Abstract
The LUCIFER project aims at deploying the first array of enriched scintillating bolometers for the investigation of neutrinoless double-beta decay of ^{82}Se. The matrix which embeds the source is an array of ZnSe crystals, where enriched ^{82}Se is used as decay isotope. The radiopurity of the initial components employed for manufacturing crystals, that can be operated as bolometers, is crucial for achieving a null background level in the region of interest for double-beta decay investigations. In this work, we evaluated the radioactive content in 2.5 kg of 96.3 % enriched ^{82}Se metal, measured with a high-purity germanium detector at the Gran Sasso deep underground laboratory. The limits on internal contaminations of primordial decay chain elements of ^{232}Th, ^{238}U and ^{235}U are respectively: <61, <110 and <74 mu Bq/kg at 90 % C.L. The extremely low-background conditions in which the measurement was carried out and the high radiopurity of the ^{82}Se allowed us to establish the most stringent lower limits on the half-lives of the double-beta decay of ^{82}Se to 0^+_1, 2^+_2 and 2^+_1 excited states of ^{82}Kr of 3.4cdot 10^{22}, 1.3cdot 10^{22} and 1.0cdot 10^{22} y, respectively, with a 90 % C.L.
Highlights
The observation of neutrinoless double-beta decay (0νββ) would demonstrate lepton number violation, and at the same time it would necessarily imply that the neutrinos have a Majorana character
We report on the analysis of the radiopurity level of the ββ decay source for the Low underground cryogenic installation for elusive rates (LUCIFER) experiment [10], namely 96.3 % enriched 82Se metal, performed at the Gran Sasso Underground Laboratory (LNGS) of INFN, sited in Italy
Summary
The observation of neutrinoless double-beta decay (0νββ) would demonstrate lepton number violation, and at the same time it would necessarily imply that the neutrinos have a Majorana character. The standard model counterpart of the 0νββ decay, is the 2νββ decay It is the rarest nuclear weak process experimentally observed in dozen of nuclei with half-lives in the range of 1018–1022 y [1]. In 1990, the first publication on the potential to observe 2νββ decay to excited levels of daughter nuclei was reported [3]. Among the various techniques for material screening a very common one is γ -spectroscopy using high-purity germanium (HP-Ge) detectors, since they ensure a rather low background level, gain stability and high energy resolution Such detectors match exactly the needs for a high sensitivity investigation of ββ decay on excited levels of daughter nuclei, where single γ quanta or cascades are produced during the de-excitation. Thanks to the high purity of the sample, new results on the experimental investigation of ββ decay of 82Se to the excited states 0+1 , 2+1 and 2+2 of 82Kr are presented
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
