Limits on Low-Mass WIMP Dark Matter with an Ultra-Low-Energy Germanium Detector at 220 eV Threshold

The theme of the TEXONO research program is on the studies of low energy neutrino and dark matter physics. The current goals of the TEXONO research program are on the development of germanium detectors with sub-keV sensitivities to realize experiments on neutrino magnetic moments, neutrino-nucleus coherent scattering, as well as WIMP dark matter searches. An energy threshold of 220 eV was achieved with a four-channel ultra-low-energy germanium prototype detector each with an active mass of 5 g at the Kuo-Sheng Neutrino Laboratory. New limits were placed for the couplings of low-mass WIMPs with matter. Data are being taken with a 500 g Point Contact Germanium detector, where a threshold of ∼350 eV was demonstrated. The dark matter program will evolve into a dedicated experiment at an underground laboratory under construction in Sichuan, China.