The experiment CRESST`-II aims at the detection of dark matter with scintillating CaWO 4 crystals operated as cryogenic detectors. Recent results on spin-independent WIMP-nucleon scattering from the CRESST`-II Phase 2 allowed to probe a new region of parameter space for WIMP masses below 3 GeV/c(2). This sensitivity was achieved after background levels were reduced significantly. We present extensive background studies of a CaWO4 crystal, called TUM40, grown at the Technische Universitat Munchen. The average beta/gamma rate of 3.51/[kg keV day] (1-40 keV) and the total intrinsic alpha activity from natural decay chains of 3.08 +/- 0.04 mBq/kg are the lowest reported for CaWO4 detectors. Contributions from cosmogenic activation, surface-alpha decays, external radiation and intrinsic alpha/beta emitters are investigated in detail. A Monte-Carlo based background decomposition allows to identify the origin of the majority of beta/gamma events in the energy region relevant for dark matter search.
Strauss, R., Angloher, G., Bento, A., Bucci, C., Canonica, L., Erb, A., et al. (2015). Beta/gamma and alpha backgrounds in CRESST-II Phase 2. JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS, 2015(6) [10.1088/1475-7516/2015/06/030].
Beta/gamma and alpha backgrounds in CRESST-II Phase 2
Canonica L;
2015
Abstract
The experiment CRESST`-II aims at the detection of dark matter with scintillating CaWO 4 crystals operated as cryogenic detectors. Recent results on spin-independent WIMP-nucleon scattering from the CRESST`-II Phase 2 allowed to probe a new region of parameter space for WIMP masses below 3 GeV/c(2). This sensitivity was achieved after background levels were reduced significantly. We present extensive background studies of a CaWO4 crystal, called TUM40, grown at the Technische Universitat Munchen. The average beta/gamma rate of 3.51/[kg keV day] (1-40 keV) and the total intrinsic alpha activity from natural decay chains of 3.08 +/- 0.04 mBq/kg are the lowest reported for CaWO4 detectors. Contributions from cosmogenic activation, surface-alpha decays, external radiation and intrinsic alpha/beta emitters are investigated in detail. A Monte-Carlo based background decomposition allows to identify the origin of the majority of beta/gamma events in the energy region relevant for dark matter search.
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