First Observation of Single Photons in a CRESST Detector and New Dark Matter Exclusion Limits

The main goal of the CRESST-III experiment is the direct detection of darkmatter particles via their scattering off target nuclei in cryogenic detectors.In this work we present the results of a Silicon-On-Sapphire (SOS) detectorwith a mass of 0.6g and an energy threshold of (6.7±0.2)eVwith a baseline energy resolution of (1.0±0.2)eV. This allowedfor a calibration via the detection of single luminescence photons in theeV-range, which could be observed in CRESST for the first time. We present newexclusion limits on the spin-independent and spin-dependent dark matter-nucleoncross section that extend to dark matter particle masses of less than100MeV/c^2.