Search for Majoron-like particles with CUPID-0

We present the first search for the Majoron-emitting modes of the neutrinoless double decay (0₀) using scintillating cryogenic calorimeters. We analyzed the CUPID-0 Phase I data using a Bayesian approach to reconstruct the background sources activities, and evaluate the potential contribution of the ^82Se 0₀. We considered several possible theoretical models which predict the existence of a Majoron-like boson coupling to the neutrino. The energy spectra arising from the emission of such bosons in the neutrinoless double decay have spectral indices n=1, 2, 3, or 7. We found no evidence of any of these decay modes, setting a lower limit (90% of credibility interval) on the half-life of 1. 210^23 yr in the case of n=1, 3. 810^22 yr for n=2, 1. 410^22 yr for n=3 and 2. 210^21 yr for n=7. These are the best limits on the 0₀ half-life of the ^82Se, and demonstrate the potentiality of the CUPID-0 technology in this field.