Dark matter direct detection from the single phonon to the nuclear recoil regime

TL;DR

This paper develops a comprehensive model for dark matter detection in crystal detectors, covering from single phonon to nuclear recoil regimes, and introduces a public tool for the community.

Contribution

It provides the first calculation of multiphonon production rates across the full keV-GeV dark matter mass range, unifying different detection regimes.

Findings

Calculated multiphonon scattering rates for the entire mass range.

Connected single phonon, multiphonon, and nuclear recoil regimes analytically.

Implemented results in the public package DarkELF.

Abstract

In most direct detection experiments, the free nuclear recoil description of dark matter scattering breaks down for masses $\lesssim$ 100 MeV, or when the recoil energy is comparable to a few times the typical phonon energy. For dark matter lighter than 1 MeV, scattering via excitation of a single phonon dominates and has been computed previously, but for the intermediate mass range or higher detector thresholds, multiphonon processes dominate. We perform the first calculation of the scattering rate via multiphonon production for the entire keV-GeV dark matter mass range, assuming a harmonic crystal target. We provide an analytic description that connects the single phonon, multiphonon, and the nuclear recoil regimes. Our results are implemented in the public package $\texttt{DarkELF}$.