Spin-dependent sub-GeV Inelastic Dark Matter-electron scattering and Migdal effect: (I). Velocity Independent Operator

TL;DR

This paper investigates sub-GeV inelastic dark matter interactions with electrons and nuclei using non-relativistic effective field theory, comparing velocity distribution models and deriving constraints from XENON1T data.

Contribution

It introduces a velocity-independent operator framework for analyzing spin-dependent inelastic dark matter scattering and compares bounds across different galactic velocity models.

Findings

Stronger exclusion limits for exothermic inelastic DM

Limits vary by up to an order of magnitude across velocity models

XENON1T data constrains spin-dependent scattering cross sections

Abstract

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.