160 research outputs found
Radiopure tungstate and molybdate crystal scintillators for double beta decay experiments
No full textInternational audienceCrystal scintillators are very promising detectors to investigate double beta decay of atomic nuclei. Recent achievements in development and application of tungstate and molybdate crystal scintillators, as well as prospects for the next generation double beta decay experiments are discussed
Potential of a next generation neutrinoless double beta decay experiment based on ZnMoO4 scintillating bolometers
No full textThe search for neutrinoless double β decay probes lepton number conservation with high sensitivity and investigates the neutrino nature and mass scale. Experiments presently in preparation will cover the quasi-degeneracy region of the neutrino mass pattern. Probing the socalled inverted hierarchy region requires improved sensitivities and next-generation experiments, based either on large expansions of the present searches or on new ideas. We examine here the potential of a novel technology relying on ZnMoO4 scintillating bolometers, which can provide an experiment with background close to zero in the ton × year exposure scale. The promising performance of a pilot detector is presented, both in terms of energy resolution and background control. A preliminary study of the sensitivities of future experiments shows that the inverted hierarchy region is within the reach of the technique here proposed. A realistic phased approach program towards a next-generation search is presented and briefly discussed
A multi-isotope bolometric experiment
No full textInternational audienceThere are valuable arguments to perform neutrinoless double beta ( ) decay experiments with several nuclei: the uncertainty of nuclear-matrix-element calculations, the possibility to test these calculations by using the ratio of the measured lifetimes, the unpredictability of possible breakthroughs in the detection technique, the difficulty to foresee background in decay searches, the limited amount of isotopically enriched materials. We propose therefore approaches to estimate the Majorana neutrino mass by combining experimental data collected with different decay candidates. In particular, we apply our methods to a next-generation experiment based on scintillating and Cherenkov-radiation bolometers. Current results indicate that this technology can effectively study up to four different isotopes simultaneously ( Se, Mo, Cd and Te), embedded in detectors which share the same concepts and environment. We show that the combined information on the Majorana neutrino mass extracted from a multi-candidate bolometric experiment is competitive with that achievable with a single isotope, once that the cryogenic experimental volume is fixed. The remarkable conceptual and technical advantages of a multi-isotope investigation are discussed. This approach can be naturally applied to the proposed CUPID project, follow-up of the CUORE experiment that is currently taking data in the Gran Sasso underground laboratory
Radioactive contamination of scintillators
No full textInternational audienceLow counting experiments (search for double β decay and dark matter particles, measurements of neutrino fluxes from different sources, search for hypothetical nuclear and subnuclear processes, low background α, β, γ spectrometry) require extremely low background of a detector. Scintillators are widely used to search for rare events both as conventional scintillation detectors and as cryogenic scintillating bolometers. Radioactive contamination of a scintillation material plays a key role to reach low level of background. Origin and nature of radioactive contamination of scintillators, experimental methods and results are reviewed. A programme to develop radiopure crystal scintillators for low counting experiments is discussed briefly
High sensitivity quest for Majorana neutrino mass with the BOREXINO counting test facility
No full textThe unique features of the CTF and BOREXINO set ups are used for a high sensitivity study of 100Mo and 116Cd neutrinoless 2β decay. Pilot measurements with 116Cd and Monte Carlo simulation show that the sensitivity of the CAMEO experiment (in terms of the T1/2 limit for 0ν2β decay) is (3–5) ×1024 yr with a 1 kg source of 100Mo (116Cd, 82Se, 150Nd) and ≈1026 yr with 65 kg of 116CdWO4 crystals placed in the CTF. The last value corresponds to a limit on the neutrino mass of mνless-than-or-equals, slant0.06 eV. Moreover, with 1000 kg of 116CdWO4 crystals located in the BOREXINO apparatus the neutrino mass limit can be pushed down to mνless-than-or-equals, slant0.02 eV
Has neutrinoless double β decay of 76Ge been really observed?
No full textAbstractThe claim of discovery of the neutrinoless double beta (0ν2β) decay of 76Ge [Mod. Phys. Lett. A 16 (2001) 2409] is considered critically and firm conclusion about, at least, prematurity of such a claim is derived on the basis of a simple statistical analysis of the measured spectra. This result is also proved by analyzing the cumulative data sets of the Heidelberg–Moscow and IGEX experiments. Besides, it allows us to establish the highest worldwide half-life limit on the 0ν2β decay of 76Ge: T1/20ν⩾2.5(4.2)×1025yrat90%(68%)C.L. This bound corresponds to the most stringent constraint on the Majorana neutrino mass: mν⩽0.3(0.2)eVat90%(68%)C.L
Rejection of randomly coinciding events in ZnMoO4 scintillating bolometers
No full textRandom coincidence of events (particularly from two neutrino double beta decay) could be one of the main sources of background in the search for neutrinoless double beta decay with cryogenic bolometers due to their poor time resolution. Pulse-shape discrimination by using front edge analysis, mean-time and χ2 methods were applied to discriminate randomly coinciding events in ZnMoO4 cryogenic scintillating bolometers. These events can be effectively rejected at the level of 99 % by the analysis of the heat signals with rise-time of about 14 ms and signal-to-noise ratio of 900, and at the level of 92 % by the analysis of the light signals with rise-time of about 3 ms and signal-to-noise ratio of 30, under the requirement to detect 95 % of single events. These rejection efficiencies are compatible with extremely low background levels in the region of interest of neutrinoless double beta decay of 100Mo for enriched ZnMoO4 detectors, of the order of 10-4 counts/(y keV kg). Pulse-shape parameters have been chosen on the basis of the performance of a real massive ZnMoO4 scintillating bolometer. Importance of the signal-to-noise ratio, correct finding of the signal start and choice of an appropriate sampling frequency are discussed
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