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

TL;DR

This paper demonstrates that using Neganov-Luke light detectors with Li$_2$$^{100}$MoO$_4$ scintillating bolometers significantly reduces background noise from random coincidences of double-beta decay events, enhancing the sensitivity of neutrinoless double-beta decay searches.

Contribution

The study introduces a pulse-shape analysis method combined with Neganov-Luke light detectors to effectively discriminate against coincident background events in bolometric detectors for double-beta decay.

Findings

Achieved a pile-up rejection efficiency of ~99.994%

Reduced background contribution to ~6×10^{-5} counts/(keV·kg·y)

Demonstrated potential for large-scale neutrinoless double-beta decay experiments.

Abstract

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 decay of $^{100}$Mo in enriched Li$_2$$^{100}$MoO$_4$ detectors can be effectively discriminated by pulse-shape analysis in the light channel if the scintillating bolometer is provided with a Neganov-Luke light detector, which can improve the signal-to-noise ratio by a large factor, assumed here at the level of $\sim 750$ on the basis of preliminary experimental results obtained with these devices. The achieved pile-up rejection efficiency results in a very low contribution, of the order of $\sim 6\times10^{-5}$ counts/(keV$\cdot$kg$\cdot$y), to the background counting rate in the region of interest for a large volume ($\sim 90$ cm$^3$) Li$_2$$^{100}$MoO$_4$ detector. This background level is very encouraging in view of a possible use of the Li$_2$$^{100}$MoO$_4$ solution for a bolometric tonne-scale next-generation experiment as that proposed in the CUPID project.