Development of 100 Mo -containing scintillating bolometers for a high-sensitivity neutrinoless double-beta decay search

Abstract

This paper reports on the development of a technology involving ${}^{100}\text{Mo}$ -enriched scintillating bolometers, compatible with the goals of CUPID, a proposed next-generation bolometric experiment to search for neutrinoless double-beta decay. Large mass ( $\sim 1\text{kg}$ ), high optical quality, radiopure ${}^{100}\text{Mo}$ -containing zinc and lithium molybdate crystals have been produced and used to develop high performance single detector modules based on 0.2-0.4 kg scintillating bolometers. In particular, the energy resolution of the lithium molybdate detectors near the Q-value of the double-beta transition of ${}^{100}\text{Mo}$ (3034 keV) is 4-6 keV FWHM. The rejection of the $\alpha$ -induced dominant background above 2.6 MeV is better than $8\sigma$ . Less than $10\mu \text{Bq/kg}$ activity of ${}^{232}\text{Th}{(}^{228}\text{Th})$ and ${}^{226}\text{Ra}$ in the crystals is ensured by boule recrystallization. The potential of ${}^{100}\text{Mo}$ -enriched scintillating bolometers to perform high sensitivity double-beta decay searches has been demonstrated with only $10\text{kg}\times \text{d}$ exposure: the two neutrino double-beta decay half-life of ${}^{100}\text{Mo}$ has been measured with the up-to-date highest accuracy as $T_{1/2}$ = [6.90 ± 0.15(stat.) ± 0.37(syst.)] $\times {10}^{18}\text{years}$ . Both crystallization and detector technologies favor lithium molybdate, which has been selected for the ongoing construction of the CUPID-0/Mo demonstrator, containing several kg of ${}^{100}\text{Mo}$ .