Internal Backgrounds in the Water Phase of SNO+

TL;DR

This paper discusses the measurement of internal radioactive backgrounds in the water phase of the SNO+ experiment, which is crucial for background reduction and physics analyses in neutrinoless double-beta decay searches.

Contribution

It presents in situ measurements of $^{214}$Bi and $^{208}$Tl in the water phase, providing data to improve background understanding and inform future phases.

Findings

Quantified levels of $^{214}$Bi and $^{208}$Tl in water

Data supports background modeling for $0 uetaeta$ searches

Informs preparation for scintillator fill

Abstract

SNO+ is a neutrinoless double-beta decay ($0\nu\beta\beta$) search experiment using 780 tonnes of tellurium-loaded liquid scintillator. The experiment is currently collecting data in the first of three planned phases, in which the detector is filled with ultrapure water. During this phase, the cleanliness of the water can be assayed using in situ measurements of $^{214}$Bi and $^{208}$Tl (daughter nuclei of $^{238}$U and $^{232}$Th, respectively). These results will both inform preparation for scintillator fill and support water phase physics analyses like the search for invisible nucleon decay modes.