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

CUPID-0 is the first large array of scintillating Zn ${}^{82}$ Se cryogenic calorimeters (bolometers) implementing particle identification for the search of the neutrinoless double beta decay (0 $\nu \beta \beta$ ). The detector consists of 24 enriched Zn ${}^{82}$ Se bolometers for a total ${}^{82}$ Se mass of 5.28 kg and it has been taking data in the underground LNGS (Italy) since March 2017. In this article we show how the dual read-out provides a powerful tool for the $\alpha$ particles rejection. The simultaneous use of the heat and light information allows us to reduce the background down to (3.2 ${}_{-1.1}^{+1.3}$ )×10 ${}^{-3}$ counts/(keV kg year), an unprecedented level for cryogenic calorimeters. In a total exposure of 5.46 kg year Zn ${}^{82}$ Se we set the most stringent limit on the 0 $\nu \beta \beta$ decay ${}^{82}$ Se half-life $T_{1/2}^{0\nu }>4.0\times {10}^{24}$ year at 90% C.I.