Final results on the 0νββ decay half-life limit of 100Mo from the CUPID-Mo experiment

Abstract

The CUPID-Mo experiment to search for 0$\nu \beta \beta$ decay in ${}^{100}$Mo has been recently completed after about 1.5 years of operation at Laboratoire Souterrain de Modane (France). It served as a demonstrator for CUPID, a next generation 0$\nu \beta \beta$ decay experiment. CUPID-Mo was comprised of 20 enriched ${\text{Li}}_2$${}^{100}$${\text{MoO}}_4$ scintillating calorimeters, each with a mass of $\sim 0.2$ kg, operated at $\sim 20$ mK. We present here the final analysis with the full exposure of CUPID-Mo (${}^{100}$Mo exposure of 1.47 $\text{kg}\times \text{year}$) used to search for lepton number violation via 0$\nu \beta \beta$ decay. We report on various analysis improvements since the previous result on a subset of data, reprocessing all data with these new techniques. We observe zero events in the region of interest and set a new limit on the ${}^{100}$Mo 0$\nu \beta \beta$ decay half-life of $T_{1/2}^{0\nu }$$>1.8\times {10}^{24}$ year (stat. + syst.) at 90% CI. Under the light Majorana neutrino exchange mechanism this corresponds to an effective Majorana neutrino mass of $〈m_{\beta \beta }〉$  $<(0.28-0.49)$ eV, dependent upon the nuclear matrix element utilized.