Spin-Dependent Scattering of Sub-GeV Dark Matter: Models and Constraints

TL;DR

This paper analyzes the scattering mechanisms of sub-GeV spin-dependent dark matter in solid-state detectors, deriving constraints from various experiments and exploring detection prospects for different mass ranges.

Contribution

It introduces a comprehensive calculation of spin-dependent dark matter scattering in solid targets, connecting phonon and nuclear recoil regimes, and derives new bounds considering multiple mediators and experimental data.

Findings

Incoherent phonon production dominates for dark matter below 100 MeV.

Existing experimental bounds are very stringent for most parameter space.

Potential for direct detection of dark matter above 100 MeV depending on experimental exposure.

Abstract

We calculate the scattering rate of sub-GeV dark matter in solid-state targets for spin-dependent dark matter -- nucleon interactions. For dark matter particles with mass below 100 MeV, the scattering occurs predominantly through incoherent phonon production. For dark matter heavier than 100 MeV, we match onto the nuclear recoil calculation. To compare the sensitivity of future direct detection experiments with existing constraints, we consider three models with interactions which are mediated by spin-0 or spin-1 particles. This allows us to derive bounds on the cross section from searches for the mediating particle, including bounds from stellar cooling, beam dump experiments, meson factories and dark matter self-interactions. The existing bounds are very stringent, though for $m_\chi\gtrsim 100$ MeV there is parameter space which may be accessible with direct detection, depending on the exposure and background rates.