Constraints on cosmic-ray boosted dark matter in CDEX-10 * *Supported in part by Guangdong Basic and Applied Basic Research Foundation (2019A1515012216), National Undergraduate Innovation and Entrepreneurship Training Program (20201023) and the CAS Center for Excellence in Particle Physics (CCEPP)

Abstract

Dark matter (DM) direct detection experiments have been setting strong limits on the DM–nucleon scattering cross section at the DM mass above a few GeV, but leave large parameter spaces unexplored in the low mass region. DM is likely to be scattered and boosted by relativistic cosmic rays in the expanding universe if it can generate nuclear recoils in direct detection experiments to offer observable signals. Since low energy threshold detectors using Germanium have provided good constraints on ordinary halo GeV-scale DM, it is necessary to re-analyze 102.8 kg day data in the CDEX-10 experiment assuming that DM is boosted by cosmic rays. For the DM mass range 1 keV 1 MeV and the effective distance within 1 kpc, we reach an almost flat floor limit at cm2 for the spin-independent DM–nucleon scattering cross section, at a 90% confidence level. The CDEX-10 result is able to close the gap unambiguously in the parameter space between the MiniBooNE and XENON1T constraints, which were partially hindered by the Earth attenuation effect. We also quantitatively calculate the expected neutrino floor on searching for CRBDM in future direct detection experiments using Germanium.