Directional detection of dark matter streams

TL;DR

Future directional dark matter detectors could effectively identify and characterize dark matter streams, such as Sagittarius-like streams, by measuring nuclear recoil energies and directions, even with modest exposure times.

Contribution

This study demonstrates the potential of upcoming directional detectors to detect and analyze dark matter streams across various parameters, expanding the scope of dark matter substructure detection.

Findings

Detectors can probe a wide range of stream velocities and densities.

Sensitivity achievable with around 10 kg-year exposure for near-current cross section limits.

Energy window of the detector significantly impacts detection capabilities.

Abstract

Directional detection of WIMPs, in which the energies and directions of the recoiling nuclei are measured, currently presents the only prospect for probing the local velocity distribution of Galactic dark matter. We investigate the extent to which future directional detectors would be capable of probing dark matter substructure in the form of streams. We analyse the signal expected from a Sagittarius-like stream and also explore the full parameter space of stream speed, direction, dispersion and density. Using a combination of non-parametric directional statistics, a profile likelihood ratio test and Bayesian parameter inference we find that within acceptable exposure times (O(10) kg yr for cross sections just below the current exclusion limits) future directional detectors will be sensitive to a wide range of stream velocities and densities. We also examine and discuss the importance of the energy window of the detector.