arXiv subjects

R. G. Huang

Publications and source records attributed to R. G. Huang.

16 recordsLinked to original sources

arXiv2025

New direct limit on neutrinoless double beta decay half-life of $^{128}$Te with CUORE

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 (0$νββ$) decay. Its main goal is to investigate this decay in $^{130}$Te, but its ton-scale mass and low background make CUORE sensitive to other rare processes as well. In this work, we present our first results on the search for \nbb decay of $^{128}$Te, 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 $^{128}$Te \nbb decay half-life of T$_{1/2} > 3.6 \times 10^{24}$ yr (90\% CI). This represents the most stringent limit on the half-life of this isotope, improving by over a factor 30 the previous direct search results, and exceeding those from geochemical experiments for the first time.

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arXiv2022

An Energy-dependent Electro-thermal Response Model of CUORE Cryogenic Calorimeter

The Cryogenic Underground Observatory for Rare Events (CUORE) is the most sensitive experiment searching for neutrinoless double-beta decay ($0νββ$) in $^{130}\text{Te}$. CUORE uses a cryogenic array of 988 TeO$_2$ calorimeters operated at $\sim$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.

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arXiv2022

Search for Neutrinoless $β^+EC$ Decay of $^{120}$Te with CUORE

CUORE is a large scale cryogenic experiment searching for neutrinoless double beta decay ($0νββ$) in $^{130}$Te. The CUORE detector is made of natural tellurium, providing the possibility of rare event searches on isotopes other than $^{130}$Te. In this work we describe a search for neutrinoless positron emitting electron capture ($0νβ^+EC$) decay in $^{120}$Te with a total TeO$_2$ exposure of 355.7 kg $\cdot$ yr, corresponding to 0.2405 kg $\cdot$ yr of $^{120}$Te. Albeit $0 νββ$ 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 $3.4 \cdot 10^{22}$ 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 $2.9 \cdot 10^{22}$ yr on $^{120}$Te half-life. This result improves by an order of magnitude the existing limit from the combined analysis of CUORE-0 and Cuoricino.

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arXiv2022

Search for Majorana neutrinos exploiting millikelvin cryogenics with CUORE

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 ($0 νββ$) decay. Here we show results from the search for $0 νββ$ decay of $^{130}$Te, 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 ultra-low temperatures, operational longevity, and the low levels of ionising radiation emanating from the cryogenic infrastructure. We find no evidence for $0 νββ$ decay and set a lower bound of $T_{1/2}^{0 ν} > 2.2 \times 10^{25}$ years at a 90% 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, ultra-low temperature cryogenic environment.

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arXiv2022

Toward CUPID-1T

Current experiments to search for broken lepton-number symmetry through the observation of neutrinoless double-beta decay ($0\mathrm{νββ}$) provide the most stringent limits on the Majorana nature of neutrinos and the effective Majorana neutrino mass ($m_{ββ}$). The next-generation experiments will focus on the sensitivity to the $0\mathrm{νββ}$ half-life of $\mathcal{O}(10^{27}$--$10^{28}$~years$)$ and $m_{ββ}\lesssim15$~meV, which would provide complete coverage of the so-called Inverted Ordering region of the neutrino mass parameter space. By taking advantage of recent technological breakthroughs, new, future calorimetric experiments at the 1-ton scale can increase the sensitivity by at least another order of magnitude, exploring the large fraction of the parameter space that corresponds to the Normal neutrino mass ordering. In case of a discovery, such experiments could provide important insights toward a new understanding of the mechanism of $0\mathrm{νββ}$. We present here a series of projects underway that will provide advancements in background reduction, cryogenic readout, and physics searches beyond $0\mathrm{νββ}$, all moving toward the next-to-next generation CUPID-1T detector.

