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.
@article{arxiv.2510.20889,
title = {SENSEI: A Search for Diurnal Modulation in sub-GeV Dark Matter Scattering},
author = {Itay M. Bloch and Ana M. Botti and Mariano Cababie and Gustavo Cancelo and Brenda A. Cervantes-Vergara and Miguel Daal and Ansh Desai and Alex Drlica-Wagner and Rouven Essig and Juan Estrada and Erez Etzion and Guillermo Fernandez Moroni and Stephen E. Holland and Jonathan Kehat and Ian Lawson and Steffon Luoma and Aviv Orly and Santiago E. Perez and Dario Rodrigues and Nathan A. Saffold and Silvia Scorza and Miguel Sofo-Haro and Kelly Stifter and Javier Tiffenberg and Sho Uemura and Edgar Marrufo Villalpando and Tomer Volansky and Federico Winkel and Yikai Wu and Tien-Tien Yu and Xavier Bertou},
journal= {arXiv preprint arXiv:2510.20889},
year = {2025}
}