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 1.3 kg 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 ∼300 keV. The half-life extracted from the data is T1/22ν = [7.15 ± 0.37 (stat) ± 0.66 (syst)] × 1018 y. (paper)