Pulse Shape Discrimination in CUPID-Mo using Principal Component Analysis

TL;DR

This paper demonstrates that principal component analysis can effectively discriminate between normal and anomalous pulse shapes in CUPID-Mo bolometers, improving background rejection in neutrinoless double-beta decay searches.

Contribution

The study introduces a data-driven PCA method for pulse shape discrimination in CUPID-Mo, eliminating the need for detector response simulations.

Findings

PCA successfully filters out anomalous events.

The method enhances background suppression capabilities.

It operates effectively without simulation dependence.

Abstract

CUPID-Mo is a cryogenic detector array designed to search for neutrinoless double-beta decay ($0\nu\beta\beta$) of $^{100}$Mo. It uses 20 scintillating $^{100}$Mo-enriched Li$_2$MoO$_4$ bolometers instrumented with Ge light detectors to perform active suppression of $\alpha$ backgrounds, drastically reducing the expected background in the $0\nu\beta\beta$ signal region. As a result, pileup events and small detector instabilities that mimic normal signals become non-negligible potential backgrounds. These types of events can in principle be eliminated based on their signal shapes, which are different from those of regular bolometric pulses. We show that a purely data-driven principal component analysis based approach is able to filter out these anomalous events, without the aid of detector response simulations.