Background identification in cryogenic calorimeters through alpha -alpha delayed coincidences

O Azzolini ,D Chiesa ,A Giuliani ,P Gorla ,E Previtali ,C Bucci ,S Nisi ,A Cruciani ,L Gironi ,O Cremonesi ,D Orlandi ,I Dafinei ,S Pirro ,M Beretta ,M Clemenza ,L Cardani ,S Capelli ,M Martinez ,C Brofferio ,S Di Domizio ,M Pallavicini ,P Carniti ,L Pagnanini ,M Biassoni ,A Puiu ,G Keppel ,F Ferroni ,L Pattavina ,M Nastasi ,N Casali ,A D’addabbo ,F Bellini ,C Gotti ,M Pavan ,K Schäffner ,S Pozzi ,J W Beeman ,C Tomei ,S.s Nagorny ,G Pessina ,M Vignati ,C Nones ,C Rusconi ,V Pettinacci ,A Zolotarova

doi:10.1140/epjc/s10052-021-09476-z

Abstract

Localization and modeling of radioactive contaminations is a challenge that ultra-low background experiments are constantly facing. These are fundamental steps both to extract scientific results and to further reduce the background of the detectors. Here we present an innovative technique based on the analysis of alpha -alpha delayed coincidences in {}^{232}Th and {}^{238}U decay chains, developed to investigate the contaminations of the ZnSe crystals in the CUPID-0 experiment. This method allows to disentangle surface and bulk contaminations of the detectors relying on the different probability to tag delayed coincidences as function of the alpha decay position.

Highlights

Experiments searching for rare events, such as neutrinoless double-beta (0νββ) decay [1], demand for a detailed background understanding in order to implement possible a e-mail: davide.chiesa@mib.infn.it b e-mail: lorenzo.pagnanini@lngs.infn.it c e-mail: stefano.pozzi@mib.infn.it reduction techniques and to collect crucial information for next-generation experiments [2]
The number of candidate parents (NP) values obtained after subtracting the expected background counts are reported in Table 3, with an uncertainty that takes into account the Poisson fluctuations
We presented an innovative analysis technique to study the background sources in cryogenic calorimeters relying on the time-correlation of α-decay sequences in 238U and 232Th chains

Summary

Introduction

Experiments searching for rare events, such as neutrinoless double-beta (0νββ) decay [1], demand for a detailed background understanding in order to implement possible a e-mail: davide.chiesa@mib.infn.it (corresponding author) b e-mail: lorenzo.pagnanini@lngs.infn.it c e-mail: stefano.pozzi@mib.infn.it reduction techniques and to collect crucial information for next-generation experiments [2]. Cryogenic calorimeters [3,4] developed to search for the 0νββ decay have already demonstrated how to use these techniques to understand and reduce the background. Thanks to the experience gained with the Cuoricino experiment [5], a new conceptual design was introduced for the detector holder, mitigating the background due to degraded-energy α-particles emitted by copper contaminations in the CUORE-0 experiment [6]. We reached a deeper understanding of the background and we further reduced it through scintillating calorimeters [9,10,11,12], which introduced the groundbreaking possibility to identify the interacting particles

Methods

Results

Conclusion