Constraints on lepton number violation with the 2 tonne · year CUORE dataset.

Matter-antimatter asymmetry underlines the incompleteness of the current understanding of particle physics. Neutrinoless double-beta decay (0νββ) may help explain this asymmetry while unveiling the Majorana nature of the neutrino. The CUORE (Cryogenic Underground Observatory for Rare Events) experiment searches for 0νββ of 130Te using a tonne-scale cryogenic calorimeter operated at milli-kelvin temperatures. We report no evidence of 0νββ and place a lower limit on the half-life of T1/2 > 3.5 × 1025 years (90% credibility interval) with over 2 tonne·years of TeO2 exposure. The tools and techniques developed for this result and the 5-year stable operation of nearly 1000 detectors demonstrate crucial infrastructure for future-generation experiments capable of searching for 0νββ across multiple isotopes. Editor's summary: We live in a world with too much matter (as opposed to antimatter). One of the theories that can account for this imbalance posits that the lepton number is not conserved. A process that illustrates lepton number violation is the so-called neutrinoless double beta decay, in which two neutrons inside a nucleus turn into two protons and release two electrons but no neutrinos. The Cryogenic Underground Observatory for Rare Events (CUORE) collaboration searched for this decay in an isotope of tellurium using a system of 988 cryogenic calorimeters housed in an underground facility. Several years' worth of data yielded no statistically significant evidence of the decay, but Bucci et al. succeeded in improving the constraints on the half-life for this process. —Jelena Stajic [ABSTRACT FROM AUTHOR]