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Register a new userEvidence of Single State Dominance in the Two-Neutrino Double-$beta$ Decay of Se-82 with CUPID-0
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We report on the measurement of the two-neutrino double-$beta$ decay of $^{82}$Se performed for the first time with cryogenic calorimeters, in the framework of the CUPID-0~experiment. With an exposure of 9.95 kg$times$yr of Zn$^{82}$Se, we determine the two-neutrino double-$beta$ decay half-life of $^{82}$Se with an unprecedented precision level, $T_{1/2}^{2 u} = [8.60 pm 0.03 textrm{(stat.)}~^{+0.17}_{-0.10} textrm{(syst.)}] times 10^{19}~textrm{yr}$. The very high signal-to-background ratio, along with the detailed reconstruction of the background sources allowed us to identify the single state dominance as the underlying mechanism of such process, demonstrating that the higher state dominance hypothesis is disfavored at the level of 5.5 $sigma$.
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We report the result of the search for neutrinoless double beta decay of $^{82}$Se obtained with CUPID-0, the first large array of scintillating Zn$^{82}$Se cryogenic calorimeters implementing particle identification. We observe no signal in a 1.83 kg yr $^{82}$Se exposure and we set the most stringent lower limit on the onu $^{82}$Se half-life T$^{0 u}_{1/2}>$ 2.4$times mathrm{10}^{24}$ yr (90% credible interval), which corresponds to an effective Majorana neutrino mass m$_{betabeta} <$ (376-770) meV depending on the nuclear matrix element calculations. The heat-light readout provides a powerful tool for the rejection of al particles and allows to suppress the background in the region of interest down to (3.6$^{+1.9}_{-1.4}$)$times$10$^{-3}$ckky, an unprecedented level for this technique.
A convincing observation of neutrino-less double beta decay (0$ u$DBD) relies on the possibility of operating high energy-resolution detectors in background-free conditions. Scintillating cryogenic calorimeters are one of the most promising tools to fulfill the requirements for a next-generation experiment. Several steps have been taken to demonstrate the maturity of this technique, starting from the successful experience of CUPID-0. The CUPID-0 experiment demonstrated the complete rejection of the dominant alpha background measuring the lowest counting rate in the region of interest for this technique. Furthermore, the most stringent limit on the $^{82}$Se 0$ u$DBD was established running 26 ZnSe crystals during two years of continuous detector operation. In this contribution we present the final results of CUPID-0 Phase I including a detailed model of the background, the measurement of the $^{82}$Se 2$ u$DBD half-life and the evidence that this nuclear transition is single state dominated.
CUPID-0 is the first pilot experiment of CUPID, a next-generation project searching for neutrino-less double beta decay. In its first scientific run, CUPID-0 operated 26 ZnSe cryogenic calorimeters coupled to light detectors in the underground Laboratori Nazionali del Gran Sasso. In this work, we analyzed a ZnSe exposure of 11.34 kg$times$yr to search for the neutrino-less double beta decay of $^{70}$Zn and for the neutrino-less positron-emitting electron capture of $^{64}$Zn. We found no evidence for these decays and set 90$%$ credible interval limits of ${rm T}_{1/2}^{0 ubetabeta}(^{70}{rm Zn}) > 1.6 times 10^{21}$ yr and ${rm T}_{1/2}^{0 u EC beta+}(^{64}{rm Zn}) > 1.2 times 10^{22}$ yr, surpassing by almost two orders of magnitude the previous experimental results
Solar neutrinos interact within double-beta decay (BB) detectors and contribute to backgrounds for BB experiments. Background contributions due to solar neutrino interactions with BB nuclei of $^{82}$Se, $^{100}$Mo, and $^{150}$Nd are evaluated. They are shown to be significant for future high-sensitivity BB experiments that may search for Majorana neutrino masses in the inverted-hierarchy mass region. The impact of solar neutrino backgrounds and their reduction are discussed for future BB experiments.
We report on the measurement of the two-neutrino double beta decay half-life of $^{130}$Te with the CUORE-0 detector. From an exposure of 33.4 kg$cdot$y of TeO$_2$, the half-life is determined to be $T_{1/2}^{2 u}$ = [8.2 $pm$ 0.2 (stat.) $pm$ 0.6 (syst.)] $times$ 10$^{20}$y. This result is obtained after a detailed reconstruction of the sources responsible for the CUORE-0 counting rate, with a specific study of those contributing to the $^{130}$Te neutrinoless double beta decay region of interest.
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