SENSEI: A Search for Diurnal Modulation in sub-GeV Dark Matter Scattering

TL;DR

This paper reports a search for daily modulation in sub-GeV dark matter signals caused by Earth's shielding effects, using SENSEI data, and sets new constraints on dark matter interactions below 1 MeV.

Contribution

It introduces a novel search for diurnal modulation in dark matter detection and improves sensitivity for MeV-scale dark matter interactions.

Findings

Order-of-magnitude better bounds on sub-MeV dark matter interactions.

Constraints on daily modulation amplitude below 6.8 electrons per gram per day.

First search for Earth's shielding effects causing diurnal modulation in this mass range.

Abstract

Dark matter particles with sufficiently large interactions with ordinary matter can scatter in the Earth's atmosphere and crust before reaching an underground detector. This Earth-shielding effect can induce a directional dependence in the dark matter flux, leading to a sidereal daily modulation in the signal rate. We perform a search for such a modulation using data from the SENSEI experiment, targeting MeV-scale dark matter. We achieve an order-of-magnitude improvement in sensitivity over previous direct-detection bounds for dark-matter masses below 1 MeV, assuming the Standard Halo Model with a Maxwell--Boltzmann velocity distribution, and constrain the amplitude of a general daily modulation signal to be below 6.8 electrons per gram per day.