Dependence of Dark Matter - Electron Scattering on the Galactic Dark Matter Velocity Distribution

TL;DR

This paper examines how different dark matter halo models and their parameters influence the predicted dark matter-electron scattering rates, emphasizing the importance of the high-velocity tail in these models.

Contribution

It provides a comprehensive analysis of various halo models, updates parameter values, and quantifies how model choices affect scattering rate predictions and cross-section limits.

Findings

Scattering rate predictions vary significantly with halo model parameters.

High-velocity tail sensitivity impacts detection rate estimates.

Changes in circular velocity v0 cause rate variations from 0.01% to 100%.

Abstract

The rate of dark matter-electron scattering depends on the underlying velocity distribution of the dark matter halo. Importantly, dark matter-electron scattering is particularly sensitive to the high-velocity tail, which differs significantly amongst the various dark matter halo models. In this work, we summarize the leading halo models and discuss the various parameters which enter them. We recommend updated values for these parameters based on recent studies and measurements. Furthermore, we quantify the dependence of the dark matter-electron scattering rate on the choice of halo model and parameters, and demonstrate how these choices propagate to the predicted cross-section limits. The rate is most sensitive to changes in the circular velocity v0; in silicon targets, we find that the changes in the rate predictions can range from O(0.01%) to O(100%) for contact interactions and O(10%) to O(100%) for long-range interactions.