Final Result on the Neutrinoless Double Beta Decay of 82Se with CUPID-0

CUPID-0, an array of Zn82Se cryogenic calorimeters, was the first medium-scale demonstrator of the scintillating bolometers' technology. The first project phase (March 2017-December 2018) allowed the most stringent limit on the neutrinoless double beta decay half-life of the isotope of interest, 82Se, to be set. After a six month long detector upgrade, CUPID-0 began its second and last phase (June 2019-February 2020). In this Letter, we describe the search for neutrinoless double beta decay of 82Se with a total exposure (phase I thorn II) of 8.82 kg yr-1 of isotope. We set a limit on the half-life of 82Se to the ground state of 82Kr of T0z/ 1/2(82Se) > 4.6 x 1024 yr (90% credible interval), corresponding to an effective Majorana neutrino mass m beta beta < (263-545) meV. We also set the most stringent lower limits on the neutrinoless decays of 82Se to the 0 thorn 1 , 2 thorn 1 , and 2 thorn 2 excited states of 82Kr, finding 1.8 x 1023 yr, 3.0 x 1023 yr, and 3.2 x 1023 yr (90% credible interval) respectively.

Automated summary

CUPID-0, a scintillating bolometers' technology demonstrator, was used to study the limits of neutrinoless double beta decay. Through a detector upgrade, the study successfully set limits on the half-life of 82Se and the neutrinoless decays of 82Se to different excited states of 82Kr.