Optimization of the first CUPID detector module

Abstract

CUPID will be a next generation experiment searching for the neutrinoless double $$\beta $$ β decay, whose discovery would establish the Majorana nature of the neutrino. Based on the experience achieved with the CUORE experiment, presently taking data at LNGS, CUPID aims to reach a background free environment by means of scintillating Li$$_{2}$$ 2 $$^{100}$$ 100 MoO$$_4$$ 4 crystals coupled to light detectors. Indeed, the simultaneous heat and light detection allows us to reject the dominant background of $$\alpha $$ α particles, as proven by the CUPID-0 and CUPID-Mo demonstrators. In this work we present the results of the first test of the CUPID baseline module. In particular, we propose a new optimized detector structure and light sensors design to enhance the engineering and the light collection, respectively. We characterized the heat detectors, achieving an energy resolution of (5.9 ± 0.2) keV FWHM at the Q-value of $$^{100}$$ 100 Mo (about 3034 keV). We studied the light collection of the baseline CUPID design with respect to an alternative configuration which features gravity-assisted light detectors’ mounting. In both cases we obtained an improvement in the light collection with respect to past measures and we validated the particle identification capability of the detector, which ensures an $$\alpha $$ α particle rejection higher than 99.9%, fully satisfying the requirements for CUPID.

Twelve-crystal prototype of Li2MoO4 scintillating bolometers for CUPID and CROSS experiments

“…An example of the distribution of the L/H parameter is shown in figure 8 (left). Similar light-to-heat ratios were obtained in more recent tests of cubic LMOs with the same size [61][62][63], and in the LUMINEU and CUPID-Mo experiments realized with cylindrical LMOs [48,51,53].…”

“…Despite some difference in detectors' sensitivity, we did not observe a difference in energy resolution between LMOs instrumented with standard size NTDs and the larger ones. Also, it is interesting to note that the resolution of the 2615 keV 𝛾 peak is much better than one can expect from the baseline noise values; typically a factor 2-3 difference is reported [48,51,[61][62][63]. Thus, a large part of the measured noise does not have a notable impact on the variation of the LMO thermal signal.…”

“…Cubic crystals have been selected for CUPID [45] as well for CROSS (Cryogenic Rare-event Observatory with Surface Sensitivity), a project to demonstrate the potential of metal-coated bolometers capable of particle identification of near surface interactions [54][55][56][57][58][59]. Several cubic lithium molybdate samples with a size of 45 × 45 × 45 mm each -produced following the LUMINEU crystals fabrication protocol [48,49,60] -have been recently operated by CROSS and CUPID collaborations at the Canfranc underground laboratory (LSC) in Spain [61], and at the LNGS [62,63]. The results of these tests confirm LU-MINEU and CUPID-Mo findings on high energy resolution, high crystal radiopurity, and an efficient scintillation-assisted particle identification despite the modest light output of the material [33,48,51].…”

Impact of nuclear matrix element calculations for current and future neutrinoless double beta decay searches

“…There is a rich landscape of experiments proposed or in preparation exploiting different ββ emitters and experimental techniques. In particular, we consider LEGEND-1000 [49] for 76 Ge, SNO+II [50] for 130 Te, nEXO [51] for 136 Xe , SuperNEMO [52] for 82 Se and CUPID [53] for 100 Mo. Each of them is characterized by a set of so called performance parameters, through which both Table 4: Performance parameters assumed here for different next-generation 0νββ experiments [2] and PSF of the respective isotope [11].…”

Final results on the $$0\nu \beta \beta $$ decay half-life limit of $$^{100}$$Mo from the CUPID-Mo experiment

“…We process our data using the C++ softwares Apollo and Diana [37,38], first developed for the CUORE experiment and also used by CUORICINO, CUPID-0 and CUPID [39].…”