Search for sub-GeV dark matter by annual modulation using XMASS-I detector
M. Kobayashi (Kamioka Observatory, Institute for Cosmic Ray Research, the University of Tokyo, Hida, Japan); K. Abe (Kamioka Observatory, Institute for Cosmic Ray Research, the University of Tokyo, Hida, Japan, Kavli Institute for the Physics and Mathematics of the Universe (WPI), the University of Tokyo, Kashiwa, Japan); K. Hiraide (Kamioka Observatory, Institute for Cosmic Ray Research, the University of Tokyo, Hida, Japan, Kavli Institute for the Physics and Mathematics of the Universe (WPI), the University of Tokyo, Kashiwa, Japan); K. Ichimura (Kamioka Observatory, Institute for Cosmic Ray Research, the University of Tokyo, Hida, Japan, Kavli Institute for the Physics and Mathematics of the Universe (WPI), the University of Tokyo, Kashiwa, Japan); Y. Kishimoto (Kamioka Observatory, Institute for Cosmic Ray Research, the University of Tokyo, Hida, Japan, Kavli Institute for the Physics and Mathematics of the Universe (WPI), the University of Tokyo, Kashiwa, Japan); et al - Show all 36 authors
A search for dark matter (DM) with mass in the sub-GeV region (0.32–1 GeV) was conducted by looking for an annual modulation signal in XMASS, a single-phase liquid xenon detector. Inelastic nuclear scattering accompanied by bremsstrahlung emission was used to search down to an electron equivalent energy of 1 keV. The data used had a live time of 2.8 years (3.5 years in calendar time), resulting in a total exposure of 2.38 ton-years. No significant modulation signal was observed and 90% confidence level upper limits of cm$^{2}$ at 0.5 GeV was set for the DM-nucleon cross section. This is the first experimental result of a search for DM mediated by the bremsstrahlung effect. In addition, a search for DM with mass in the multi-GeV region (4–20 GeV) was conducted with a lower energy threshold than previous analysis of XMASS. Elastic nuclear scattering was used to search down to a nuclear recoil equivalent energy of 2.3 keV, and upper limits of 2.9 × cm$^{2}$ at 8 GeV was obtained.