A flexible scintillation light apparatus for rare event searches

Compelling experimental evidences of neutrino oscillations and their implication that neutrinos are massive particles have given neutrinoless double beta decay (ββ0ν) a central role in astroparticle physics. In fact, the discovery of this elusive decay would be a major breakthrough, unveiling that neutrino and antineutrino are the same particle and that the lepton number is not conserved. It would also impact our efforts to establish the absolute neutrino mass scale and, ultimately, understand elementary particle interaction unification. All current experimental programs to search for ββ0ν are facing with the technical and financial challenge of increasing the experimental mass while maintaining incredibly low levels of spurious background. The new concept described in this paper could be the answer which combines all the features of an ideal experiment: energy resolution, low cost mass scalability, isotope choice flexibility and many powerful handles to make the background negligible. The proposed technology is based on the use of arrays of silicon detectors cooled to 120 K to optimize the collection of the scintillation light emitted by ultrapure crystals. It is shown that with a 54 kg array of natural CaMoO4 scintillation detectors of this type it is possible to yield a competitive sensitivity on the half-life of the ββ0ν of 100Mo as high as ∝1024 years in only 1 year of data taking. The same array made of 40CanatMoO4 scintillation detectors (to get rid of the continuous background coming from the two neutrino double beta decay of 48Ca)will instead be capable of achieving the remarkable sensitivity of ∝1025 years on the half-life of 100Mo ββ0ν in only 1 year of measurement. (orig.)