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The Cryogenic Underground Observatory for Rare Events (CUORE) is a bolometric experiment for neutrinoless double-beta decay in 130 Te search, currently taking data at the underground facility of Laboratori Nazionali del Gran Sasso (LNGS). The CUORE cryostat successfully cooled down a mass of about 1 ton at ∼ 7 mK , delivering a uniform and constant base temperature. This result marks a fundamental milestone in low-temperature detector techniques, opening the path for future ton-scale bolometric experiments searching for rare events. In this paper, we present the CUORE cryogenic infrastructure, briefly describing its critical subsystems.

The Cryogenic Underground Observatory for Rare Events (CUORE) will search for the 0vββ decay in 130Te using a cryogenic array of TeO2 bolometers, operated at a base temperature of ~10mK. CUORE will consist of a closely packed array of 19 towers each containing 52 crystals, for a total mass of 741kg. The detector assembly is hosted in one of the largest cryostats ever constructed and will be cooled down to base temperature using a custom-built cryogen free dilution refrigerator. The CUORE cryostat along with the pulse tube based dilution refrigerator has been already commissioned at Laboratori Nazionali del Gran Sasso (LNGS) and a record base temperature, on a cubic meter scale, of ~6mK was achieved during one of the integration runs. We present the results from integration runs, characterizing the system and the cooling performance of the dilution refrigerator, effectively showcasing its stability at base temperature for the expected thermal load.

P-type point contact (PPC) HPGe detectors are a leading technology for rare event searches due to their excellent energy resolution, low thresholds, and multi-site event rejection capabilities. We have characterized a PPC detector’s response to α particles incident on the sensitive passivated and p+ surfaces, a previously poorly-understood source of background. The detector studied is identical to those in the MajoranaDemonstrator experiment, a search for neutrinoless double-beta decay (0νββ) in 76Ge. α decays on most of the passivated surface exhibit significant energy loss due to charge trapping, with waveforms exhibiting a delayed charge recovery (DCR) signature caused by the slow collection of a fraction of the trapped charge. The DCR is found to be complementary to existing methods of α identification, reliably identifying α background events on the passivated surface of the detector. We demonstrate effective rejection of all surface α events (to within statistical uncertainty) with a loss of only 0.2% of bulk events by combining the DCR discriminator with previously-used methods. The DCR discriminator has been used to reduce the background rate in the 0νββ region of interest window by an order of magnitude in the MajoranaDemonstrator and will be used in the upcoming LEGEND-200 experiment.

CUORE is a tonne-scale cryogenic detector operating at the Laboratori Nazionali del Gran Sasso (LNGS) that uses tellurium dioxide bolometers to search for neutrinoless double-beta decay of 130 Te. CUORE is also suitable to search for low energy rare events such as solar axions or WIMP scattering, thanks to its ultra-low background and large target mass. However, to conduct such sensitive searches requires improving the energy threshold to 10 keV. In this paper, we describe the analysis techniques developed for the low energy analysis of CUORE-like detectors, using the data acquired from November 2013 to March 2015 by CUORE-0, a single-tower prototype designed to validate the assembly procedure and new cleaning techniques of CUORE. We explain the energy threshold optimization, continuous monitoring of the trigger efficiency, data and event selection, and energy calibration at low energies in detail. We also present the low energy background spectrum of CUORE-0 below 60 keV . Finally, we report the sensitivity of CUORE to WIMP annual modulation using the CUORE-0 energy threshold and background, as well as an estimate of the uncertainty on the nuclear quenching factor from nuclear recoils inCUORE-0.

The cryogenic underground observatory for rare events (CUORE) is a 1-ton scale bolometric experiment whose detector consists of an array of 988 TeO 2 crystals arranged in a cylindrical compact structure of 19 towers. This will be the largest bolometric mass ever operated. The experiment will work at a temperature around or below 10 mK. CUORE cryostat consists of a cryogen-free system based on pulse tubes and a custom high power dilution refrigerator, designed to match these specifications. The cryostat has been commissioned in 2014 at the Gran Sasso National Laboratories and reached a record temperature of 6 mK on a cubic meter scale. In this paper, we present results of CUORE commissioning runs. Details on the thermal characteristics and cryogenic performances of the system will be also given.

