Characterization of argon recoils at the keV scale with ReD and ReD+

TL;DR

The ReD experiment measured the ionization yield of argon for low-energy nuclear recoils, providing data crucial for dark matter detection sensitivity in the 2-10 keV range.

Contribution

This work extends previous measurements of argon ionization yield below 7 keV and confirms higher yields at lower energies, aiding dark matter search experiments.

Findings

Ionization yield of argon increases at energies below 7 keV.

Results are consistent with previous data above 7 keV.

Data improves modeling of detector response for low-mass WIMP searches.

Abstract

The ReD experiment measured the ionization yield Qy of argon for nuclear recoils in the 2-10 keV range using a dual-phase Time Projection Chamber irradiated with neutrons from a Cf-252 fission source. The measurement extends coverage below 7 keV, confirms consistency with previous data above 7 keV, and indicates a higher Qy at lower energies. These results are relevant for argon-based experiments searching for dark matter in the form of low-mass Weakly Interacting Massive Particles, which are very sensitive to the modeling of the detector response in this energy range.