Lavori di collaborazione

  • D. Q. Adams et al. (CUORE Collaboration). New Direct Limit on Neutrinoless Double Beta Decay Half-Life of 128Te with CUORE. Physical Review Letters 129, 222501 (2022). arxiv:2205.03132

    The Cryogenic Underground Observatory for Rare Events (CUORE) at Laboratori Nazionali del Gran Sasso of INFN in Italy is an experiment searching for neutrinoless double beta (0νββ) decay. Its main goal is to investigate this decay in 130Te, but its ton-scale mass and low background make CUORE sensitive to other rare processes as well. In this Letter, we present our first results on the search for 0νββ decay of 128Te, the Te isotope with the second highest natural isotopic abundance. We find no evidence for this decay, and using a Bayesian analysis we set a lower limit on the 128Te 0νββ decay half-life of T1/2>3.6×1024  yr (90% CI). This represents the most stringent limit on the half-life of this isotope, improving by over a factor of 30 the previous direct search results, and exceeding those from geochemical experiments for the first time.

  • D.Q. Adams et al. (CUORE Collaboration). An energy-dependent electro-thermal response model of CUORE cryogenic calorimeter. Journal of Instrumentation 17, P11023 (2022). arxiv:2205.04549

    The Cryogenic Underground Observatory for Rare Events (CUORE) is the most sensitive experiment searching for neutrinoless double-beta decay (0νββ) in 130Te. CUORE uses a cryogenic array of 988 TeO2 calorimeters operated at ∼10 mK with a total mass of 741 kg. To further increase the sensitivity, the detector response must be well understood. Here, we present a non-linear thermal model for the CUORE experiment on a detector-by-detector basis. We have examined both equilibrium and dynamic electro-thermal models of detectors by numerically fitting non-linear differential equations to the detector data of a subset of CUORE channels which are well characterized and representative of all channels. We demonstrate that the hot-electron effect and electric-field dependence of resistance in NTD-Ge thermistors alone are inadequate to describe our detectors' energy-dependent pulse shapes. We introduce an empirical second-order correction factor in the exponential temperature dependence of the thermistor, which produces excellent agreement with energy-dependent pulse shape data up to 6 MeV. We also present a noise analysis using the fitted thermal parameters and show that the intrinsic thermal noise is negligible compared to the observed noise for our detectors.

  • D.Q. Adams et al. (CUORE Collaboration). Search for neutrinoless double β+EC decay of 120Te with CUORE. Physical Review C 105, 6, 065504 (2022). arxiv:2203.08684

    The Cryogenic Underground Observatory for Rare Events (CUORE) is a large-scale cryogenic experiment searching for neutrinoless double-beta decay (0νββ) in 130Te. The CUORE detector is made of natural tellurium, providing the possibility of rare event searches on isotopes other than 130Te. In this work we describe a search for neutrinoless positron-emitting electron capture (β+EC) decay in 120Te with a total TeO2 exposure of 355.7 kg yr, corresponding to 0.2405 kg yr of 120Te. Albeit 0νββ with two final-state electrons represents the most promising channel, the emission of a positron and two 511-keV γ ’s make 0νβ+EC decay signature extremely clear. To fully exploit the potential offered by the detector modularity we include events with different topology and perform a simultaneous fit of five selected signal signatures. Using blinded data we extract a median exclusion sensitivity of 3.4 x 1022 yr at 90% credibility interval (C.I.). After unblinding we find no evidence of 0νβ+EC signal and set a 90% C.I. Bayesian lower limit of 2.9 x 1022 yr on the 120Te half-life. This result improves by an order of magnitude the existing limit from the combined analysis of CUORE-0 and Cuoricino.

  • C. Alduino et al. (CUORE Collaboration). Search for Majorana neutrinos exploiting millikelvin cryogenics with CUORE. Nature 604, 53-58 (2022). arxiv:2104.06906

    The possibility that neutrinos may be their own antiparticles, unique among the known fundamental particles, arises from the symmetric theory of fermions proposed by Ettore Majorana in 1937. Given the profound consequences of such Majorana neutrinos, among which is a potential explanation for the matter–antimatter asymmetry of the universe via leptogenesis, the Majorana nature of neutrinos commands intense experimental scrutiny globally; one of the primary experimental probes is neutrinoless double beta (0νββ) decay. Here we show results from the search for 0νββ decay of 130Te, using the latest advanced cryogenic calorimeters with the CUORE experiment. CUORE, operating just 10  millikelvin above absolute zero, has pushed the state of the art on three frontiers: the sheer mass held at such ultralow temperatures, operational longevity, and the low levels of ionizing radiation emanating from the cryogenic infrastructure. We find no evidence for 0νββ decay and set a lower bound of the process half-life as 2.2 × 1025  years at a 90 per cent credibility interval. We discuss potential applications of the advances made with CUORE to other fields such as direct dark matter, neutrino and nuclear physics searches and large-scale quantum computing, which can benefit from sustained operation of large payloads in a low-radioactivity, ultralow-temperature cryogenic environment.

