Search

The double beta decay of 150Nd to the first excited 0+ level of 150Sm (Eexc = 740.5 keV) has been investigated with the help of the ultra-low-background setup consisting of four HP Ge (high-purity germanium) detectors (≃225 cm3 volume each one) at the Gran Sasso underground laboratory of INFN (Italy). A highly purified 2.381-kg sample of neodymium oxide (Nd2O3) was used as a source of γ quanta expected in the decays. Gamma quanta with energies 334.0 keV and 406.5 keV emitted after dEexcitation of the 01 + 740.5 keV level of 150Sm are observed in the coincidence spectra accumulated over 16375 h. The half-life relatively to the two neutrino double beta decay 150Nd 150Sm(01+) is measured as T1/2 =[4.7+4.1-1.9(stat)±0.5(syst)]·1019 y, in agreement with results of previous experiments. [ABSTRACT FROM AUTHOR]

The first phase of the Advanced Mo-based Rare process Experiment (AMoRE-I), an experimental search for neutrinoless double beta decay (0νββ) of 100Mo in calcium molybdate (40Ca100MoO4) crystal using cryogenic detection techniques, is in preparation at the YangYang underground laboratory (Y2L) in Korea. A GEANT4 based Monte Carlo simulation was performed for the first-phase AMoRE detector and shield configuration. Background sources such as 238U, 232Th, 235U, and 210Pb from inside the crystals, surrounding materials, outer shielding walls of the Y2L cavity were simulated. The estimated background rate in the region of interest was estimated to be <1.5x10-3 counts/keV/kg/yr (ckky). The effects of random coincidences between backgrounds and two-neutrino double beta decays of 100Mo as a potential background source were estimated to be <2.3x10-4 ckky. [ABSTRACT FROM AUTHOR]

Random coincidences of nuclear events can be one of the main background sources in low-temperature calorimetric experiments looking for neutrinoless doublebeta decay, especially in those searches based on scintillating bolometers embedding the promising double-beta candidate 100 Mo, because of the relatively short half-life of the twoneutrino double-beta decay of this nucleus. We show in this work that randomly coinciding events of the two-neutrino double-beta decay of 100 Mo in enriched Li2100 MoO4 detectors can be effectively discriminated by pulse-shape analysis in the light channel if the scintillating bolometer is provided with a Neganov-Luke light detector, which can improve the signal-to-noise ratio by a large factor, assumed here at the level of~750 on the basis of preliminary experimental results obtained with these devices. The achieved pile-up rejection efficiency results in a very low contribution, of the order of ~6 × 10-5 counts/(keV·kg·y), to the background counting rate in the region of interest for a large volume (~90 cm³) Li2100 MoO4 detector. This background level is very encouraging in view of a possible use of the Li2100 MoO4 solution for a bolometric tonne-scale next-generation experiment as that proposed in the CUPID project. [ABSTRACT FROM AUTHOR]

Development of low radioactive technique allows to investigate many other rare nuclear and subnuclear processes: double decay, rare and decays, and to search for hypothetical particles and processes like axions, charge nonconserving decays, the nucleon, di-nucleon and tri-nucleon decays into invisible channels, to test the Pauli principle. Here, we present results of the rare processes searches and development of instrumentation for low counting experiments. [ABSTRACT FROM AUTHOR]

An experiment to search for double-β decay processes in 96Ru and 104Ru, which are accompanied by γ rays, has been realized in the underground Gran Sasso National Laboratories of the I.N.F.N. (Italy). Ruthenium samples with masses of ≈0.5-0.7 kg were measured with the help of ultralow-background high-purity Ge γ-ray spectrometry. After 2162 h of data taking the samples were deeply purified to reduce the internal contamination of 40K. The last part of the data has been accumulated over 5479 h. New improved half-life limits on 2β+/ɛβ+/2ɛ processes in 96Ru have been established on the level of 1020 yr, in particular for decays to the ground state of 96Mo: T1/22ν2β+≥1.4×1020 yr, T1/22νɛβ+≥8.0×1019 yr, and T1/20ν2K≥1.0×1021 yr (all limits are at 90% C.L.). The resonant neutrinoless double-electron captures to the 2700.2 and 2712.7 keV excited states of 96Mo are restricted as T1/20νKL≥2.0×1020 yr and T1/20ν2L≥3.6×1020 yr, respectively. Various two-neutrino and neutrinoless 2β half-lives of 96Ru have been estimated in the framework of the quasiparticle random-phase approximation approach. In addition, the T1/2 limit for 0ν2β- transitions of 104Ru to the first excited state of 104Pd has been set as ≥6.5×1020 yr. [ABSTRACT FROM AUTHOR]

