Dark matter substructures affect dark matter-electron scattering in xenon-based direct detection experiments

TL;DR

This paper investigates how dark matter substructures influence electron recoil detection rates in xenon-based experiments, highlighting the potential to detect and resolve substructure fractions, especially for low-mass dark matter around 10 MeV.

Contribution

It introduces the impact of dark matter substructures on direct detection signals and assesses the experiments' ability to identify and quantify these substructures.

Findings

Dark matter substructures can significantly affect electron recoil detection rates.

Experiments can resolve substructure fractions with good accuracy for ~10 MeV dark matter.

Detection sensitivity improves with lower electron thresholds and exposure.

Abstract

Recent sky surveys have discovered a large number of stellar substructures. It is highly likely that there are dark matter (DM) counterparts to these stellar substructures. We examine the implications of DM substructures for electron recoil (ER) direct detection (DD) rates in dual phase xenon experiments. We have utilized the results of the LAMOST survey and considered a few benchmark substructures in our analysis. Assuming that these substructures constitute $\sim 10\%$ of the local DM density, we study the discovery limits of DM-electron scattering cross sections considering one kg-year exposure and 1, 2, and 3 electron thresholds. With this exposure and threshold, it is possible to observe the effect of the considered DM substructure for the currently allowed parameter space. We also explore the sensitivity of these experiments in resolving the DM substructure fraction. For all the considered cases, we observe that DM having mass $\mathcal{O}(10)\,$MeV has a better prospect in resolving substructure fraction as compared to $\mathcal{O}(100)\,$MeV scale DM. We also find that within the currently allowed DM-electron scattering cross-section; these experiments can resolve the substructure fraction (provided it has a non-negligible contribution to the local DM density) with good accuracy for $\mathcal{O}(10)\,$MeV DM mass with one electron threshold.