Direct Dark Matter Search with CRESST: Quenching Factor Measurements of CaWO4 at mK Temperatures and Detector Prototypes.

• Raimund Strauß (TUM)

Room: Main-2-313 Abstract: In this talk I will present the results obtained during my PhD thesis in the framework of direct Dark Matter search with the CRESST experiment. At the accelerator of the Maier-Leibnitz Laboratorium in Garching a dedicated neutron-scattering facility was set up to measure light-quenching factors (QFs) under realistic measurement conditions in a running CRESST-like detector module. The QFs of CaWO4 - in particular that of the heavy element W (A=184) - were measured with unprecedented accuracy at mK temperatures and for the first time a clear energy dependence could be observed. These results describe the data of CRESST detector modules well and influence the Dark Matter analysis considerably. Furthermore, detector prototypes which allow to reduce the background level in CRESST detectors significantly were developed and investigated in a series of measurements in the test cryostat at Gran Sasso. The highlights of these studies will be presented, in particular the development of a novel fully-scintillating detector design based on CaWO4 sticks of which two modules have been implemented into the CRESST setup for the upcoming run. These efforts should lead to a highly-efficient suppression of surface backgrounds and help to clarify in the near future whether the observed signal excess in the last CRESST run (run32) was due to unconsidered backgrounds or a true hint for Dark Matter of the low-mass WIMP type. In my conclusions I will discuss the present status of direct Dark Matter detection and the near-time perspective of the CRESST experiment.

Recent Results from CDMS II, Status and Future of the SuperCDMS Experiment

• Silvia Scorza (Southern Methodist University, Dallas)

Room: Main-2-313 Abstract: The CDMS II collaboration operated an experiment consisting of cryogenic Ge and Si detectors designed for the direct detection of Weakly Interacting Massive Particle (WIMPs) dark matter from 2003 - 2008. Currently the SuperCDMS collaboration is operating ~9 kg of advanced iZIP germanium detectors with larger mass and improved background discrimination in the CDMS II cryostat. In this talk I will discuss the latest results from the CDMS II experiment and present the current status and plans of the new SuperCDMS experiment.

Background Suppression with CRESST-II:

• Sabine Roth (TUM)

Room: Main-1-104 The dark matter search experiment CRESST-II (Cryogenic Rare Event Search with Super- conducting Thermometers) aims at the direct detection of WIMPs (Weakly Interacting Massive Particles) which are candidates to account for the non-baryonic Dark Matter content in our universe. The CRESST-II detector uses cryogenic phonon-light detector- modules with CaWO4 as target material to achieve the required event-by-event background suppression for the rare event search. The efficiency of this background-suppression tech- nique is based on the performance of the light detector as well as on the knowledge and understanding of the differing light-quenching effect observed for different interacting par- ticles in CaWO4. In my talk, I will first address different possibilities that were investigated in order to improve and understand the background-suppression capability of CRESST detector mo- dules. Experimental results obtained with a cryogenic light detector built according to the so-called composite detector design as well as with a Neganov-Luke amplified light detector are presented. The potential of these two techniques to optimize the background- suppression capability of CRESST detector modules is discussed. In the second part of my talk, a comprehensive microscopic model developed to explain the light generation and the light-quenching effect observed for different interacting particles in CaWO4 will be presented. This model not only predicts the different amounts of scin- tillation light generated for different interacting particles, but also allows to calculate the decay-time spectrum of the scintillation light. Thus, it has been possible to determine the free model parameters and to validate the model independently of the produced amount of scintillation light. With this model, quenching factors for different particle energies and for different temperatures and defect concentrations of the CaWO4 crystal were calculated. The results will be described.