Dark matter astrometry at underground detectors with multiscatter events

TL;DR

This paper demonstrates that underground detectors can perform precise dark matter astrometry by reconstructing dark matter trajectories from multiscatter events, enabling detailed analysis of dark matter velocity distributions with minimal events.

Contribution

It introduces a method to reconstruct dark matter velocity vectors event-by-event using multiscatter tracks, advancing dark matter detection and characterization capabilities.

Findings

Dark matter velocity can be reconstructed with small uncertainty.

As few as 10 events can distinguish dark matter signals from backgrounds.

Dark matter halo properties can be inferred from reconstructed velocities.

Abstract

We show that current and imminent underground detectors are capable of precision astrometry of dark matter. First we show that galactic dark matter velocity distributions can be obtained from reconstructed tracks of dark matter scattering on multiple nuclei during transit; using the liquid scintillator neutrino detector SNO+ as an example, we find that the dark matter velocity vector can be reconstructed event-by-event with such a small uncertainty, that the precision of dark matter astrometry will be limited mainly by statistics. We then determine the number of dark matter events required to determine the dispersion speed, escape speed, and velocity anisotropies of the local dark matter halo, and also find that with as few as $\mathcal{O}(10)$ events, dark matter signals may be discriminated from potential backgrounds arising as power-law distributions. Finally, we discuss the prospects of dark matter astrometry at other liquid scintillator detectors, dark matter experiments, and the recently proposed MATHUSLA detector.