Direct Detection of Spin-Dependent Sub-GeV Dark Matter via Migdal Effect

TL;DR

This paper explores the detection of light spin-dependent dark matter particles using the Migdal effect, deriving new exclusion limits in the MeV-GeV mass range with existing ionization data.

Contribution

It introduces a novel approach to constrain light spin-dependent dark matter via the Migdal effect, considering light mediators and existing ionization data.

Findings

Exclusion limits on SD DM-nucleus scattering derived for MeV-GeV DM mass range.

Lower DM mass limit can reach about several MeVs.

Bounds are weaker with light mediators compared to heavy mediators.

Abstract

Motivated by the current strong constraints on the spin-independent dark matter (DM)-nucleus scattering, we investigate the spin-dependent (SD) interactions of the light Majorana DM with the nucleus mediated by an axial-vector boson. Due to the small nucleus recoil energy, the ionization signals have now been used to probe the light dark matter particles in direct detection experiments. With the existing ionization data, we derive the exclusion limits on the SD DM-nucleus scattering through Migdal effect in the MeV-GeV DM mass range. It is found that the lower limit of the DM mass can reach about several MeVs. Due to the momentum transfer correction induced by the light mediator, the bounds on the SD DM-nucleus scattering cross sections can be weakened in comparison with the heavy mediator.