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arXiv2022

Optimization of the first CUPID detector module

CUPID will be a next generation experiment searching for the neutrinoless double $β$ decay, whose discovery would establish the Majorana nature of the neutrino. Based on the experience achieved with the CUORE experiment, presently taking data at LNGS, CUPID aims to reach a background free environment by means of scintillating Li$_{2}$$^{100}$MoO$_4$ crystals coupled to light detectors. Indeed, the simultaneous heat and light detection allows us to reject the dominant background of $α$ particles, as proven by the CUPID-0 and CUPID-Mo demonstrators. In this work we present the results of the first test of the CUPID baseline module. In particular, we propose a new optimized detector structure and light sensors design to enhance the engineering and the light collection, respectively. We characterized the heat detectors, achieving an energy resolution of (5.9 $\pm$ 0.2) keV FWHM at the $Q$-value of $^{100}$Mo (about 3034 keV). We studied the light collection of the baseline CUPID design with respect to an alternative configuration which features gravity-assisted light detectors' mounting. In both cases we obtained an improvement in the light collection with respect to past measures and we validated the particle identification capability of the detector, which ensures an $α$ particle rejection higher than 99.9%, fully satisfying the requirements for CUPID.

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arXiv2021

Search for Double-Beta Decay of $\mathrm{^{130}Te}$ to the $0^+$ States of $\mathrm{^{130}Xe}$ with CUORE

The CUORE experiment is a large bolometric array searching for the lepton number violating neutrino-less double beta decay ($0νββ$) in the isotope $\mathrm{^{130}Te}$. In this work we present the latest results on two searches for the double beta decay (DBD) of $\mathrm{^{130}Te}$ to the first $0^{+}_2$ excited state of $\mathrm{^{130}Xe}$: the $0νββ$ decay and the Standard Model-allowed two-neutrinos double beta decay ($2νββ$). Both searches are based on a 372.5 kg$\times$yr TeO$_2$ 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 $\mathrm{S^{0ν}_{1/2} = 5.6 \times 10^{24} \: \mathrm{yr}}$ for the ${0νββ}$ decay and $\mathrm{S^{2ν}_{1/2} = 2.1 \times 10^{24} \: \mathrm{yr}}$ 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: $\mathrm{(T_{1/2})^{0ν}_{0^+_2} > 5.9 \times 10^{24} \: \mathrm{yr}}$ for the $0νββ$ mode and $\mathrm{(T_{1/2})^{2ν}_{0^+_2} > 1.3 \times 10^{24} \: \mathrm{yr}}$ for the $2νββ$ mode. These represent the most stringent limits on the DBD of $^{130}$Te to excited states and improve by a factor $\sim5$ the previous results on this process.

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arXiv2021

Novel technique for the study of pile-up events in cryogenic bolometers

Precise characterization of detector time resolution is of crucial importance for next-generation cryogenic-bolometer experiments searching for neutrinoless double-beta decay, such as CUPID, in order to reject background due to pile-up of two-neutrino double-beta decay events. In this paper, we describe a technique developed to study the pile-up rejection capability of cryogenic bolometers. Our approach, which consists of producing controlled pile-up events with a programmable waveform generator, has the benefit that we can reliably and reproducibly control the time separation and relative energy of the individual components of the generated pile-up events. The resulting data allow us to optimize and benchmark analysis strategies to discriminate between individual and pile-up pulses. We describe a test of this technique performed with a small array of detectors at the Laboratori Nazionali del Gran Sasso, in Italy; we obtain a 90% rejection efficiency against pulser-generated pile-up events with rise time of ~15ms down to time separation between the individual events of about 2ms.

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arXiv2021

Measurement of the 2$νββ$ Decay Half-life of $^{130}$Te with CUORE

We measured two-neutrino double beta decay of $^{130}$Te using an exposure of 300.7 kg$\cdot$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: $T^{2ν}_{1/2} = 7.71^{+0.08}_{-0.06}\mathrm{(stat.)}^{+0.12}_{-0.15}\mathrm{(syst.)}\times10^{20}$ yr. This measurement is the most precise determination of the $^{130}$Te 2$νββ$ decay half-life to date.

