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

6 pages, 3 figures. Version updated to match PRL version