M. Wüstrich — Page 2

arXiv2015

Results on low mass WIMPs using an upgraded CRESST-II detector

The CRESST-II cryogenic dark matter search aims for the detection of WIMPs via elastic scattering off nuclei in CaWO$_4$ crystals. We present results from a low-threshold analysis of a single upgraded detector module. This module efficiently vetoes low energy backgrounds induced by $α$-decays on inner surfaces of the detector. With an exposure of \unit[29.35]{kg live days} collected in 2013 we set a limit on spin-independent WIMP-nucleon scattering which probes a new region of parameter space for WIMP masses below \unit[3]{GeV/c$^2$}, previously not covered in direct detection searches. A possible excess over background discussed for the previous CRESST-II phase 1 (from 2009 to 2011) is not confirmed.

astro-ph.CO↗

arXiv2014

Radiopurity of CaWO$_4$ Crystals for Direct Dark Matter Search with CRESST and EURECA

The direct dark matter search experiment CRESST uses scintillating CaWO$_4$ single crystals as targets for possible WIMP scatterings. An intrinsic radioactive contamination of the crystals as low as possible is crucial for the sensitivity of the detectors. In the past CaWO$_4$ crystals operated in CRESST were produced by institutes in Russia and the Ukraine. Since 2011 CaWO$_4$ crystals have also been grown at the crystal laboratory of the Technische Universität München (TUM) to better meet the requirements of CRESST and of the future tonne-scale multi-material experiment EURECA. The radiopurity of the raw materials and of first TUM-grown crystals was measured by ultra-low background $γ$-spectrometry. Two TUM-grown crystals were also operated as low-temperature detectors at a test setup in the Gran Sasso underground laboratory. These measurements were used to determine the crystals' intrinsic $α$-activities which were compared to those of crystals produced at other institutes. The total $α$-activities of TUM-grown crystals as low as 1.23 $\pm$ 0.06 mBq/kg were found to be significantly smaller than the activities of crystals grown at other institutes typically ranging between ~15 mBq/kg and ~35 mBq/kg.

astro-ph.IM↗