Karoline Schäffner, MPI for Physics: Low-temperature detectors for unveiling the nature of dark matter

Abstract: A direct detection of dark matter particles and possibly of new fundamental forces will revolutionize our understanding of the most basic building blocks of nature.Direct Dark Matter search programs cover particle masses from TeV/c₂ down to MeV/c₂ at present but do not provide an uncontroversial signal. In the low-mass regime, low-temperature detectors have demonstrated the required performance and keep exploring new regions of parameter space; they are best suited to probe the existence of novel particles and theories. Searching for a direct dark matter signal above the detector background includes looking for an annual modulation signal caused by the seasonal variation of the Earth’s velocity with respect to the sun and, thus, the dark matter halo. The DAMA/LIBRA experiment, a pioneer using such modulation as DM signature, observes a modulated signal rate with a very high statistical significance, and period and phase matching the DM expectation.The DAMA/LIBRA results are in strong tension with the null results of most of the other direct dark matter searches. However, as of today, a material and model-independent unambiguous cross-check is still missing to unveil this long-term puzzle. With COSINUS we work on the optimization of a novel quantum sensor layout for sodium iodide-based low-temperature detectors to perform a model-independent cross-check of the controversial Dark Matter claim of DAMA/LIBRA. In this seminar, I will discuss the detection principle of low-temperature detector, the latest results from the COSINUS prototype detector, and the last steps of the commissioning towards starting the first physics data-taking campaign in 2025. Furthermore I will shine some light on possible future searches by capitalizing on this extremely sensitive sensor design to read out so far unusable target materials and to mitigate detector-related backgrounds (Low Energy Excess, LEE) that block progress in current low-mass DM searches. In this context also a discussion on properties of interesting future materials is given.