    Link to supplementary material

  • D. Q. Adams et al. (CUORE Collaboration). CUORE opens the door to tonne-scale cryogenics experiments. Progress in Particle and Nuclear Physics 122, 103902 (2022).

    The past few decades have seen major developments in the design and operation of cryogenic particle detectors. This technology offers an extremely good energy resolution – comparable to semiconductor detectors – and a wide choice of target materials, making low temperature calorimetric detectors ideal for a variety of particle physics applications. Rare event searches have continued to require ever greater exposures, which has driven them to ever larger cryogenic detectors, with the CUORE experiment being the first to reach a tonne-scale, mK-cooled, experimental mass. CUORE, designed to search for neutrinoless double beta decay, has been operational since 2017 at a temperature of about 10 mK. This result has been attained by the use of an unprecedentedly large cryogenic infrastructure called the CUORE cryostat: conceived, designed and commissioned for this purpose. In this article the main characteristics and features of the cryogenic facility developed for the CUORE experiment are highlighted. A brief introduction of the evolution of the field and of the past cryogenic facilities are given. The motivation behind the design and development of the CUORE cryogenic facility is detailed as are the steps taken toward realization, commissioning, and operation of the CUORE cryostat. The major challenges overcome by the collaboration and the solutions implemented throughout the building of the cryogenic facility will be discussed along with the potential improvements for future facilities. The success of CUORE has opened the door to a new generation of large-scale cryogenic facilities in numerous fields of science. Broader implications of the incredible feat achieved by the CUORE collaboration on the future cryogenic facilities in various fields ranging from neutrino and dark matter experiments to quantum computing will be examined.

  • C. Alduino et al. (CUORE Collaboration). Search for double-beta decay of 130Te to the 0+ states of 130Xe with CUORE. Eur. Phys. J. C 81, 567 (2021). arxiv:2101.10702

    The CUORE experiment is a large bolometric array searching for the lepton number violating neutrino-less double beta decay (0νββ) in the isotope 130Te. In this work we present the latest results on two searches for the double beta decay (DBD) of 130Te to the first 0+2 excited state of 130Xe: the 0νββ decay and the Standard Model-allowed two-neutrinos double beta decay (2νββ). Both searches are based on a 372.5 kg×yr TeO2 exposure. The de-excitation gamma rays emitted by the excited Xe nucleus in the final state yield a unique signature, which can be searched for with low background by studying coincident events in two or more bolometers. The closely packed arrangement of the CUORE crystals constitutes a significant advantage in this regard. The median limit setting sensitivities at 90% Credible Interval (C.I.) of the given searches were estimated as S1/2 = 5.6×1024 yr for the 0νββ decay and S1/2 = 2.1×1024 yr for the 2νββ decay. No significant evidence for either of the decay modes was observed and a Bayesian lower bound at 90% C.I. on the decay half lives is obtained as: (T1/2)0+2 > 5.9×1024 yr for the 0νββ mode and (T1/2)0+2 > 1.9×1024 yr for the 2νββ mode. These represent the most stringent limits on the DBD of 130Te to excited states and improve by a factor ~5 the previous results on this process.

  • D. Q. Adams et al. (CUORE Collaboration). Measurement of the 2νββ Decay Half-Life of 130Te with CUORE. Phys. Rev. Lett. 126, 171801 (2021). arxiv:2012.11749v1

    We measured two-neutrino double beta decay of 130Te using an exposure of 300.7 kg⋅yr accumulated with the CUORE detector. Using a Bayesian analysis to fit simulated spectra to experimental data, it was possible to disentangle all the major background sources and precisely measure the two-neutrino contribution. The half-life is in agreement with past measurements with a strongly reduced uncertainty: T1/2 =7.71+0.08−0.06(stat)++0.12−0.15(syst)×1020 yr. This measurement is the most precise determination of the 130 Te 2νββ decay half-life to date.

  • I. Nutini et al. (CUORE Collaboration). The CUORE Detector and Results. J. Low Temp. Phys. 199, 519–528 (2020).

    The cryogenic underground observatory for rare events (CUORE) is a cryogenic experiment searching for neutrinoless double beta decay (0νββ) of 130Te. The detector consists of an array of 988 TeO2 crystals arranged in a compact cylindrical structure of 19 towers. We report the CUORE initial operations and optimization campaigns. We then present the CUORE results on 0νββ and 2νββ decay of 130Te obtained from the analysis of the physics data acquired in 2017.

