Bracketing the impact of astrophysical uncertainties on local dark matter searches

TL;DR

This paper introduces a model-independent method to quantify how astrophysical uncertainties affect the limits on dark matter detection, showing current constraints are robust within a factor of two to ten.

Contribution

We develop a parameter to measure deviations from the standard velocity distribution, enabling bracketing of astrophysical uncertainties in dark matter searches.

Findings

Current limits are at most twice weaker than the most aggressive constraints.

Limits on dark matter mass between 10-1000 GeV are not weakened by more than a factor of 10.

Our method can be used in case of dark matter discovery to avoid bias in property reconstruction.

Abstract

The theoretical interpretation of dark matter (DM) experiments is hindered by uncertainties on the dark matter density and velocity distribution inside the Solar System. In order to quantify those uncertainties, we present a parameter that characterizes the deviation of the true velocity distribution from the standard Maxwell-Boltzmann form, and we then determine for different values of this parameter the most aggressive and most conservative limits on the dark matter scattering cross section with nuclei; uncertainties in the local dark matter density can be accounted for trivially. This allows us to bracket, in a model independent way, the impact of astrophysical uncertainties on limits from direct detection experiments and/or neutrino telescopes. We find that current limits assuming the Standard Halo Model are at most a factor of $\sim 2$ weaker than the most aggressive possible constraints. In addition, combining neutrino telescope and direct detection constraints (in a statistically meaningful way), we show that limits on DM in the mass range $\sim 10 - 1000$ GeV cannot be weakened by more than around a factor of 10, for all possible velocity distributions. We finally demonstrate that our approach can also be employed in the event of a DM discovery, allowing us to avoid bias in the reconstruction of the DM properties.