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arXiv · 1410.4188

Beta/gamma and alpha backgrounds in CRESST-II Phase 2

R. Strauss·G. Angloher·A. Bento·C. Bucci·L. Canonica·A. Erb·F. v. Feilitzsch·N. Ferreiro Iachellini·P. Gorla·A. Gütlein·D. Hauff·J. Jochum·M. Kiefer·H. Kluck·H. Kraus·J. -C. Lanfranchi·J. Loebell·A. Münster·F. Petricca·W. Potzel·F. Pröbst·F. Reindl·S. Roth·K. Rottler·C. Sailer·K. Schäffner·J. Schieck·S. Scholl·S. Schönert·W. Seidel·M. v. Sivers·L. Stodolsky·C. Strandhagen·A. Tanzke·M. Uffinger·A. Ulrich·I. Usherov·S. Wawoczny·M. Willers·M. Wüstrich·A. Zöller
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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 CaWO$_4$ crystal, called TUM40, grown at the Technische Universität München. 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 $3.08\pm0.04$ mBq/kg are the lowest reported for CaWO$_4$ 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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R. Strauss, G. Angloher, A. Bento, C. Bucci, L. Canonica, A. Erb, F. v. Feilitzsch, N. Ferreiro Iachellini, P. Gorla, A. Gütlein, D. Hauff, J. Jochum, M. Kiefer, H. Kluck, H. Kraus, J. -C. Lanfranchi, J. Loebell, A. Münster, F. Petricca, W. Potzel, F. Pröbst, F. Reindl, S. Roth, K. Rottler, C. Sailer, K. Schäffner, J. Schieck, S. Scholl, S. Schönert, W. Seidel, M. v. Sivers, L. Stodolsky, C. Strandhagen, A. Tanzke, M. Uffinger, A. Ulrich, I. Usherov, S. Wawoczny, M. Willers, M. Wüstrich, A. Zöller. 2016-01-25. Beta/gamma and alpha backgrounds in CRESST-II Phase 2. https://doi.org/10.1088/1475-7516%2F2015%2F06%2F030

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