Measurement of the 2$\hat{I}½{\hat{I}}^2{\hat{I}}^2$ Decay Half-Life of Se-82 with the Global CUPID-0 Background Model

Abstract

We report on the results obtained with the global CUPID-0 background model, which combines the data collected in the two measurement campaigns for a total exposure of 8.82~kg$\times$yr of ${}^{82}$Se. We identify with improved precision the background sources within the 3 MeV energy region, where neutrinoless double ${\hat{I}}^2$-decay of ${}^{82}$Se and ${}^{100}$Mo is expected, making more solid the foundations for the background budget of the next-generation CUPID experiment. Relying on the excellent data reconstruction, we measure the two-neutrino double ${\hat{I}}^2$-decay half-life of ${}^{82}$Se with unprecedented accuracy: $T_{1/2}^{2\hat{I}½}=[8.69\pm 0.05\text{(stat.)}{}_{-0.06}^{+0.09}\text{(syst.)}]\times 10^{19}\text{yr}$.