Final Result on the Neutrinoless Double Beta Decay of Se82 with CUPID-0

CUPID-0, an array of ZnSe82 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, Se82 , 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 Se82 with a total exposure (phase I +II ) of 8.82 kg yr−1 of isotope. We set a limit on the half-life of Se82 to the ground state of Kr82 of T 1 / 20ν ( Se82 ) >4.6×1024 yr (90% credible interval), corresponding to an effective Majorana neutrino mass mββ< ( 263–545 ) meV . We also set the most stringent lower limits on the neutrinoless decays of Se82 to the 01+ , 21+ , and 22+ excited states of Kr82 , finding 1.8×1023 yr , 3.0×1023 yr , and 3.2×1023 yr (90% credible interval) respectively.