CUPID-0 is a ZnSe based experiment commissioned between the end of year 2016 and the beginning of 2017 at Laboratori Nazionali del Gran Sasso (LNGS). The detector is an array of 26 ZnSe crystals, 24 made with 82Se enriched material, operated as scintillating bolometers. It is the first ββ(0ν) experiment based on scintillating bolometers. Each crystal is instrumented to read-out both the phonon and the scintillation-photon signals produced by particle traversing its volume. Shape and amplitude of these signals are used to identify the interacting particle and measure its energy deposition. The phonon signal drives the determination of the energy, the light signal allows to discriminate highly ionizing particles like β/γ (including ββ(0ν) generated βs) from αs and nuclear recoils. The array is operated at about 10 mK in the Oxford Instrument dilution refrigerator formerly used by CUORE-0.
The realization of CUPID-0 is an important milestone made possible only after several years of R&D, pursued under the ERC LUCIFER grant (e qui il link alla vecchia pagina) that also funded the construction of the experiment.
The main physics goal of the experiment is the investigation of 82Se ββ(0ν) decay, signature of the decay is a monochromatic line in the phonon signal, equivalent to an energy deposition of 2998 keV in the crystal (the 82Se Q-value ). Exploiting the parti- cle discrimination capability of the detector, events with a similar energy deposition but produced by α particles can be rejected with high efficiency. The irreducible background will therefore derive from β/γ events, and is expected to be of the order of XXXX. If successful, CUPID-0 would open the way for a CUORE Upgrade with Particle Identification (CUPID).