Earth-Scattering Induced Modulation in Low-Threshold Dark Matter Experiments

TL;DR

This paper studies how Earth-induced scattering modulates signals in low-threshold dark matter detectors, offering a new way to detect sub-GeV dark matter particles by analyzing sidereal day variations.

Contribution

It provides detailed calculations of Earth-scattering effects on dark matter signals and explores the potential of modulation searches to probe new parameter space.

Findings

Modulation signals can be detected near current experiment thresholds.

Earth scattering significantly affects dark matter detection signals.

Future experiments can improve sensitivity using modulation analysis.

Abstract

Dark matter particles with sufficiently large interactions with ordinary matter can scatter in the Earth before reaching and scattering in a detector. This induces a modulation in the signal rate with a period of one sidereal day. We calculate this modulation for sub-GeV dark matter particles that interact either with a heavy or an ultralight dark-photon mediator and investigate the resulting signal in low-threshold detectors consisting of silicon, xenon, or argon targets. The scattering in the Earth is dominated by dark matter scatters off nuclei, while the signal in the detector is easiest to observe from dark matter scattering off electrons. We investigate the properties of the modulation signal and provide projections of the sensitivity of future experiments. We find that a search for a modulation signal can probe new regions of parameter space near the energy thresholds of current experiments, where the data are typically dominated by backgrounds.