Consequences of statistical sense determination for WIMP directional detection

TL;DR

This paper analyzes how limited recoil sense determination affects the number of events needed to detect WIMP signals in directional detectors, highlighting the importance of accurate sense measurement for low-energy recoils.

Contribution

It provides a detailed study of the impact of sense determination probability on WIMP detection efficiency, including energy dependence and background effects.

Findings

Lower sense determination probability increases required events for detection.

Discarding sense information can sometimes improve detection with more events.

Correct sense measurement of low-energy recoils is crucial for minimizing event requirements.

Abstract

We study the consequences of limited recoil sense reconstruction on the number of events required to reject isotropy and detect a WIMP signal using a directional detector. For a constant probability of determining the sense correctly, 3-d read-out and zero background, we find that as the probability is decreased from 1.0 to 0.75 the number of events required to reject isotropy using the mean angle statistic is increased by a factor of a few. As the probability is decreased further the number of events required using this statistic increases sharply, and in fact isotropy can be rejected more easily by discarding the sense information and using axial statistics. This however requires an order of magnitude more events than vectorial data with perfect sense determination. We also consider energy dependent probabilities of correctly measuring the sense, 2-d read-out and non-zero background. Our main conclusion regarding the sense determination is that correctly determining the sense of the abundant, but less anisotropic, low energy recoils is most important for minimising the number of events required.