We report on a search for double beta decay of \\[^{130}\\hbox {Te}\\] to the first \\[0^{+}\\] excited state of \\[^{130}\\hbox {Xe}\\] using a \\[9.8\\,\\hbox {kg}\\cdot \\hbox {yr}\\] exposure of \\[^{130}\\hbox {Te}\\] collected with the CUORE-0 experiment. In this work we exploit different topologies of coincident events to search for both the neutrinoless and two-neutrino double beta decay modes. We find no evidence for either mode and place lower bounds on the half-lives: \\[T^{0\\nu }_{0^+_1}>7.9\\cdot 10^{23}\\hbox {yr}\\] and \\[T^{2\\nu }_{0^+_1}>2.4\\cdot 10^{23}\\hbox {yr}\\] (\\[90\\%\\,\\hbox {CL}\\]). Combining our results with those obtained by the CUORICINO experiment, we achieve the most stringent constraints available for these processes: \\[T^{0\\nu }_{0^+_1}>1.4\\cdot 10^{24}\\hbox {yr}\\] and \\[T^{2\\nu }_{0^+_1}>2.5\\cdot 10^{23}\\hbox {yr}\\] (\\[90\\%\\,\\hbox {CL}\\]).

The MAJORANA DEMONSTRATOR is searching for double-beta decay of 76Ge to excited states (E.S.) in 76Se using a modular array of high purity Germanium detectors. 76Ge can decay into three E.S.s of 76Se. The E.S. decays have a clear event signature consisting of a ββ-decay with the prompt emission of one or two γ-rays, resulting in with high probability in a multi-site event. The granularity of the DEMONSTRATOR detector array enables powerful discrimination of this event signature from backgrounds. Using 21.3 kg-y of isotopic exposure, the DEMONSTRATOR has set world leading limits for each E.S. decay, with 90% CL lower half-life limits in the range of (0.56 ‒ 2.1) ⋅ 1024 y. In particular, for the 2v transition to the first 0+ E.S. of 76Se, a lower half-life limit of 0.68 ⋅ 1024 at 90% CL was achieved.

The MAJORANA DEMONSTRATOR is searching for double-beta decay of 76 Ge to excited states (E.S.) in 76 Se using a modular array of high purity Germanium detectors. 76 Ge can decay into three E.S.s of 76 Se. The E.S. decays have a clear event signature consisting of a ββ -decay with the prompt emission of one or two γ -rays, resulting in with high probability in a multi-site event. The granularity of the DEMONSTRATOR detector array enables powerful discrimination of this event signature from backgrounds. Using 21.3 kg-y of isotopic exposure, the DEMONSTRATOR has set world leading limits for each E.S. decay, with 90% CL lower half-life limits in the range of (0.56 ‒ 2.1) ⋅ 10 24 y. In particular, for the 2 v transition to the first 0 + E.S. of 76 Se, a lower half-life limit of 0.68 ⋅ 10 24 at 90% CL was achieved.

Abstract We report a study of the CUORE sensitivity to neutrinoless double beta ( $$0\\nu \\beta \\beta $$ 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 $$0\\nu \\beta \\beta $$ 0 ν β β decay half-life ( $$T_{1/2}^{\\,0\\nu }$$ T 1 / 2 0 ν ) at $$90\\%$$ 90 %  credibility interval (CI) – i.e. the interval containing the true value of $$T_{1/2}^{\\,0\\nu }$$ T 1 / 2 0 ν with $$90\\%$$ 90 % probability – and the $$3~\\sigma $$ 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 $$90\\%$$ 90 %  CI exclusion sensitivity of $$2\\cdot 10^{25}$$ 2 · 10 25  year with 3 months, and $$9\\cdot 10^{25}$$ 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 $$7\\cdot 10^{24}$$ 7 · 10 24  year and $$4\\cdot 10^{25}$$ 4 · 10 25  year, respectively.

Recent discussions about the origin of the Gallium Anomaly have motivated a remeasurement of the half life of \\(^{71}\\)Ge. We have conducted three separate measurements using dedicated planar Ge detectors: one with \\(^{55}\\)Fe as a standard, one with \\(^{57}\\)Co as a standard, and one stand alone 71Ge measurement. Our results yield a half life of 11.468 +- 0.008 days, which is consistent with but significantly more precise than the currently accepted value. With this experiment, the potential explanation of the Gallium Anomaly being due to an unexpectedly long \\(^{71}\\)Ge half life has been ruled out, leaving the origin of the anomaly as an open question.