The α decays of naturally occurring platinum isotopes, which are accompanied by the emission of γ quanta, have been searched for deep underground (3600 m water equivalent) at the Gran Sasso National Laboratories of the INFN (Italy). A sample of Pt with a mass of 42.5 g and a natural isotopic composition has been measured with a low background HP Ge detector (468 cm3) during 1815 h. The α decay of 190Pt to the first excited level of 186Os (Jπ=2+, Eexc=137.2 keV) has been observed for the first time, with the half-life determined as T1/2=2.6-0.3+0.4(stat.)±0.6(syst.)×1014 yr. The T1/2 limits for the α decays of other Pt isotopes have been determined at the level of T1/2≂1016-1020 yr. These limits have been set for the first time or they are better than those known from earlier experiments. [ABSTRACT FROM AUTHOR]

Studies of the 2β decay of 116Cd, 180W and 186W have been performed in the Solotvina Underground Laboratory with the help of the super-low background 116CdWO4 crystal scintillators. The half-life value of the two-neutrino 2β decay of 116Cd has been revised as T1/22ν=2.9±0.1(stat)−0.3+0.4(syst)×1019 yr. Besides, the new half-live limits on different modes of this process have been established for two natural tungsten isotopes, in particular, T1/2≥1.0 (1.6)×1021 yr at 90% (68%) C.L. for the neutrinoless 2β decay of 186W to the ground (0+) and first excited (2+) level of 186Os. [Copyright &y& Elsevier]

The coincidence technique can offer a useful way to investigate β and ββ decay processes in 48Ca. In this paper the results of a preliminary experimental search are presented. In particular, here the first experimental limit on the half life of the ββ2ν(0+–2+) decay of 48Ca has been obtained; it is T1/2>1.2×1018 y (90% C.L.). [Copyright &y& Elsevier]

Data collected during 637 days in the Baksan Neutrino Observatory with 1 kg high purity Ge semiconductor detector have been analyzed to search for charge non-conserving β decay of 73Ge. It is the first real-time experiment, in which one of the best up-to-date life time limits has been established for this process as: τCNC (73Ge→73As)>2.6×1023 yr at 90% C.L. [Copyright &y& Elsevier]

A radiopure cadmium tungstate crystal scintillator, enriched in 106Cd to 66%, with mass of 216 g (106CdWO4), was used to search for double-β decay processes in 106Cd in coincidence with four ultra-low-background high-purity germanium detectors in a single cryostat. Improved limits on the double-β processes in 106Cd have been set on the level of 1020-1021 yr after 13 085 h of data taking. In particular, the half-life limit on the two-neutrino electron capture with positron emission, T2νɛβ+1/2≥1.1×1021 yr, has reached the region of theoretical predictions. With this half-life limit the effective nuclear matrix element for the 2νɛβ+ decay is bounded as M2νɛβ+eff≤1.1. The resonant neutrinoless double-electron captures to the 2718-, 2741-, and 2748-keV excited states of 106Pd are restricted at the level of T1/2≥(8.5×1020-1.4×1021) yr. [ABSTRACT FROM AUTHOR]

