An Attractive Scenario for Light Dark Matter Direct Detection

TL;DR

This paper proposes a scenario where an attractive long-range force sourced by ordinary matter accelerates light dark matter towards Earth, boosting detection prospects and potentially explaining recent experimental excesses.

Contribution

It introduces a novel attractive force mechanism that increases dark matter velocities and densities near Earth, enhancing direct detection sensitivity for light dark matter.

Findings

Dark matter can reach velocities ~0.1 near Earth's surface due to the attractive force.

Enhanced dark matter density at Earth improves detection prospects.

Parameters consistent with stellar cooling bounds could explain XENON1T excess.

Abstract

Direct detection of light dark matter (DM), below the GeV scale, through electron recoil can be efficient if DM has a velocity well above the virial value of $v\sim 10^{-3}$. We point out that if there is a long range attractive force sourced by bulk ordinary matter, i.e. baryons or electrons, DM can be accelerated towards the Earth and reach velocities $v\sim 0.1$ near the Earth's surface. In this "attractive scenario," all DM will be boosted to high velocities by the time it reaches direct detection apparatuses in laboratories. Furthermore, the attractive force leads to an enhanced DM number density at the Earth facilitating DM detection even more. We elucidate the implications of this scenario for electron recoil direct detection experiments and find parameters that could lead to potential signals, while being consistent with stellar cooling and other bounds. Our scenario can potentially explain the recent excess in electron recoil signals reported by the XENON1T experiment in the $\sim$ keV energy regime as well as the hint for non-standard stellar cooling.