Spin-dependent sub-GeV inelastic dark matter-electron scattering and Migdal effect. Part I. Velocity independent operator

The ionization signal provide an important avenue of detecting light dark matter. In this work, we consider the sub-GeV inelastic dark matter and use the non-relativistic effective field theory (NR-EFT) to derive the constraints on the spin-dependent DM-electron scattering and DM-nucleus Migdal scattering. Since the recoil electron spectrum of sub-GeV DM is sensitive to tails of galactic DM velocity distributions, we also compare the bounds on corresponding scattering cross sections in Tsallis, Empirical and standard halo models. With the XENON1T data, we find that the exclusion limits of the DM-proton/neutron and DM-electron scattering cross sections for exothermic inelastic DM are much stronger that those for the endothermic inelastic DM. Each limits of the endothermic inelastic DM can differ by an order of magnitude at most in three considered DM velocity distributions.

Automated summary

In this work, ionization signals are considered as an important approach for detecting light dark matter, specifically focusing on sub-GeV inelastic dark matter. The study utilizes non-relativistic effective field theory to derive constraints on the spin-dependent DM-electron scattering and DM-nucleus Migdal scattering. The results suggest that the exclusion limits of DM-proton/neutron and DM-electron scattering cross sections are much stronger for exothermic inelastic dark matter than for endothermic inelastic dark matter.