First bolometric measurement of the two neutrino double beta decay of ¹⁰⁰Mo with a ZnMoO₄ crystals array

The large statistics collected during the operation of a ZnMoO₄ array, for a total exposure of 1.3kg day of ¹⁰⁰Mo, allowed the first bolometric observation of the two neutrino double beta decay of ¹⁰⁰Mo. The observed spectrum of each crystal was reconstructed taking into account the different background contributions due to environmental radioactivity and internal contamination. The analysis of coincidences between the crystals allowed the assignment of constraints to the intensity of the different background sources, resulting in a reconstruction of the measured spectrum down to an energy of ∼300keV. The half-life extracted from the data is T_1/2 ^2v= [7.15 ± 0.37 (stat) ± 0.66 (syst)] × 10¹⁸ y.