The CUPID-Mo experiment for neutrinoless double-beta decay: performance and prospects

Abstract

CUPID-Mo is a bolometric experiment to search for neutrinoless double-beta decay (0nu beta beta ) of ^{100}hbox {Mo}. 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}-enriched 0.2 kg hbox {Li}_2hbox {MoO}_4 crystals operated as scintillating bolometers at sim 20hbox { mK}. The hbox {Li}_2hbox {MoO}_4 crystals are complemented by 20 thin Ge optical bolometers to reject alpha 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 particles at a level much higher than 99.9% – with equally high acceptance for gamma /beta events – in the region of interest for ^{100}hbox {Mo}0nu beta beta . We present limits on the crystals’ radiopurity: le 3~mu hbox {Bq/kg} of ^{226}hbox {Ra} and le 2~mu hbox {Bq/kg} of ^{232}hbox {Th}. We discuss the science reach of CUPID-Mo, which can set the most stringent half-life limit on the ^{100}hbox {Mo}0nu beta beta 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 0nu beta beta experiment.