Collaboration papers

  • 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  × 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.