Direct detection of spin-dependent sub-GeV dark matter via Migdal effect

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. (C) 2022 The Author(s). Published by Elsevier B.V.

Automated summary

Motivated by the constraints on spin-independent dark matter (DM)-nucleus scattering, this study investigates the spin-dependent interactions of light Majorana DM with nuclei mediated by an axial-vector boson. The exclusion limits on spin-dependent DM-nucleus scattering are derived using existing ionization data, with a lower limit on DM mass reaching several MeVs. The presence of a light mediator weakens the bounds on spin-dependent DM-nucleus scattering cross sections compared to a heavy mediator.