Rejection of randomly coinciding events in Li 2100MoO4 scintillating bolometers using light detectors based on the Neganov–Luke effect

Random coincidences of nuclear events can be one of the main background sources in low-temperature calorimetric experiments looking for neutrinoless double-beta decay, especially in those searches based on scintillating bolometers embedding the promising double-beta candidate 100 Mo, because of the relatively short half-life of the two-neutrino double-beta decay of this nucleus. We show in this work that randomly coinciding events of the two-neutrino double-beta decay of 100 Mo in enriched Li2100MoO4 detectors can be effectively discriminated by pulse-shape analysis in the light channel if the scintillating bolometer is provided with a Neganov–Luke light detector, which can improve the signal-to-noise ratio by a large factor, assumed here at the level of ∼ 750 on the basis of preliminary experimental results obtained with these devices. The achieved pile-up rejection efficiency results in a very low contribution, of the order of ∼ 6 × 10 - 5 counts/(keV· kg· y), to the background counting rate in the region of interest for a large volume (∼ 90 cm3) Li2100MoO4 detector. This background level is very encouraging in view of a possible use of the Li2100MoO4 solution for a bolometric tonne-scale next-generation experiment as that proposed in the CUPID project.