UC Berkeley

The CUORE experiment is a large bolometric array searching for the lepton number violating neutrino-less double beta decay (0 νββ) in the isotope 130Te. In this work we present the latest results on two searches for the double beta decay (DBD) of 130Te to the first 02+ excited state of 130Xe : the 0 νββ decay and the Standard Model-allowed two-neutrinos double beta decay (2 νββ). Both searches are based on a 372.5 kg× yr TeO2 exposure. The de-excitation gamma rays emitted by the excited Xe nucleus in the final state yield a unique signature, which can be searched for with low background by studying coincident events in two or more bolometers. The closely packed arrangement of the CUORE crystals constitutes a significant advantage in this regard. The median limit setting sensitivities at 90% Credible Interval (C.I.) of the given searches were estimated as S1/20ν=5.6×1024yr for the 0 νββ decay and S1/22ν=2.1×1024yr for the 2 νββ decay. No significant evidence for either of the decay modes was observed and a Bayesian lower bound at 90 % C.I. on the decay half lives is obtained as: (T1/2)02+0ν>5.9×1024yr for the 0 νββ mode and (T1/2)02+2ν>1.3×1024yr for the 2 νββ mode. These represent the most stringent limits on the DBD of 130Te to excited states and improve by a factor ∼ 5 the previous results on this process.