Detection of Inelastic Dark Matter via Electron Recoils in SENSEI

TL;DR

This paper uses SENSEI's low-noise silicon detectors to set new constraints on inelastic light dark matter interactions with electrons, especially focusing on down-scattering processes with small mass splittings.

Contribution

It provides the first constraints on inelastic dark matter-electron scattering using SENSEI data, highlighting the stronger limits for down-scattering with negative mass splitting.

Findings

Down-scattering with negative mass splitting is more constrained.

Dark matter masses as low as 0.1 MeV are excluded for certain parameters.

SENSEI sets the most rigorous limits on inelastic DM-electron interactions to date.

Abstract

The low-threshold experiment SENSEI, which uses the ultralow-noise silicon Skipper-CCD to explore light dark matter from the halo, has achieved the most rigorous limitations on light DM-electron scattering cross section. In this work, we investigate the inelastic DM-electron scattering process with the SENSEI data and derive the constraints on the inelastic dark matter model with a $U(1)$ gauge boson as the mediator. Comparing with elastic scattering process, we find that the down-scattering process with the mass splitting $\delta \equiv m_{\chi_2}-m_{\chi_1}<0$ is more strongly constrained while the up-scattering process $\delta>0$ gets the weaker limits. For the down-scattering process with mass splitting $\delta \sim -5$ eV, the DM mass $m_{\chi}$ can be excluded down to as low as 0.1 MeV.