Final result on the neutrinoless double beta decay of Se82 with CUPID-0

CUPID-0, an array of Zn82-Se 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, 82-Se, 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 82-Se with a total exposure (phase I+II) of 8.82 kg·yr⁻¹ of isotope. We set a limit on the half-life of 82-Se to the ground state of 82-Kr of T₀ν₁/₂(82-Se) > 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 82-Se to the 0₁⁺, 2₁⁺, and 2₂⁺ excited states of 82-Kr, finding 1.8 × 10²³ yr, 3.0 × 10²³ yr, and 3.2 × 10²³ yr (90% credible interval) respectively.