The impact of going beyond the Maxwell distribution in direct dark matter detection rates

TL;DR

This paper compares standard Maxwell-Boltzmann velocity distributions with more realistic distributions from simulations to assess their impact on dark matter detection rates and annual modulation signals.

Contribution

It introduces the use of simulation-based velocity distributions in dark matter detection models, highlighting significant differences from traditional assumptions.

Findings

Light targets see ~25% reduction in rate and modulation

Heavy targets have unchanged total rate but up to 50% modulation change

Velocity anisotropy can reduce annual modulation, especially for light targets

Abstract

We consider direct dark matter detection rates and investigate the difference between a standard Maxwell-Boltzmann velocity distribution and a "realistic" distribution like the ones extracted from numerical N-body simulations. Sizable differences are observed when such results are compared to the standard Maxwell-Boltzmann distribution. For a light target both the total rate and the annual modulation are reduced by ~25%. For a heavy target the total rate is virtually unchanged, whereas the annual modulation is modified by up to 50%, depending on the WIMP mass and detector energy threshold. We also consider the effect of a possible velocity anisotropy, and the effect is found to be largest for a light target For the realistic velocity distribution the anisotropy may reduce the annual modulation, in contrast to the Maxwell-Boltzmann case.