In May 2018, we reported the results of the search for neutrinoless β+EC decay of 120Te performed using the final CUORE-0 data release. We described a new analysis method for the simultaneous fit of signatures with different event topology, and of data subsets with different signal efficiency, obtaining a limit on the half-life of the decay of T1/2 > 1.6 × 1021 yr at 90% CI. Combining this with results from Cuoricino, a predecessor experiment, we obtained the strongest limit to date, corresponding to T1/2 > 2.7 × 1021 yr at 90% CI.
The shown plot represents the energy spectrum relative to the signature in which the total energy is entirely absorbed by a single crystal. The curve corresponds to the best fit minimal model, with the 0νβ+EC decay peak normalized to the 90% CI limit. The shaded area corresponds to a 10 keV region around the expected signal peak position.
C. Alduino et al. (CUORE Collaboration). Phys. Rev. C 97, 055502 (2018)