Integrating In Dark Matter Astrophysics at Direct Detection Experiments

TL;DR

This paper explores how the MAJORANA DEMONSTRATOR can detect light WIMPs and determine their properties, emphasizing the importance of understanding the dark matter velocity distribution for accurate measurements.

Contribution

It demonstrates the potential of a neutrinoless double-beta decay experiment to also serve as a dark matter detector and analyzes the impact of velocity distribution uncertainties on WIMP property determination.

Findings

Velocity distribution uncertainties hinder WIMP mass accuracy.

Degeneracy exists between WIMP mass and velocity dispersion.

Knowledge of velocity distribution improves mass and cross section estimates.

Abstract

We study the capabilities of the MAJORANA DEMONSTRATOR, a neutrinoless double-beta decay experiment currently under construction at the Sanford Underground Laboratory, as a light WIMP detector. For a cross section near the current experimental bound, the MAJORANA DEMONSTRATOR should collect hundreds or even thousands of recoil events. This opens up the possibility of simultaneously determining the physical properties of the dark matter and its local velocity distribution, directly from the data. We analyze this possibility and find that allowing the dark matter velocity distribution to float considerably worsens the WIMP mass determination. This result is traced to a previously unexplored degeneracy between the WIMP mass and the velocity dispersion. We simulate spectra using both isothermal and Via Lactea II velocity distributions and comment on the possible impact of streams. We conclude that knowledge of the dark matter velocity distribution will greatly facilitate the mass and cross section determination for a light WIMP.