Simulation for the search of dark matter with CRESST

Over 80% of all matter in the universe is not visible, the so-called dark matter. This dark matter could be explained by introducing a new particle, which interacts weakly only with ordinary matter. However, to observe it, the interaction has to be stronger than the gravitational one. The predictions for the mass of this weakly interacting particle spans over several orders of magnitude. Recently, models with a mass range for dark matter particles between a few MeV and a few GeV have generated much interest. The CRESST experiment, which is currently being carried out at the Gran Sasso laboratory in Italy, is optimized for dark matter by searching for dark matter particles scattering with conventional matter. The energy of the scattering process is converted into lattice excitations of the detector crystal, the so-called phonons, and then read out with a sensor at the transition temperature. With the data collected so far by CRESST, no signal has been observed, however, the exclusion limits for dark matter candidates with a mass of less than 2 GeV are the best limit among the experiments for the direct search for dark matter. In the first funding period, the detection threshold for the recoil energy could be lowered down to 30 eV, an improvement of an order of magnitude compared to previous CRESST detectors and one of the lowest thresholds of all experiments. At recoil energies below 200 eV, however, the event rate rises sharply, and the origin of these energy deposits is not yet understood. Studies to identify these energy deposits are a central part of the project. These studies are based on detailed simulations studies and the analysis of experimental data. In addition to decoding this unknown background, different detector materials for the crystals, e.g., sapphire, are to be used in addition to the previously used detector material, calcium tungstate. These crystals and their properties must also be simulated to make full use of the data.