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arXiv2021

New results from the CUORE experiment

The Cryogenic Underground Observatory for Rare Events (CUORE) is the first cryogenic experiment searching for neutrinoless double-beta ($0νββ$) decay that has been able to reach the one-ton scale. The detector, located at the Laboratori Nazionali del Gran Sasso in Italy, consists of an array of 988 TeO$_2$ crystals arranged in a compact cylindrical structure of 19 towers. Following the completion of the detector construction in August 2016, CUORE began its first physics data run in 2017 at a base temperature of about 10 mK. Following multiple optimization campaigns in 2018, CUORE is currently in stable operating mode. In 2019, CUORE released its 2\textsuperscript{nd} result of the search for $0νββ$ with a TeO$_2$ exposure of 372.5 kg$\cdot$yr and a median exclusion sensitivity to a $^{130}$Te $0νββ$ decay half-life of $1.7\cdot 10^{25}$ yr. We find no evidence for $0νββ$ decay and set a 90\% C.I. (credibility interval) Bayesian lower limit of $3.2\cdot 10^{25}$ yr on the $^{130}$Te $0νββ$ decay half-life. In this work, we present the current status of CUORE's search for $0νββ$, as well as review the detector performance. Finally, we give an update of the CUORE background model and the measurement of the $^{130}$Te two neutrino double-beta ($2νββ$) decay half-life.

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arXiv2020

Characterization of cubic Li$_{2}$$^{100}$MoO$_4$ crystals for the CUPID experiment

The CUPID Collaboration is designing a tonne-scale, background-free detector to search for double beta decay with sufficient sensitivity to fully explore the parameter space corresponding to the inverted neutrino mass hierarchy scenario. One of the CUPID demonstrators, CUPID-Mo, has proved the potential of enriched Li$_{2}$$^{100}$MoO$_4$ crystals as suitable detectors for neutrinoless double beta decay search. In this work, we characterised cubic crystals that, compared to the cylindrical crystals used by CUPID-Mo, are more appealing for the construction of tightly packed arrays. We measured an average energy resolution of (6.7$\pm$0.6) keV FWHM in the region of interest, approaching the CUPID target of 5 keV FWHM. We assessed the identification of $α$ particles with and without a reflecting foil that enhances the scintillation light collection efficiency, proving that the baseline design of CUPID already ensures a complete suppression of this $α$-induced background contribution. We also used the collected data to validate a Monte Carlo simulation modelling the light collection efficiency, which will enable further optimisations of the detector.

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arXiv2020

A CUPID Li$_{2}$$^{100}$MoO$_4$ scintillating bolometer tested in the CROSS underground facility

A scintillating bolometer based on a large cubic Li$_{2}$$^{100}$MoO$_4$ crystal (45 mm side) and a Ge wafer (scintillation detector) has been operated in the CROSS cryogenic facility at the Canfranc underground laboratory in Spain. The dual-readout detector is a prototype of the technology that will be used in the next-generation $0\nu2β$ experiment CUPID. The measurements were performed at 18 and 12 mK temperature in a pulse tube dilution refrigerator. This setup utilizes the same technology as the CUORE cryostat that will host CUPID and so represents an accurate estimation of the expected performance. The Li$_{2}$$^{100}$MoO$_4$ bolometer shows a high energy resolution of 6 keV FWHM at the 2615 keV $γ$ line. The detection of scintillation light for each event triggered by the Li$_{2}$$^{100}$MoO$_4$ bolometer allowed for a full separation ($\sim$8$σ$) between $γ$($β$) and $α$ events above 2 MeV. The Li$_{2}$$^{100}$MoO$_4$ crystal also shows a high internal radiopurity with $^{228}$Th and $^{226}$Ra activities of less than 3 and 8 $μ$Bq/kg, respectively. Taking also into account the advantage of a more compact and massive detector array, which can be made of cubic-shaped crystals (compared to the cylindrical ones), this test demonstrates the great potential of cubic Li$_{2}$$^{100}$MoO$_4$ scintillating bolometers for high-sensitivity searches for the $^{100}$Mo $0\nu2β$ decay in CROSS and CUPID projects.

