Dark magnetic dipole property in fermionic absorption by nucleus and electrons

TL;DR

This paper investigates how fermionic dark matter with magnetic dipole moments can be detected through absorption by nuclei and electrons, producing distinctive signals that can be observed in current and future experiments.

Contribution

It introduces a model of fermionic dark matter with magnetic dipole interactions and analyzes its detection prospects via nuclear recoil and electron ionization signals.

Findings

XENON1T can probe DM masses above 27 MeV.

Projected constraints on inelastic DM-nucleon cross section are around 10^{-49} cm^2.

Future experiments like CRESSTIII can detect DM above 2 MeV.

Abstract

The fermionic dark matter (DM) absorption by nucleus or electron targets provides a distinctive signal to search for sub-GeV DM. We consider a Dirac fermion DM charged under a dark gauge group and with the dark magnetic dipole operator. The DM field mixes with right-handed neutrino and interacts with the ordinary electromagnetic charge current via the kinetic mixing term of gauge fields. As a result, the incoming DM is absorbed and converted into neutrino in final state through the dipole-charge interaction. For the DM absorption by nucleus, the recoil energy spectrum exhibit a peak at $m_\chi^2/2m_N$ for each isotope in the target. XENON1T can probe the DM mass above 27 MeV and the projected constraint on the inelastic DM-nucleon cross section becomes $10^{-49}$ cm$^2$. CRESSTIII with lower energy threshold would be sensitive to the DM mass above 2 MeV. We also check that the contribution from the nuclear magnetic dipole is negligible for $^{131}{\rm Xe}$ target. The absorption of DM by bound electron target induces ionization signal and is sensitive to sub-MeV DM mass. The involvement of the ionization form factor spreads out the localized recoil energy. We show the future prospect for the constraint on the magnetic dipole coupling from the electron ionization of $^{131}{\rm Xe}$.