Performances of a large mass ZnSe bolometer to search for rare events

TL;DR

This study evaluates a ZnSe bolometer's performance for rare event detection, focusing on background rejection, energy resolution, and nuclear recoil discrimination, crucial for neutrinoless double beta decay searches.

Contribution

It presents new measurements of scintillation yield, energy resolution, and nuclear recoil light emission in ZnSe bolometers, enhancing background discrimination techniques.

Findings

Improved alpha particle rejection with new analysis algorithm.

Achieved better energy resolution by combining heat and light signals.

Nuclear recoils emit negligible light, aiding WIMP detection.

Abstract

Scintillating bolometers of ZnSe are the baseline choice of the LUCIFER experiment, whose aim is to observe the neutrinoless double beta decay of 82Se. The independent read-out of the heat and scintillation signals allows to identify and reject alpha particle interactions, the dominant background source for bolometric detectors. In this paper we report the performances of a ZnSe crystal operated within the LUCIFER R&D. We measured the scintillation yield, the energy resolution and the background in the energy region where the signal from neutrinoless double beta decay of 82Se is expected with an exposure of 9.4 kg x days. With a newly developed analysis algorithm we improved the rejection of alpha events, and we estimated the increase in energy resolution obtained by the combination of the heat and light signals. For the first time we measured the light emitted by nuclear recoils, and found it to be compatible with zero. We conclude that the discrimination of nuclear recoils from beta/gamma interactions in the WIMPs energy region is possible, but low-noise light detectors are needed.