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arXiv2019

Improved Limit on Neutrinoless Double-Beta Decay in $^{130}$Te with CUORE

We report new results from the search for neutrinoless double-beta decay in $^{130}$Te with the CUORE detector. This search benefits from a four-fold increase in exposure, lower trigger thresholds and analysis improvements relative to our previous results. We observe a background of $(1.38\pm0.07)\cdot10^{-2}$ counts$/($keV$\cdot$kg$\cdot$yr$)$ in the $0νββ$ decay region of interest and, with a total exposure of 372.5 kg$\cdot$yr, we attain a median exclusion sensitivity of $1.7\cdot10^{25}$ yr. We find no evidence for $0νββ$ decay and set a $90\%$ CI Bayesian lower limit of $3.2\cdot10^{25}$ yr on the $^{130}$Te 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.

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arXiv2019

Characterization of Light Production and Transport in Tellurium Dioxide Crystals

Simultaneous measurement of phonon and light signatures is an effective way to reduce the backgrounds and increase the sensitivity of CUPID, a next-generation bolometric neutrinoless double-beta decay ($0νββ$) experiment. Light emission in tellurium dioxide (TeO$_2$) crystals, one of the candidate materials for CUPID, is dominated by faint Cherenkov radiation, and the high refractive index of TeO$_2$ complicates light collection. Positive identification of $0νββ$ events therefore requires high-sensitivity light detectors and careful optimization of light transport. A detailed microphysical understanding of the optical properties of TeO$_2$ crystals is essential for such optimization. We present a set of quantitative measurements of light production and transport in a cubic TeO$_2$ crystal, verified with a complete optical model and calibrated against a UVT acrylic standard. We measure the optical surface properties of the crystal, and set stringent limits on the amount of room-temperature scintillation in TeO$_2$ for $β$ and $α$ particles of 5.3 and 8 photons / MeV, respectively, at 90% confidence. The techniques described here can be used to optimize and verify the particle identification capabilities of CUPID.

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arXiv2019

Results of CUORE

The Cryogenic Underground Observatory for Rare Events (CUORE) at the Laboratori Nazionali del Gran Sasso, Italy, is the world's largest bolometric experiment. The detector consists of an array of 988 TeO2 crystals, for a total mass of 742 kg. CUORE is presently in data taking, searching for the neutrinoless double beta decay of 130 Te. CUORE is operational since the spring of 2017. The initial science run already allowed to provide the most stringent limit on the neutrinoless double beta decay half-life of 130Te, and to perform the most precise measurement of the two-neutrino double beta decay half-life. Up to date, we have more than doubled the collected exposure. In this talk, we presenteded the most recent results and discuss the present status of the CUORE experiment.

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arXiv2018

Update on the recent progress of the CUORE experiment

CUORE is a 741 kg array of 988 TeO$_2$ bolometeric crystals designed to search for the neutrinoless double beta decay of $^{130}$Te and other rare processes. CUORE has been taking data since summer 2017, and as of summer 2018 collected a total of 86.3 kg$\cdot$yr of TeO$_2$ exposure. Based on this exposure, we were able to set a limit on the $0νββ$ half-life of $^{130}$Te of $T^{0ν}_{1/2}>1.5\times10^{25}$ yr at 90% C.L. At this conference, we showed the decomposition of the CUORE background and were able to extract a $^{130}$Te $2νββ$ half-life of $T_{1/2}^{2ν}=[7.9\pm0.1 \mathrm{(stat.)}\pm0.2 \mathrm{(syst.)}]\times10^{20}$ yr. This is the most precise measurement of this half-life and is consistent with previous measurements.

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