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We report on the measurement of the two-neutrino double-beta decay half-life of [Formula omitted]Te with the CUORE-0 detector. From an exposure of 33.4 kg year of TeO [Formula omitted], the half-life is determined to be [Formula omitted] = [8.2 ± 0.2 (stat.) ± 0.6 (syst.)] [Formula omitted] 10 [Formula omitted] year. This result is obtained after a detailed reconstruction of the sources responsible for the CUORE-0 counting rate, with a specific study of those contributing to the [Formula omitted]Te neutrinoless double-beta decay region of interest.

The CUORE detector will be made of 988 TeO 2 crystals and will need a base temperature lower than 10 mK in order to meet the performance specifications. To cool the CUORE detector a large cryogen-free cryostat with five pulse tubes and one specially designed high-power dilution refrigerator has been designed. The detector assembly has a total mass of about 1.5 ton and uses a vibration decoupling suspension system. Because of the stringent requirements regarding radioactivity, about 12 tons of lead shielding need to be cooled to 4 K and below, and only a limited number of construction materials are acceptable. The eight retractable radioactive sources for detector calibration and about 2600 signal wires add further complexity to the system. The many stringent and contrasting requirements together with the overall large size made the design of the CUORE cryogenic system a real mechanical and cryogenic engineering challenge. The cryogenic system is expected to be fully operational in the Gran Sasso Laboratory in July 2013. We report here about the current status of the cryogenic system construction, which has started about one year.

We present precise measurements of the resistance-temperature variation of several samples of neutron transmutation doped (NTD) germanium, at temperatures from 70 mK to 1 K. This material is widely used for sensitive thermometry, often as the thermistor element in bolometers and microcalorimeters. It is also used in investigations of the low temperature conductivity of highly doped semiconductors. The resistance, R, is expected to follow the variable range hopping equation R(T)=R0 exp(T0/T)p, where T is temperature and R0 and T0 are material parameters. A value of p=0.5 is predicted theoretically, and generally seems to be in good agreement with experimental measurements. However, some theories and numerical calculations predict different values of p. Knowledge of the correct resistance-temperature relationship is important for the accurate calibration of thermometers, and also delivers insight into the basic physics involved. Most experimental measurements on germanium have not had sufficient precision to distinguish between the different predicted values of p. We show that such measurements are nevertheless possible. Our results are all in excellent agreement with the expected variable range hopping behaviour. However, the values of p appear to vary with doping density, in disagreement with most theories. We have considered and rejected both random and systematic errors as an explanation for the observed behaviour, and have confirmed the results by making measurements in two different systems with independent readout systems and temperature calibrations. The situation is complicated by the possibility of temperature dependence of R0. The expected form is R0(T)∝Tq; however, there is considerable disagreement over the predicted value of q. We show that in general it is not possible to determine both p and q from resistance measurements. However, our results can only be explained if either or both of q and p vary from sample to sample. Such behaviour is not generally expected. We show that neglecting the q term can lead to serious errors when calibrating thermometers. However, the degeneracy between p and q means that for a calibration the q term can be neglected, and good fits obtained if p is allowed to vary. Our results suggest that further theoretical work is required in this area, backed up by more comprehensive measurements.

Neutrinoless double beta decay ( 0 ν β β ) is one of the most sensitive probes for physics beyond the Standard Model, providing unique information on the nature of neutrinos. In this paper we review the status and outlook for bolometric 0 ν β β  decay searches. We summarize recent advances in background suppression demonstrated using bolometers with simultaneous readout of heat and light signals. We simulate several configurations of a future CUORE-like bolometer array which would utilize these improvements and present the sensitivity reach of a hypothetical next-generation bolometric 0 ν β β  experiment. We demonstrate that a bolometric experiment with the isotope mass of about 1 ton is capable of reaching the sensitivity to the effective Majorana neutrino mass ( | m e e | ) of order 10–20 meV, thus completely exploring the so-called inverted neutrino mass hierarchy region. We highlight the main challenges and identify priorities for an R&D program addressing them.

