Advanced search for neutrinoless double beta decay in selenium-82 with CUPID-0

The CUPID-0 detector hosted at the Laboratori Nazionali del Gran Sasso (LNGS), is the first large array of enriched scintillating cryogenic detectors for the investigation of 82Se neutrinoless double-beta decay (0⌫). The assembly of the experiment ended in October 2016 and after four months of commissioning, debugging and performance optimization the data taking has started in March 2017. No evidence of signal was found in a 1.83 kg · y 82Se exposure, setting the best lower limit on the 0⌫ 82Se half-life T0⌫ 1/2 >2.4 · 1024 y (90% C.I.), which corresponds to an effective Majorana neutrino mass m < 376-770 meV depending on the nuclear matrix element calculations. The heat-light readout provided a powerful tool for ↵- particles rejection and allowed to suppress the background in the region of interest to (3.6+1.9 1.4) · 103 counts/(keV · kg · y), an unprecedented level for this technique. This result was achieved by a forefront technology for background suppression and thorough protocols and procedures for detector preparation. This Ph.D. work describes all the different phases of the detector design, construction and optimization carried out at LNGS since February 2015. Moreover the analysis tasks such us pulse shape analysis, evaluation of internal contamination and eventually the fit in the region of interest are discussed.