  • D. Q. Adamset al. (CUORE Collaboration). Improved Limit on Neutrinoless Double-Beta Decay in Te-130 with CUORE. Phys. Rev. Lett. 124, 122501 (2020).

    We report new results from the search for neutrinoless double-beta decay in 130Te with the CUORE detector. This search benefits from a fourfold increase in exposure, lower trigger thresholds, and analysis improvements relative to our previous results. We observe a background of (1.38 ± 0.07) 10-2 counts/(keV⋅kg⋅yr) in the 0νββ decay region of interest and, with a total exposure of 372.5 kg⋅yr, we attain a median exclusion sensitivity of 1.7 × 1025 yr. We find no evidence for 0νββ decay and set a 90% credibility interval Bayesian lower limit of 3.2 × 1025 yr on the 130Te half-life for this process. In the hypothesis that 0νββ decay is mediated by light Majorana neutrinos, this results in an upper limit on the effective Majorana mass of 75–350 meV, depending on the nuclear matrix elements used.

  • C. Alduino et al. (CUORE Collaboration). Double-beta decay of Te-130 to the first 0+ excited state of Xe-130 with CUORE-0. The European Physical Journal C 79, 795 (2019). arxiv:1811.10363

    We report on a search for double beta decay of 130Te to the first 0+ excited state of 130Xe using a 9.8 kg yr exposure of 130Te 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: T0+1 > 7.9×1023 yr and T0+1 > 2.4×1023 (90% CL). Combining our results with those obtained by the CUORICINO experiment, we achieve the most stringent constraints available for these processes: T0+1 > 1.4×1024 yr and T0+1 > 2.5×1023 yr (90% CL).

  • A.Caminata et al. (CUORE Collaboration). Results from the Cuore Experiment. Universe 5(1), 10 (2019).

    The Cryogenic Underground Observatory for Rare Events (CUORE) is the first bolometric experiment searching for neutrinoless double beta decay that has been able to reach the 1-ton scale. The detector consists of an array of 988 TeO2 crystals arranged in a cylindrical compact structure of 19 towers, each of them made of 52 crystals. The construction of the experiment was completed in August 2016 and the data taking started in spring 2017 after a period of commissioning and tests. In this work we present the neutrinoless double beta decay results of CUORE from examining a total TeO2 exposure of 86.3 kg yr, characterized by an effective energy resolution of 7.7 keV FWHM and a background in the region of interest of 0.014 counts/(keV kg yr). In this physics run, CUORE placed a lower limit on the decay half-life of neutrinoless double beta decay of 130Te > 1.3×1025 yr (90% C.L.). Moreover, an analysis of the background of the experiment is presented as well as the measurement of the 130Te 2νββ decay with a resulting half-life of T1/2=[7.9±0.1(stat.)±0.2(syst.)]×1020 yr which is the most precise measurement of the half-life and compatible with previous results.

  • C. Alduino et al. (CUORE Collaboration). Search for Neutrinoless β+EC Decay of Te-120 with CUORE-0. Phys. Rev. C 97, 055502 (2018). arxiv:1710.07459

    We have performed a search for neutrinoless β+EC decay of 120Te using the final CUORE-0 data release. We describe a new analysis method for the simultaneous fit of signatures with different event topology, and of data subsets with different signal efficiency, obtaining a limit on the half-life of the decay of T1/2 > 1.6 × 1021 yr at 90% CI. Combining this with results from Cuoricino, a predecessor experiment, we obtain the strongest limit to date, corresponding to T1/2 > 2.7 × 1021 yr at 90% CI.

  • C. Alduino et al. (CUORE Collaboration). Study of rare nuclear processes with CUORE. International Journal of Modern Physics A 33, No. 09 (2018). arxiv:1801.05403

    TeO2 bolometers have been used for many years to search for neutrinoless double beta decay in 130-Te. CUORE, a tonne-scale TeO2 detector array, recently published the most sensitive limit on the half-life, T0ν1/2>1.5×1025yr, which corresponds to an upper bound of 140−400~meV on the effective Majorana mass of the neutrino. While it makes CUORE a world-leading experiment looking for neutrinoless double beta decay, it is not the only study that CUORE will contribute to in the field of nuclear and particle physics. As already done over the years with many small-scale experiments, CUORE will investigate both rare decays (such as the two-neutrino double beta decay of 130-Te and the hypothesized electron capture in 123-Te), and rare processes (e.g., dark matter and axion interactions). This paper describes some of the achievements of past experiments that used TeO2 bolometers, and perspectives for CUORE.

