Neutrinoless Double-Beta Decay Searches with Enriched $^{116}\hbox {CdWO}_{{4}}$ Scintillating Bolometers
Résumé
Cadmium-116 is one of the favorable candidates for neutrinoless double-beta decay ($0\nu \beta \beta $) searches from both theoretical and experimental points of view, in particular thanks to the high energy of the decay (2813.49 keV), the possibility of the industrial enrichment in $^{116}\mathrm{Cd}$ and its use in the well-established production of cadmium tungstate crystal scintillators. In this work, we present low-temperature tests of two $0.6\ \mathrm{kg} \ ^{116}\hbox {CdWO}_{{4}}$ crystals enriched in $^{116}\mathrm{Cd}$ to $82\%$ as scintillating bolometers. These detectors were operated underground, with one at the Laboratoire Souterrain de Modane (LSM) in France and the second at the Laboratorio Subterraneo de Canfranc (LSC) in Spain. The two crystals are coupled to bolometric Ge light detectors in order to register the scintillation light. The double readout of heat and scintillation enables reduction in the background in the region of interest by discriminating between different populations of particles. The main goal of these tests is the study of the crystals’ radiopurity and the detectors’ performance. The achieved results are extremely promising, in particular, the detectors demonstrate a high energy resolution (11–16 keV FWHM at 2615 keV) and a high-efficiency discrimination of the alpha background ($\sim 20 \sigma $). These results, achieved for the first time with large mass enriched $^{116}\hbox {CdWO}_{{4}}$ crystals, demonstrate prospects of the bolometric technology for high-sensitivity searches of $^{116}\mathrm{Cd}0\nu \beta \beta $ decay.