New measurement of double-β decays of 100Mo to excited states of 100Ru with the CUPID-Mo experiment

The CUPID-Mo experiment, located at the Laboratoire Souterrain de Modane (France), was a demonstrator experiment for CUPID. It consisted of an array of 20Li2100MoO4 (LMO) calorimeters, each equipped with a Ge light detector for particle identification. In this work, we present the result of a search for two-neutrino and neutrinoless double-β decays of 100Mo to the first 0+ and 2+ excited states of 100Ru using the full CUPID-Mo exposure (2.71kgyr of LMO). We measure the half-life of 2νββ decay to the 0+1 state as T2ν→0+11/2=(7.5±0.8(stat.)+0.4−0.3(syst.))×1020yr. The bolometric technique enables measurement of the electron energies as well as the γ rays from nuclear deexcitation and this allows us to set new limits on the two-neutrino decay to the 2+1 state of T2ν→2+11/2>4.4×1021yr(90% c.i.) and on the neutrinoless modes of T0ν→2+11/2>2.1×1023yr(90% c.i.), T0ν→0+11/2>1.2×1023yr(90% c.i.). Information on the electrons' spectral shape is obtained, which allows us to make the first comparison of the single and higher state dominance 2νββ decay models for the 0+1 excited state of 100Ru.peerReviewe