  • C. Alduino et al. (CUORE Collaboration). First Results from CUORE: A Search for Lepton Number Violation via 0νββ Decay of Te-130. Phys. Rev. Lett. 120, 132501 (2018). arxiv:1710.07988

    The CUORE experiment, a ton-scale cryogenic bolometer array, recently began operation at the Laboratori Nazionali del Gran Sasso in Italy. The array represents a significant advancement in this technology, and in this work we apply it for the first time to a high-sensitivity search for a lepton-number–violating process: 130Te neutrinoless double-beta decay. Examining a total TeO2 exposure of 86.3 kg⋅yr, characterized by an effective energy resolution of (7.7 ± 0.5) keV FWHM and a background in the region of interest of (0.014 ± 0.002) counts/(keV⋅kg⋅yr), we find no evidence for neutrinoless double-beta decay. The median statistical sensitivity of this search is 7.0 × 1024 yr. Including systematic uncertainties, we place a lower limit on the decay half-life of T1∕2 > 1.3 × 1025 yr (90% C.L.). Combining this result with those of two earlier experiments, Cuoricino and CUORE-0, we find T1∕2 > 1.5 × 1025 yr (90% C.L.), which is the most stringent limit to date on this decay. Interpreting this result as a limit on the effective Majorana neutrino mass, we find mββ < 140–400 meV, where the range reflects the nuclear matrix element estimates employed.

  • C. Alduino et al. (CUORE Collaboration). Low Energy Analysis Techniques for CUORE. European Physical Journal C 77, 857 (2017). arxiv:1708.07809

    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 130Te. 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 60keV. 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 in CUORE-0.

  • C. Alduino et al. (CUORE Collaboration). The projected background for the CUORE experiment. European Physical Journal C 77, 543 (2017). arxiv:1704.08970

    The Cryogenic Underground Observatory for Rare Events (CUORE) is designed to search for neutrinoless double beta decay of 130Te with an array of 988 TeO2 bolometers operating at temperatures around 10 mK. The experiment is currently being commissioned in Hall A of Laboratori Nazionali del Gran Sasso, Italy. The goal of CUORE is to reach a 90% C.L. exclusion sensitivity on the 130Te decay half-life of 9 × 1025 years after 5 years of data taking. The main issue to be addressed to accomplish this aim is the rate of background events in the region of interest, which must not be higher than 10−2 counts/keV/kg/y. We developed a detailed Monte Carlo simulation, based on results from a campaign of material screening, radioassays, and bolometric measurements, to evaluate the expected background. This was used over the years to guide the construction strategies of the experiment and we use it here to project a background model for CUORE. In this paper we report the results of our study and our expectations for the background rate in the energy region where the peak signature of neutrinoless double beta decay of 130Te is expected.

  • C. Alduino et al. (CUORE Collaboration). CUORE Sensitivity to 0νββ Decay. European Physical Journal C 77, 532 (2017). arxiv:1705.10816

    We report a study of the CUORE sensitivity to neutrinoless double beta (0νββ) decay. We used a Bayesian analysis based on a toy Monte Carlo (MC) approach to extract the exclusion sensitivity to the 0νββ decay half-life (T1/2) at 90% credibility interval (CI) — i.e. the interval containing the true value of T1/2 with 90% probability — and the 3σ 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 × 1025 yr with 3 months, and 9 × 1025 yr with 5 years of live time. Under the same conditions, the discovery sensitivity after 3 months and 5 years will be 7 × 1024  and 4 × 1025 yr, respectively.

  • C. Alduino et al. (CUORE Collaboration). Measurement of the Two-Neutrino Double Beta Decay Half-life of Te-130 with the CUORE-0 Experiment. European Physical Journal C 77, 13 (2017). arxiv:1609.01666

    We report on the measurement of the two-neutrino double beta decay half-life of 130Te with the CUORE-0 detector. From an exposure of 33.4 kg⋅y of TeO2, the half-life is determined to be T1/2 = [8.2 ± 0.2 (stat.) ± 0.6 (syst.)] × 1020 y. 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 130Te neutrinoless double beta decay region of interest.

  • C. Alduino et al. (CUORE Collaboration). CUORE-0 detector: design, construction and operation. Journal of Instrumentation 11, P07009 (2016). arxiv:1604.05465

    The CUORE experiment will search for neutrinoless double-beta decay of 130Te with an array of 988 TeO2 bolometers arranged in 19 towers. CUORE-0, the first tower assembled according to the CUORE procedures, was built and commissioned at Laboratori Nazionali del Gran Sasso, and took data from March 2013 to March 2015. In this paper we describe the design, construction and operation of the CUORE-0 experiment, with an emphasis on the improvements made over a predecessor experiment, Cuoricino. In particular, we demonstrate with CUORE-0 data that the design goals of CUORE are within reach.

