First measurement of the Head-Tail directional nuclear recoil signature at energies relevant to WIMP dark matter searches

TL;DR

This paper reports the first detection of the Head-Tail asymmetry in nuclear recoil tracks at energies relevant for WIMP dark matter searches, using a specialized detector to identify potential dark matter signals.

Contribution

It provides the first evidence of the Head-Tail asymmetry signature at low energies, demonstrating its potential for WIMP detection in dark matter experiments.

Findings

Detected Head-Tail asymmetry down to 1.5 keV/amu

Recoil distributions match WIMP expectations

Open new avenues for galactic WIMP signature searches

Abstract

We present first evidence for the so-called Head-Tail asymmetry signature of neutron-induced nuclear recoil tracks at energies down to 1.5 keV/amu using the 1m^3 DRIFT-IIc dark matter detector. This regime is appropriate for recoils induced by Weakly Interacting Massive Particle (WIMPs) but one where the differential ionization is poorly understood. We show that the distribution of recoil energies and directions induced here by Cf-252 neutrons matches well that expected from massive WIMPs. The results open a powerful new means of searching for a galactic signature from WIMPs.