Pulse Shape Discrimination in CUPID-Mo using Principal Component Analysis

Author(s): Huang, R; Armengaud, E; Augier, C; Barabash, AS; Bellini, F; Benato, G; Benoit, A; Beretta, M; Berge, L; Billard, J; Borovlev, Yu A; Bourgeois, Ch; Brudanin, VB; Camus, P; Cardani, L; Casali, N; Cazes, A; Chapellier, M; Charlieux, F; Combarieu, M de; Dafinei, I; Danevich, FA; Jesus, M De; Dixon, T; Dumoulin, L; Eitel, K; Ferri, F; Fujikawa, BK; Gascon, J; Gironi, L; Giuliani, A; Grigorieva, VD; Gros, M; Guerard, E; Helis, DL; Huang, HZ; Johnston, J; Juillard, A; Khalife, H; Kleifges, M; Kobychev, VV; Kolomensky, Yu G; Konovalov, SI; Loaiza, P; Ma, L; Makarov, EP; Marcillac, P de; Mariam, R; Marini, L; Marnieros, S; Misiak, D; Navick, X-F; Nones, C; Olivieri, E; Ouellet, JL; Pagnanini, L; Pari, P; Pattavina, L; Paul, B; Pavan, M; Peng, H; Pessina, G; Pirro, S; Poda, DV; Polischuk, OG; Previtali, E; Redon, Th; Rozov, S; Rusconi, C; Sanglard, V; Schaffner, K; Schmidt, B; Shen, Y; Shlegel, VN; Siebenborn, B; Singh, V; Tomei, C; Tretyak, VI; Umatov, VI; Vagneron, L; Velazquez, M; Weber, M; Welliver, B; Winslow, L; Xue, M | 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.