A NaI-Based Cryogenic Scintillating Calorimeter: Results from a COSINUS Prototype Detector

The Cryogenic Observatory for SIgnals seen in Next-generation Underground Searches (COSINUS) project aims to provide a model-independent cross-check of the long-standing DAMA/LIBRA claim on the observation of dark matter by using the same target material, but in a different experimental approach. Operating sodium iodide (NaI) scintillating crystals as low-temperature scintillating calorimeters has the distinct advantage of providing a lower energy threshold for nuclear recoil events as expected from dark matter particle interactions combined with particle discrimination. The dual readout of phonon and light allows us to provide background rejection on an event-by-event basis, a unique feature in comparison with other NaI-based dark matter searches. The manuscript discusses in detail the COSINUS detector concept and presents the results and performance parameters from our second prototype detector.