  • C. Alduino et al. (CUORE Collaboration). Analysis Techniques for the Evaluation of the Neutrinoless Double-β Decay Lifetime in Te-130 with CUORE-0. Physical Review C 93, 045503 (2016). arxiv:1601.01334

    We describe in detail the methods used to obtain the lower bound on the lifetime of neutrinoless double-beta (0νββ) decay in 130Te and the associated limit on the effective Majorana mass of the neutrino using the CUORE-0 detector. CUORE-0 is a bolometric detector array located at the Laboratori Nazionali del Gran Sasso that was designed to validate the background reduction techniques developed for CUORE, a next-generation experiment scheduled to come online in 2016. CUORE-0 is also a competitive 0νββ decay search in its own right and functions as a platform to further develop the analysis tools and procedures to be used in CUORE. These include data collection, event selection and processing, as well as an evaluation of signal efficiency. In particular, we describe the amplitude evaluation, thermal gain stabilization, energy calibration methods, and the analysis event selection used to create our final 0νββ decay search spectrum. We define our high level analysis procedures, with emphasis on the new insights gained and challenges encountered. We outline in detail our fitting methods near the hypothesized 0νββ decay peak and catalog the main sources of systematic uncertainty. Finally, we derive the 0νββ decay half-life limits previously reported for CUORE-0, T1∕2 > 2.7 × 1024 yr, and in combination with the Cuoricino limit, T1∕2 > 4.0 × 1024 yr.

  • K. Alfonso et al. (CUORE Collaboration). Search for Neutrinoless Double-Beta Decay of Te-130 with CUORE-0. Physical Review Letters 115, 102502 (2015). arxiv:1504.02454

    We report the results of a search for neutrinoless double-beta decay in a 9.8 kg⋅yr exposure of 130Te using a bolometric detector array, CUORE-0. The characteristic detector energy resolution and background level in the region of interest are 5.1 ± 0.3 keV FWHM and 0.058 ± 0.004 (stat.) ± 0.002 (syst.) counts/(keV⋅kg⋅yr), respectively. The median 90% C.L. lower-limit sensitivity of the experiment is 2.9 × 1024 yr and surpasses the sensitivity of previous searches. We find no evidence for neutrinoless double-beta decay of 130Te and place a Bayesian lower bound on the decay half-life, T1∕2 > 2.7 × 1024 yr at 90% C.L. Combining CUORE-0 data with the the 19.75 kg⋅yr exposure of 130Te from the Cuoricino experiment we obtain T1∕2 > 4.0 × 1024 yr at 90% C.L. (Bayesian), the most stringent limit to date on this half-life. Using a range of nuclear matrix element estimates we interpret this as a limit on the effective Majorana neutrino mass, mββ < 270–760 meV.

  • D. R. Artusa et al. (CUORE Collaboration). Exploring the neutrinoless double beta decay in the inverted neutrino hierarchy with bolometric detectors. European Physical Journal C 74, 3096 (2014). arxiv:1404.4469

    Neutrinoless double beta decay (0νββ) 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 0νββ 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 0νββ 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 (|mee|) 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.

  • D. R. Artusa et al. (CUORE Collaboration). Initial performance of the CUORE-0 experiment. European Physical Journal C 74, 2956 (2014). arxiv:1402.0922

    CUORE-0 is a cryogenic detector that uses an array of tellurium dioxide bolometers to search for neutrinoless double-beta decay of 130Te. We present the first data analysis with 7.1 kg⋅yr of total TeO2 exposure focusing on background measurements and energy resolution. The background rates in the neutrinoless double-beta decay region of interest (2.47 to 2.57 MeV) and in the α background-dominated region (2.70 to 3.90 MeV) have been measured to be 0.07 ± 0.011 and 0.019 ± 0.002 counts/(keV⋅kg⋅y), respectively. The latter result represents a factor of 6 improvement from a predecessor experiment, Cuoricino. The results verify our understanding of the background sources in CUORE-0, which is the basis of extrapolations to the full CUORE detector. The obtained energy resolution (full width at half maximum) in the region of interest is 5.7 keV. Based on the measured background rate and energy resolution in the region of interest, CUORE-0 half-life sensitivity is expected to surpass the observed lower bound of Cuoricino with one year of live time.

  • D. R. Artusa et al. (CUORE Collaboration). Searching for Neutrinoless Double-Beta Decay of Te-130 with CUORE. Advances in High Energy Physics 2015, 1 (2015). arxiv:1402.6072

    Neutrinoless double-beta (0νββ) 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 0νββ 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 0νββ decay half-life sensitivity after five years of livetime is 1.6  × 1026  y at 1σ (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.

