New direct limit on neutrinoless double beta decay half-life of $^{128}$Te with CUORE

TL;DR

This paper reports the first direct experimental limit on the neutrinoless double beta decay half-life of $^{128}$Te, significantly improving previous results and surpassing geochemical measurements.

Contribution

It provides the most stringent direct limit on $^{128}$Te neutrinoless double beta decay half-life, using CUORE's low-background, large-mass detector.

Findings

No evidence for $^{128}$Te 0νββ decay was observed.

Lower limit on half-life set at >3.6×10^{24} years (90% CI).

Result surpasses previous direct and geochemical limits.

Abstract

The Cryogenic Underground Observatory for Rare Events (CUORE) at Laboratori Nazionali del Gran Sasso of INFN in Italy is an experiment searching for neutrinoless double beta (0$\nu\beta\beta$) decay. Its main goal is to investigate this decay in $^{130}$Te, but its ton-scale mass and low background make CUORE sensitive to other rare processes as well. In this work, we present our first results on the search for \nbb decay of $^{128}$Te, the Te isotope with the second highest natural isotopic abundance. We find no evidence for this decay, and using a Bayesian analysis we set a lower limit on the $^{128}$Te \nbb decay half-life of T$_{1/2} > 3.6 \times 10^{24}$ yr (90\% CI). This represents the most stringent limit on the half-life of this isotope, improving by over a factor 30 the previous direct search results, and exceeding those from geochemical experiments for the first time.