Solar reflection of dark matter with dark-photon mediators

TL;DR

This paper models how low-mass dark matter particles interact with the Sun via dark-photon mediators, producing a high-velocity component that enhances detection prospects in terrestrial experiments, especially for sub-MeV masses.

Contribution

It introduces a detailed Monte Carlo simulation of solar-reflected dark matter with ultralight dark-photon mediators, extending detection sensitivity to lower masses and providing new exclusion limits.

Findings

Future xenon and silicon detectors can probe dark matter as low as keV masses.

The solar-reflected dark matter flux significantly improves detection sensitivity.

Simulations and flux data are publicly available.

Abstract

We consider the scattering of low-mass halo dark-matter particles in the hot plasma of the Sun, focusing on dark matter that interact with ordinary matter through a dark-photon mediator. The resulting ``solar-reflected'' dark matter (SRDM) component contains high-velocity particles, which significantly extend the sensitivity of terrestrial direct-detection experiments to sub-MeV dark-matter masses. We use a detailed Monte-Carlo simulation to model the propagation and scattering of dark-matter particles in the Sun, including thermal effects, with special emphasis on ultralight dark-photon mediators. We study the properties of the SRDM flux, obtain exclusion limits from various direct-detection experiments, and provide projections for future experiments, focusing especially on those with silicon and xenon targets. We find that proposed future experiments with xenon and silicon targets can probe the entire ``freeze-in benchmark,'' in which dark matter is coupled to an ultralight dark photon, including dark-matter masses as low as $\mathcal{O}$(keV). Our simulations and SRDM fluxes are publicly available.