Constraints on Sub-GeV Dark Matter–Electron Scattering from the CDEX-10 Experiment

Abstract

We present improved germanium-based constraints on sub-GeV dark matter via dark matter--electron ($\ensuremath{\chi}\text{\ensuremath{-}}e$) scattering using the $205.4\text{ }\text{ }\mathrm{kg}\ifmmode\cdot\else\textperiodcentered\fi{}\mathrm{day}$ dataset from the CDEX-10 experiment. Using a novel calculation technique, we attain predicted $\ensuremath{\chi}\text{\ensuremath{-}}e$ scattering spectra observable in high-purity germanium detectors. In the heavy mediator scenario, our results achieve 3 orders of magnitude of improvement for ${m}_{\ensuremath{\chi}}$ larger than $80\text{ }\text{ }\mathrm{MeV}/{\mathrm{c}}^{2}$ compared to previous germanium-based $\ensuremath{\chi}\text{\ensuremath{-}}e$ results. We also present the most stringent $\ensuremath{\chi}\text{\ensuremath{-}}e$ cross-section limit to date among experiments using solid-state detectors for ${m}_{\ensuremath{\chi}}$ larger than $90\text{ }\text{ }\mathrm{MeV}/{\mathrm{c}}^{2}$ with heavy mediators and ${m}_{\ensuremath{\chi}}$ larger than $100\text{ }\text{ }\mathrm{MeV}/{\mathrm{c}}^{2}$ with electric dipole coupling. The result proves the feasibility and demonstrates the vast potential of a new $\ensuremath{\chi}\text{\ensuremath{-}}e$ detection method with high-purity germanium detectors in ultralow radioactive background.