  • CUORE Collaboration. Search for 14.4 keV solar axions from M1 transition of Fe-57 with CUORE crystals. Journal of Cosmology and Astroparticle Physics 2013, 7 (2013). arxiv:1209.2800

    We report the results of a search for axions from the 14.4 keV M1 transition from 57Fe in the core of the sun using the axio-electric effect in TeO2 bolometers. The detectors are 5 × 5 × 5 cm3 crystals operated at about 10 mK in a facility used to test bolometers for the CUORE experiment at the Laboratori Nazionali del Gran Sasso in Italy. An analysis of 43.65 kg⋅d of data was made using a newly developed low energy trigger which was optimized to reduce the energy threshold of the detector. An upper limit of 0.58 c⋅kg−1⋅d−1 is established at 95% C.L., which translates into lower bounds fA ≥ 3.12 × 105 GeV 95% C.L. (DFSZ model) and fA ≥ 2.41 × 104 95% C.L. (KSVZ model) on the Peccei-Quinn symmetry-breaking scale, for a value of S = 0.5 of the flavor-singlet axial vector matrix element. These bounds can be expressed in terms of axion masses as mA ≤ 19.2 eV and mA ≤ 250 eV at 95% C.L. in the DFSZ and KSVZ models respectively. Bounds are given also for the interval 0.35 ≤ S ≤ 0.55.

  • F. Alessandria et al. (CUORE Collaboration). Validation of techniques to mitigate copper surface contamination in CUORE. Astroparticle Physics 45, 13-22 (2013). arxiv:arXiv:1210.1107

    In this article we describe the background challenges for the CUORE experiment posed by surface contamination of inert detector materials such as copper, and present three techniques explored to mitigate these backgrounds. Using data from a dedicated test apparatus constructed to validate and compare these techniques we demonstrate that copper surface contamination levels better than 10−7-10−8 Bq/cm2 are achieved for 238U and 232Th. If these levels are reproduced in the final CUORE apparatus the projected 90% C.L. upper limit on the number of background counts in the region of interest is 0.02–0.03 counts/keV/kg/y depending on the adopted mitigation technique.

  • F. Alessandria et al. (CUORE Collaboration). The low energy spectrum of TeO2 bolometers: results and dark matter perspectives for the CUORE-0 and CUORE experiments. Journal of Cosmology and Astroparticle Physics 2013, 038 (2013). arxiv:1209.2519

    We collected 19.4 days of data from four 750 g TeO2 bolometers, and in three of them we were able to set the energy threshold around 3 keV using a new analysis technique. We found a background rate ranging from 25 cpd/keV/kg at 3 keV to 2 cpd/keV/kg at 25 keV, and a peak at 4.7 keV. The origin of this peak is presently unknown, but its presence is confirmed by a reanalysis of 62.7 kg days of data from the finished CUORICINO experiment. Finally, we report the expected sensitivities of the CUORE-0 (52 bolometers) and CUORE (988 bolometers) experiments to a WIMP annual modulation signal.

  • The CUORICINO experiment was an array of 62 TeO2 single-crystal bolometers with a total 130Te mass of 11.3 kg. The experiment finished in 2008 after more than 3 yr of active operating time. Searches for both 0ν and 2ν double-β decay to the first excited 0+ state in 130Xe were performed by studying different coincidence scenarios. The analysis was based on data representing a total exposure of N(130Te)⋅t = 9.5×1025 yr. No evidence for a signal was found. The resulting lower limits on the half-lives are T1/2(130Te→130Xe*) > 1.3×1023 yr (90% C.L.), and T1/2(130Te→130Xe*) > 9.4×1023 yr (90% CL).

  • F. Alessandria et al. (CUORE Collaboration). CUORE crystal validation runs: Results on radioactive contamination and extrapolation to CUORE background. Astroparticle Physics 35, 839-849 (2012). arxiv:1108.4757

    The CUORE Crystal Validation Runs (CCVRs) have been carried out since the end of 2008 at the Gran Sasso National Laboratories, in order to test the performance and the radiopurity of the TeO2 crystals produced at SICCAS (Shanghai Institute of Ceramics, Chinese Academy of Sciences) for the CUORE experiment. In this work the results of the first 5 validation runs are presented. Results have been obtained for bulk contaminations and surface contaminations from several nuclides. An extrapolation to the CUORE background has been performed.

