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

This paper reports on the development of a technology involving $$ -enriched scintillating bolometers, compatible with the goals of CUPID, a proposed next-generation bolometric experiment to search for neutrinoless double-beta decay. Large mass ( $$ ), high optical quality, radiopure $$ -containing zinc and lithium molybdate crystals have been produced and used to develop high performance single detector modules based on 0.2-0.4 kg scintillating bolometers. In particular, the energy resolution of the lithium molybdate detectors near the Q-value of the double-beta transition of $$ (3034 keV) is 4-6 keV FWHM. The rejection of the $$ -induced dominant background above 2.6 MeV is better than $$ . Less than $$ activity of $$ and $$ in the crystals is ensured by boule recrystallization. The potential of $$ -enriched scintillating bolometers to perform high sensitivity double-beta decay searches has been demonstrated with only $$ exposure: the two neutrino double-beta decay half-life of $$ has been measured with the up-to-date highest accuracy as $$ = [6.90 ± 0.15(stat.) ± 0.37(syst.)] $$ . 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 $$ .