Cryogenic bolometer crystals for rare event searches⋆

Bolometers are suitable detectors for fundamental physics experiments, like neutrinoless Double Beta Decay, because of their very good intrinsic characteristics (high detection efficiency, excellent energy resolution, ...). The bolometric technique has already obtained excellent results on the neutrino mass study with Cuoricino, the ancestor of CUORE, an array of 19 towers with 52 crystals each, which will achieve a sensitivity below 100meV. Cuoricino has also shown that the surface contaminations of materials facing the detectors would be the limiting factor for the sensitivity of next-generation experiments with bolometers. Mainly for this reason scintillating bolometers have been developed allowing a very efficient discrimination of alpha particles thanks to their double readout. Excellent results were obtained with different compounds such as CdWO4 , ZnSe and ZnMoO4. Tests performed on these crystals showed the possibility to discriminate the interacting particles through a pulse shape analysis. This feature is very interesting because it allows to obtain the same (or even better) discrimination power achieved with the double readout but with a much easier and cheaper assembly. Finally, the sensitivity that could be achieved with a large mass array of scintillating bolometers is analyzed on the basis of the results obtained on background and energy resolution.