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

Understand

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.