  • E. Andreotti et al. (Cuoricino Collaboration). Te-130 neutrinoless double-beta decay with CUORICINO. Astroparticle Physics 34, 822-831 (2011). arxiv:1012.3266

    We report the final result of the CUORICINO experiment. Operated between 2003 and 2008, with a total exposure of 19.75 kg y of 130Te, CUORICINO was able to set a lower bound on the 130Te 0νββ half-life of 2.8 × 1024 years at 90% C.L. The limit here reported includes the effects of systematic uncertainties that are examined in detail in the paper. The corresponding upper bound on the neutrino Majorana mass is in the range 300–710 meV, depending on the adopted nuclear matrix element evaluation.

  • E. Andreotti et al. (Cuoricino Collaboration). Search for β+/EC double beta decay of Te-120. Astroparticle Physics 34, 643-648 (2011). arxiv:1011.4811

    We present a search for β+/EC double beta decay of 120Te performed with the CUORICINO experiment, an array of TeO2 cryogenic bolometers. After collecting 0.0573 kg·y of 120Te, we see no evidence of a signal and therefore set the following limits on the half-life: T1/2 > 1.9 × 1021 yr at 90% C.L. for the 0ν mode and T1/2 > 7.6 × 1019 yr at 90% C.L. for the 2ν mode. These results improve the existing limits by almost three orders of magnitude (four in the case of 0ν mode).

  • C. Arnaboldi et al. (CUORE Collaboration). Production of high purity TeO2 single crystals for the study of neutrinoless double beta decay. Journal of Crystal Growth 312, 2999-3008 (2010). arxiv:1005.3686

    High purity TeO2 crystals are produced to be used for the search for the neutrinoless double beta decay of 130Te. Dedicated production lines for raw material synthesis, crystal growth, and surface processing were built compliant with radio-purity constraints specific to rare event physics experiments. High sensitivity measurements of radio-isotope concentrations in raw materials, reactants, consumables, ancillaries, and intermediary products used for TeO2 crystals production are reported. Indications are given on the crystals perfection and how it is achieved and maintained in a large scale production process. Production and certification protocols are presented and resulting ready-to-use TeO2 crystals are described.

  • E. Andreotti et al. (Cuoricino Collaboration). Muon-induced backgrounds in the CUORICINO experiment. Astroparticle Physics 34, 18-24 (2010). arxiv:0912.3779

    To better understand the contribution of cosmic ray muons to the CUORICINO background, 10 plastic scintillator detectors were installed at the CUORICINO site and operated during the final 3 months of the experiment. From these measurements, an upper limit of 0.0021 counts/(keV kg yr) (95% CL) was obtained on the cosmic ray-induced background in the neutrinoless double beta decay region of interest. The measurements were also compared to Geant4 simulations.

  • C. Arnaboldi et al. (Cuoricino Collaboration). Results from a search for the 0νββ-decay of Te-130. Physical Review C 78, 035502 (2008). arxiv:0802.3439

    A detailed description of the CUORICINO 130Te neutrinoless double-beta (0νββ) decay experiment is given and recent results are reported. CUORICINO is an array of 62 tellurium oxide (TeO2) bolometers with an active mass of 40.7 kg. It is cooled to ~8−10 mK by a dilution refrigerator shielded from environmental radioactivity and energetic neutrons. It is running in the Laboratori Nazionali del Gran Sasso (LNGS) in Assergi, Italy. These data represent an exposure of 11.83 kg yr or 91 mole-years of 130Te. No evidence for 0νββ-decay was observed and a limit of T0ν1/2(130Te) ≥ 3.0 × 1024 y (90% CL) is set. This corresponds to an upper limit on the effective mass, <mν>, between 0.19 and 0.68 eV when analyzed with the many published nuclear structure calculations. In the context of these nuclear models, the values fall within the range corresponding to the claim of evidence of 0νββ-decay by H. V. Klapdor-Kleingrothaus et al. The experiment continues to acquire data.

  • C. Arnaboldi et al. (Cuoricino Collaboration). New Limit on the Neutrinoless ββ Decay of Te-130. Physical Review Letters 95, 142501 (2005). arxiv:hep-ex/0501034

    We report the present results of CUORICINO, a search for neutrinoless double-beta (0νββ) decay of 130Te. The detector is an array of 62 TeO2 bolometers with a total active mass of 40.7 kg. The array is cooled by a dilution refrigerator shielded from environmental radioactivity and energetic neutrons, operated at ~8  mK in the Gran Sasso Underground Laboratory. No evidence for 0νββ decay was found and a new lower limit, T1/2&geq;1.8 × 1024   yr (90% C.L.) is set, corresponding to ≤mν ≥ 0.2 to 1.1 eV, depending on the theoretical nuclear matrix elements used in the analysis.

