Plasma dark matter direct detection

TL;DR

This paper models dark plasma as a magnetohydrodynamic fluid to explore its interactions with Earth and implications for direct detection experiments, including potential explanations for DAMA signals.

Contribution

It introduces a fluid model of dark plasma using magnetohydrodynamics to analyze its effects on direct detection signals and explores new detection signatures.

Findings

Dark plasma can produce keV electron recoils in detectors.

Magnetohydrodynamic modeling reveals complex plasma interactions with Earth.

Possible explanation for DAMA's annual modulation signal.

Abstract

Dark matter in spiral galaxies like the Milky Way may take the form of a dark plasma. Hidden sector dark matter charged under an unbroken $U(1)'$ gauge interaction provides a simple and well defined particle physics model realising this possibility. The assumed $U(1)'$ neutrality of the Universe then implies (at least) two oppositely charged dark matter components with self-interactions mediated via a massless "dark photon" (the $U(1)'$ gauge boson). In addition to nuclear recoils such dark matter can give rise to keV electron recoils in direct detection experiments. In this context, the detailed physical properties of the dark matter plasma interacting with the Earth is required. This is a complex system, which is here modelled as a fluid governed by the magnetohydrodynamic equations. These equations are numerically solved for some illustrative examples, and implications for direct detection experiments discussed. In particular, the analysis presented here leaves open the intriguing possibility that the DAMA annual modulation signal is due primarily to electron recoils (or even a combination of electron recoils and nuclear recoils). The importance of diurnal modulation (in addition to annual modulation) as a means of probing this kind of dark matter is also emphasised.