Scintillating double-beta-decay bolometers
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Proceedings of the 5th International Conference on NONACCELERATOR NEW PHYSICS Double-Beta Decay and Rare Processes
Scintillating Double-Beta-Decay Bolometers* S. Pirro1)** , J. W. Beeman2) , S. Capelli1) , M. Pavan1) , E. Previtali1) , and P. Gorla3) Received November 23, 2005
Abstract—We present the results obtained in the development of scintillating double-beta-decay bolometers. Several Mo and Cd based crystals were tested with the bolometric technique. The scintillation light was measured through a second independent bolometer. A 140-g CdWO4 crystal was run in a 417-h live time measurement. Thanks to the scintillation light, the α background is easily discriminated, resulting in zero counts above the 2615-keV γ line of 208 Tl. These results, combined with an extreme easy light detector operation, represent the first tangible proof demonstrating the feasibility of this kind of technique. PACS numbers : 29.40.Mc DOI: 10.1134/S1063778806120155
1. INTRODUCTION The evidence of a neutrino rest mass represents one of the most exciting discoveries in the field of particle physics. The discovery of the neutrinoless double-beta decay (0ν-DBD), however, will provide not only the ultimate answer about the nature (Dirac or Majorana) of the neutrino, but will also allow one to improve the sensitivity to the neutrino mass to a few meV. As pointed out very recently by the members of the APS Multidivisional Neutrino Study [1], DBD searches will play a central role in neutrino physics of the next decade. The use of the bolometric technique offers the unique possibility to investigate different DBD nuclei with a considerably high energy resolution, needed for future experiments. In the case of a scintillating bolometer, the double independent readout (heat and scintillation) will allow, thanks to the different scintillation quenching factor (QF) between α and γ, the suppression of the background events due to degraded α particles, the main source of background for bolometric 0ν-DBD experiments [2]. 2. ENVIRONMENTAL BACKGROUND The experimental signature of the 0ν-DBD is in principle very clear: a peak (at the Qββ value) in the two-electron summed energy spectrum. In spite of such characteristic imprint, the rarity of the process makes the identification very difficult. Such a signal ∗
The text was submitted by the authors in English. Dipartimento di Fisica dell’Universita` di Milano-Bicocca and INFN, Sezione di Milano, Italy. 2) Lawrence Berkeley National Laboratory, USA. 3) Laboratori Nazionali del Gran Sasso, Italy. ** E-mail: [email protected] 1)
has to be disentangled from a background due to natural radioactive decay chains, cosmogenic-induced activity, and man-made radioactivity, which deposit energy in the same region as the DBD, but at a faster rate. Consequently, the main task in 0ν-DBD searches is the natural background suppression using state-of-the-art ultralow background techniques and, hopefully, identifying the signal. There are different sources of background for DBD experiments that can be classified in four main
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