Dark Matter scattering in low threshold detectors

TL;DR

This paper investigates how sub-GeV dark matter interacts with low-threshold detectors, emphasizing collective effects and phonon interactions to accurately predict scattering rates and the Migdal effect in crystalline materials.

Contribution

It introduces a unified framework for calculating dark matter scattering rates in crystals, incorporating collective phonon effects and deriving a novel Migdal effect formula.

Findings

Derived a new formula for the Migdal effect in crystals.

Highlighted the importance of collective effects in low-energy dark matter detection.

Provided methods to calculate scattering rates for both nucleon and electron couplings.

Abstract

The scattering of sub-GeV dark matter in direct detection experiments happens at characteristic wavelengths comparable or larger than the interparticle spacing. Collective effects in the target material must therefore be accounted for when calculating the scattering rate. For dark matter-nucleon couplings, this implies matching onto the appropriate phonon effective theory and calculating single and multi-phonon scattering amplitudes. For dark matter-electron couplings, we make use of the energy loss formalism to predict the scattering rate. Combining both techniques allows us to derive a formula for the Migdal effect in crystals, which differs from prior calculations performed in atomic systems.