  • R. Ardito et al. (CUORE Collaboration). CUORE: A Cryogenic Underground Observatory for Rare Events. arxiv:hep-ex/0501010

    Recently, neutrino oscillation experiments have unequivocally demonstrated that neutrinos have mass and mix. These experiments have yielded valuable information on the mixing angles and on the mass differences of the three eigenstates but cannot determine the scale of the neutrino mass, which is fixed by the lightest neutrino mass eigenvalue. This can only be directly determined by kinematic measurements or by the observation and measurement of the neutrinoless double-beta decay (NDBD) half-life. The CUORE experiment is designed with a sensitivity capable of probing the range indicated by oscillation experiments. It consists of an array of 988, 750 g, TeO2 bolometers operating at 8 to 10 mK and arranged in a cylindrical geometry of 19 towers hanging on the bottom of the mixing chamber of a dilution refrigerator. Each tower consists of 13 4-detector modules for a total of 52 bolometers. One such tower has been successfully constructed and is now operated in the Gran Sasso Laboratory as a test experiment, and also as an independent NDBD experiment called CUORICINO. In fact, the 3 year half-life sensitivity of CUORICINO for NDBD decay of 130Te is 6.1 × 1024 years. Thus far the CUORICINO data demonstrate the technical feasibility of the expanded CUORE array while showing what and where the sources of background are and how to reduce them. A background reduction to 0.01 counts/keV/kg/y in the NDBD energy region is therefore possible. This would allow the full CUORE array to achieve a 5-year sensitivity of the order of 30 meV on the effective neutrino mass. Another order of magnitude reduction (corresponding to a sensitivity of about 15 meV) will present a real challenge, but is also possible. The CUORE experiment will be installed in the Laboratori Nazionali del Gran Sasso (LNGS) in Assergi, Italy.

  • C. Arnaboldi et al. (CUORE Collaboration). CUORE: A cryogenic underground observatory for rare events. Nuclear Instruments and Methods A 518, 775-798 (2004). arxiv:hep-ex/0212053

    CUORE is a proposed tightly packed array of 1000 TeO2 bolometers, each being a cube 5 cm on a side with a mass of 760 g: The array consists of 25 vertical towers, arranged in a square of 5 towers × 5 towers, each containing 10 layers of four crystals. The design of the detector is optimized for ultralow-background searches: for neutrinoless double-beta decay of 130 Te (33.8% abundance), cold dark matter, solar axions, and rare nuclear decays. A preliminary experiment involving 20 crystals 3 × 3 × 6 cm3 of 340 g has been completed, and a single CUORE tower is being constructed as a smaller-scale experiment called CUORICINO. The expected performance and sensitivity, based on Monte Carlo simulations and extrapolations of present results, are reported.

  • C. Arnaboldi et al. (Cuoricino Collaboration). First results on neutrinoless double beta decay of Te-130 with the calorimetric CUORICINO experiment. Physics Letters B 584, 260-268 (2004).

    The first results are reported on the limit for neutrinoless double decay of 130Te obtained with the new bolometric experiment CUORICINO. The set-up consists of 44 cubic crystals of natural TeO2, 5 cm on the side and 18 crystals of 3 × 3 × 6 cm3. Four of these latter crystals are made with isotopically enriched materials: two in 128Te and two others in 130Te. With a sensitive mass of ~40 kg, our array is by far the most massive running cryogenic detector to search for rare events. The array is operated at a temperature of ~10 mK in a dilution refrigerator under a heavy shield in the Gran Sasso Underground Laboratory at a depth of about 3500 m.w.e. The counting rate in the region of neutrinoless double beta decay is ~0.2 counts keV−1 kg−1 y−1 , among the lowest in this type of experiment. No evidence for neutrinoless double beta decay is found with the present statistics obtained in about three months with a live time of 72%. The corresponding lower limit for the lifetime of this process is of 5.5 × 1023 years at 90% C.L. The corresponding limit for the effective neutrino mass ranges between 0.37 to 1.9 eV depending on the theoretically calculated nuclear matrix elements used. This constraint is the most restrictive one except those obtained with Ge diodes, and is comparable to them.

  • C. Arnaboldi et al. (CUORE Collaboration). Physics potential and prospects for the CUORICINO and CUORE experiments. Astroparticle Physics 20, 91-110 (2003). arxiv:hep-ex/0302021

    The Cryogenic Underground Observatory for Rare Events (CUORE) experiment projects to construct and operate an array of 1000 cryogenic thermal detectors of TeO2, of a mass of 760 g each, to investigate rare events physics, in particular, double beta decay and non-baryonic particle dark matter. A first step towards CUORE is CUORICINO, an array of 62 bolometers, currently being installed in the Gran Sasso Laboratory. In this paper we report the physics potential of both stages of the experiment regarding neutrinoless double beta decay of 130Te, WIMP searches and solar axions.