Low Threshold Results and Limits from the DRIFT Directional Dark Matter Detector

TL;DR

This paper reports on the latest results from the DRIFT-IId detector, achieving lower detection thresholds and improved gamma rejection, setting new limits on dark matter interactions, and analyzing neutron backgrounds in underground conditions.

Contribution

It introduces a lower threshold detection method and improved analysis for the DRIFT-IId detector, enhancing sensitivity to dark matter signals.

Findings

No events in the fiducial region lead to new exclusion limits on WIMP-proton interactions.

Achieved a fourfold improvement in exclusion limits compared to previous work.

Observed nuclear recoil rate consistent with ambient neutron background.

Abstract

We present results from a 54.7 live-day shielded run of the DRIFT-IId detector, the world's most sensitive, directional, dark matter detector. Several improvements were made relative to our previous work including a lower threshold for detection, a more robust analysis and a tenfold improvement in our gamma rejection factor. After analysis, no events remain in our fiducial region leading to an exclusion curve for spin-dependent WIMP-proton interactions which reaches 0.28 pb at 100 GeV/c^2 a fourfold improvement on our previous work. We also present results from a 45.4 live-day unshielded run of the DRIFT-IId detector during which 14 nuclear recoil-like events were observed. We demonstrate that the observed nuclear recoil rate of 0.31+/-0.08 events per day is consistent with detection of ambient, fast neutrons emanating from the walls of the Boulby Underground Science Facility.