Search

Abstract We report the measurement of the two-neutrino double-beta ($$2\nu \beta \beta $$ 2νββ ) decay of $$^{100}$$ 100 Mo to the ground state of $$^{100}$$ 100 Ru using lithium molybdate ($$\hbox {Li}_2^{\;\;100}\hbox {MoO}_4$$ Li2100MoO4 ) scintillating bolometers. The detectors were developed for the CUPID-Mo program and operated at the EDELWEISS-III low background facility in the Modane underground laboratory (France). From a total exposure of 42.235 kg$$\times $$ × day, the half-life of $$^{100}$$ 100 Mo is determined to be $$T_{1/2}^{2\nu }=[7.12^{+0.18}_{-0.14}\,\mathrm {(stat.)}\pm 0.10\,\mathrm {(syst.)}]\times 10^{18}$$ T1/22ν=[7.12-0.14+0.18(stat.)±0.10(syst.)]×1018 years. This is the most accurate determination of the $$2\nu \beta \beta $$ 2νββ half-life of $$^{100}$$ 100 Mo to date.

Abstract CUPID-Mo is a bolometric experiment to search for neutrinoless double-beta decay ($$0\nu \beta \beta $$ 0νββ ) of $$^{100}\hbox {Mo}$$ 100Mo . In this article, we detail the CUPID-Mo detector concept, assembly and installation in the Modane underground laboratory, providing results from the first datasets. The CUPID-Mo detector consists of an array of 20 $$^{100}\hbox {Mo}$$ 100Mo -enriched 0.2 kg $$\hbox {Li}_2\hbox {MoO}_4$$ Li2MoO4 crystals operated as scintillating bolometers at $$\sim 20\hbox { mK}$$ ∼20mK . The $$\hbox {Li}_2\hbox {MoO}_4$$ Li2MoO4 crystals are complemented by 20 thin Ge optical bolometers to reject $$\alpha $$ α events by the simultaneous detection of heat and scintillation light. We observe a good detector uniformity and an excellent energy resolution of 5.3 keV (6.5 keV) FWHM at 2615 keV, in calibration (physics) data. Light collection ensures the rejection of $$\alpha $$ α particles at a level much higher than 99.9% – with equally high acceptance for $$\gamma $$ γ /$$\beta $$ β events – in the region of interest for $$^{100}\hbox {Mo}$$ 100Mo $$0\nu \beta \beta $$ 0νββ . We present limits on the crystals’ radiopurity: $$\le 3~\mu \hbox {Bq/kg}$$ ≤3μBq/kg of $$^{226}\hbox {Ra}$$ 226Ra and $$\le 2~\mu \hbox {Bq/kg}$$ ≤2μBq/kg of $$^{232}\hbox {Th}$$ 232Th . We discuss the science reach of CUPID-Mo, which can set the most stringent half-life limit on the $$^{100}\hbox {Mo}$$ 100Mo $$0\nu \beta \beta $$ 0νββ decay in half-a-year’s livetime. The achieved results show that CUPID-Mo is a successful demonstrator of the technology developed by the LUMINEU project and subsequently selected for the CUPID experiment, a proposed follow-up of CUORE, the currently running first tonne-scale bolometric $$0\nu \beta \beta $$ 0νββ experiment.