Neutrinoless double-beta (0 ν β β ) decay is a hypothesized lepton-number-violating process that offers the only known means of asserting the possible Majorana nature of neutrino mass. The Cryogenic Underground Observatory for Rare Events (CUORE) is an upcoming experiment designed to search for 0 ν β β decay of 130Te using an array of 988 TeO2 crystal bolometers operated at 10 mK. The detector will contain 206 kg of 130Te and have an average energy resolution of 5 keV; the projected 0 ν β β decay half-life sensitivity after five years of livetime is 1.6 × 1026 y at 1 σ (9.5 × 1025 y at the 90% confidence level), which corresponds to an upper limit on the effective Majorana mass in the range 40–100 meV (50–130 meV). In this paper, we review the experimental techniques used in CUORE as well as its current status and anticipated physics reach.

We report a study of the CUORE sensitivity to neutrinoless double beta ( 0 ν β β ) decay. We used a Bayesian analysis based on a toy Monte Carlo (MC) approach to extract the exclusion sensitivity to the 0 ν β β decay half-life ( T 1 / 2 0 ν ) at 90 %  credibility interval (CI) – i.e. the interval containing the true value of T 1 / 2 0 ν with 90 % probability – and the 3 σ discovery sensitivity. We consider various background levels and energy resolutions, and describe the influence of the data division in subsets with different background levels. If the background level and the energy resolution meet the expectation, CUORE will reach a 90 %  CI exclusion sensitivity of 2 · 10 25  year with 3 months, and 9 · 10 25  year with 5 years of live time. Under the same conditions, the discovery sensitivity after 3 months and 5 years will be 7 · 10 24  year and 4 · 10 25  year, respectively.

Abstract We report a study of the CUORE sensitivity to neutrinoless double beta (0ν β β 0 ν β β ) decay. We used a Bayesian analysis based on a toy Monte Carlo (MC) approach to extract the exclusion sensitivity to the0ν β β 0 ν β β decay half-life (T_(1/2)^(0ν)T 1 / 2 0 ν ) at90%90 %  credibility interval (CI) – i.e. the interval containing the true value ofT_(1/2)^(0ν)T 1 / 2 0 ν with90%90 % probability – and the3 σ 3 σ discovery sensitivity. We consider various background levels and energy resolutions, and describe the influence of the data division in subsets with different background levels. If the background level and the energy resolution meet the expectation, CUORE will reach a90%90 %  CI exclusion sensitivity of2⋅ 10²⁵2 · 10 25  year with 3 months, and9⋅ 10²⁵9 · 10 25  year with 5 years of live time. Under the same conditions, the discovery sensitivity after 3 months and 5 years will be7⋅ 10²⁴7 · 10 24  year and4⋅ 10²⁵4 · 10 25  year, respectively.

The advantages of using liquid helium as the investigative fluid in Rayleigh-Bénard experiments are reviewed. A low temperature shadowgraphy apparatus is described that permits convective flow pattern visualisation in liquid helium, thus overcoming the main disadvantage until now of using quantum fluids. The factors involved in maximising the optical resolution for both the shadowgraph and schlieren methods are examined for several fluids and this discussion is applied to the low temperature apparatus in assessing its performance. Some preliminary results on pattern formation in liquid helium are presented.

We report on the measurement of the two-neutrino double-beta decay half-life of 130 Te with the CUORE-0 detector. From an exposure of 33.4 kg year of TeO 22 , the half-life is determined to be T$2ν\\atop{1/2}$ = [8.2 ± 0.2 (stat.) ± 0.6 (syst.)] ×× 10 20 year. This result is obtained after a detailed reconstruction of the sources responsible for the CUORE-0 counting rate, with a specific study of those contributing to the 130130 Te neutrinoless double-beta decay region of interest.