Rejection of randomly coinciding events in Li $$_2^{100}\mathrm{MoO}_4$$ 2 100 MoO 4 scintillating bolometers using light detectors based on the Neganov–Luke effect

Abstract

Random coincidences of nuclear events can be one of the main background sources in low-temperature calorimetric experiments looking for neutrinoless doublebeta 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 twoneutrino 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 Li 100 2 MoO 4 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 cm 3 ) Li 100 2 MoO 4 detector. This background level is very encouraging in view of a possible use of the Li 100 2 MoO 4 solution for a bolometric tonne-scale next-generation experiment as that proposed in the CUPID project.

Characterization of cubic Li$$_{2}$$$$^{100}$$MoO$$_4$$ crystals for the CUPID experiment

“…Light pulses are faster compared to heat pulses and thus could help disentangling two partly overlapped pulses. Improving the signal-to-noise ratio of such pulses would make the pile-up rejection more effective [85][86][87]; -tolerating the (potential) malfunctioning of one of the two light detectors coupled to the LMO crystals; -coping with a possible higher noise of some LD.…”

Scintillation in Low-Temperature Particle Detectors

“…The 2νDBD induced pile-ups are worrisome for 100 Mo-and 150 Nd-enriched LTDs due to considerably high 2νDBD rates of these isotopes (e.g., ∼20 mHz in 1 kg of 100 Mo), which are at least an order of magnitude faster than that of other 2νDBD-active nuclides [37]. This issue can largely be mitigated by a pulse-shape analysis of heat signals [205,206], while a further improvement in the pile-up-induced background reduction would be possible by the analysis of the faster scintillation light signals with enhanced signal-to-noise ratio [207].…”

Final results of CALDER: kinetic inductance light detectors to search for rare events

“…Nevertheless, the physics reach of CUPID (or other bolometric projects such as AMoRE [28]), could be largely increased with faster light detectors. Rise times of the order of hundreds of µs or below would allow to reject the ultimate envisioned background, consisting of pile-up events from the naturally occurring double-β decay with the emission of 2 neutrinos [29,30]. Furthermore, detectors offering multiplexing capabilities would allow to increase the number of devices without increasing the thermal load on the cryogenic facility, and ease of fabrication and low-cost readout are highly desirable features for large scale experiments.…”