Boosting Asymmetric Charged DM via Thermalization

TL;DR

This paper introduces a new mechanism where a large mass hierarchy in a dark sector with opposite charges leads to thermalization and boosting of lighter dark matter particles, enhancing their detectability in experiments.

Contribution

The paper proposes a novel boosting mechanism for dark matter particles based on thermalization in a charged dark sector with a significant mass hierarchy.

Findings

Boosted dark matter particles can reach velocities above galactic escape speeds.

Current and future experiments can detect boosted dark matter down to 100 keV.

The scenario is viable for dark sector making up 5% of total dark matter with mass ratios of 10^3-10^4.

Abstract

We consider a dark sector scenario with two dark matter species with opposite dark $U(1)$ charges and an asymmetric population comprising some fraction of the dark matter abundance. A new mechanism for boosting dark matter is introduced, arising from the large mass hierarchy between the two particles. In the galaxy, the two species thermalize efficiently through dark Rutherford scattering greatly boosting the lighter dark matter particle, far above the virial and escape velocities in the galaxy, while the dark charge prevents it from escaping. We study the consequences of this scenario for direct-detection experiments, assuming a kinetic mixing between the dark photon and the photon. If the charged dark sector makes up 5% of the total DM mass in our galaxy and the mass ratio is between $10^3-10^4$, we find that current and future experiments may probe the boosted light dark matter for masses down to 100 keV, in a hitherto unexplored parameter range.