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 S^0ν_1/2 = 5.6×10²⁴ yr for the 0νββ decay and S^2ν_1/2 = 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: (T_1/2)^0ν_0⁺2 > 5.9×10²⁴ yr for the 0νββ mode and (T_1/2)^2ν_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.

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: T^2ν_1/2 =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.

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.

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.

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: T^0ν_0⁺1 > 7.9×10²³ yr and T^2ν_0⁺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: T^0ν_0⁺1 > 1.4×10²⁴ yr and T^2ν_0⁺1 > 2.5×10²³ yr (90% CL).

TeO₂ bolometers have been used for many years to search for neutrinoless double beta decay in ¹³⁰Te. CUORE, a tonne-scale TeO₂ detector array, recently published the most sensitive limit on the half-life, T^0ν_1/2>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 ¹³⁰Te and the hypothesized electron capture in ¹²³Te), 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.

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 T_1/2 > 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 T_1/2 > 2.7 × 10²¹ yr at 90% CI.

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 T_1∕2^0ν > 1.3 × 10²⁵ yr (90% C.L.). Combining this result with those of two earlier experiments, Cuoricino and CUORE-0, we find T_1∕2^0ν > 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 m_ββ < 140–400 meV, where the range reflects the nuclear matrix element estimates employed.

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.