COSINUS Conceptual Design Report

Today astronomical observations on all length scales provide overwhelming evidence for the existence of non-baryonic dark matter in the universe. The microscopic nature of dark matter, however, still remains unclear. Numerous direct dark matter searches aim to detect nuclear recoils induced by dark matter particles in earth-bound detectors. While most experiments report no potential dark matter signal, the DAMA/LIBRA collaboration claims evidence for a dark matter signal identified via an annual modulation of the event rate in their NaI target crystals. This puzzling situation can only be resolved with model-independent cross-checks which may solely be provided by experiments also using NaI as a target material. All NaI-based experimental efforts use NaI as room-temperature scintillation detectors. Only COSINUS goes a step further by operating NaI as a cryogenic detector. This operating mode yields a lower threshold for nuclear recoils, a more precise reconstruction of the deposited energy and particle discrimination between electron and nuclear recoils on an event-by-event basis. These unique features will allow COSINUS not only to confirm or reject the DAMA/LIBRA claim, but add information on the potential interaction of dark matter with ordinary matter. After three years of detector prototyping COSINUS is ready to construct its own experimental facility described in this conceptual design report.