{\chi_1}<100~{\rm GeV}$ and sub-GeV light mediator using the latest PandaX-4T data, even though we conservatively use the astrophysical parameter (effective length) $D_{\rm eff}=1$ kpc.