Neutrinoless double beta decay (0νββ) is a yet unobserved nuclear process that would demonstrate Lepton number violation, a clear evidence of beyond standard model physics. The process two neutrino double beta decay (2νββ) is allowed by the standard model and has been measured in numerous experiments. In this Letter, we report a measurement of 2νββ decay half-life of ^{100}Mo to the ground state of ^{100}Ru of [7.07±0.02(stat)±0.11(syst)]×10^{18}  yr by the CUPID-Mo experiment. With a relative precision of ±1.6% this is the most precise measurement to date of a 2νββ decay rate in ^{100}Mo. In addition, we constrain higher-order corrections to the spectral shape, which provides complementary nuclear structure information. We report a novel measurement of the shape factor ξ&#95;{3,1}=0.45±0.03(stat)±0.05(syst) based on a constraint on the ratio of higher-order terms from theory, which can be reliably calculated. This is compared to theoretical predictions for different nuclear models. We also extract the first value for the effective axial vector coupling constant obtained from a spectral shape study of 2νββ decay.

Core-collapse Supernovae (SNe) are one of the most energetic events in the Universe, during which almost all the star's binding energy is released in the form of neutrinos. These particles are direct probes of the processes occurring in the stellar core and provide unique insights into the gravitational collapse. RES-NOVA will revolutionize how we detect neutrinos from astrophysical sources, by deploying the first ton-scale array of cryogenic detectors made from archaeological lead. Pb offers the highest neutrino interaction cross-section via coherent elastic neutrino-nucleus scattering (CEνNS). Such process will enable RES-NOVA to be equally sensitive to all neutrino flavours. For the first time, we propose the use archaeological Pb as sensitive target material in order to achieve an ultra-low background level in the region of interest (O(1 keV)). All these features make possible the deployment of the first cm-scale neutrino telescope for the investigation of astrophysical sources. In this contribution, we will characterize the radiopurity level and the performance of a small-scale proof-of-principle detector of RES-NOVA, consisting in a PbWO 4 crystal made from archaeological-Pb operated as cryogenic detector., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Neutrinoless double beta decay (0νββ) processes sample a wide range of intermediate forbidden nuclear transitions, which may be impacted by quenching of the axial vector coupling constant (g&#95;{A}/g&#95;{V}), the uncertainty of which plays a pivotal role in determining the sensitivity reach of 0νββ experiments. In this Letter, we present measurements performed on a high-resolution LiInSe&#95;{2} bolometer in a "source=detector" configuration to measure the spectral shape of the fourfold forbidden β decay of ^{115}In. The value of g&#95;{A}/g&#95;{V} is determined by comparing the spectral shape of theoretical predictions to the experimental β spectrum taking into account various simulated background components as well as a variety of detector effects. We find evidence of quenching of g&#95;{A}/g&#95;{V} at >5σ with a model-dependent quenching factor of 0.655±0.002 as compared to the free-nucleon value for the interacting shell model. We also measured the ^{115}In half-life to be [5.18±0.06(stat)&#95;{-0.015}^{+0.005}(sys)]×10^{14}  yr within the interacting shell model framework. This Letter demonstrates the power of the bolometeric technique to perform precision nuclear physics single-β decay measurements, which along with improved nuclear modeling can help reduce the uncertainties in the calculation of several decay nuclear matrix elements including those used in 0νββ sensitivity calculations.

The CUPID-Mo experiment at the Laboratoire Souterrain de Modane (France) is a demonstrator for CUPID, the next-generation ton-scale bolometric 0νββ experiment. It consists of a 4.2 kg array of 20 enriched Li&#95;{2}^{100}MoO&#95;{4} scintillating bolometers to search for the lepton-number-violating process of 0νββ decay in ^{100}Mo. With more than one year of operation (^{100}Mo exposure of 1.17  kg×yr for physics data), no event in the region of interest and, hence, no evidence for 0νββ is observed. We report a new limit on the half-life of 0νββ decay in ^{100}Mo of T&#95;{1/2}>1.5×10^{24}  yr at 90% C.I. The limit corresponds to an effective Majorana neutrino mass ⟨m&#95;{ββ}⟩<(0.31-0.54)  eV, dependent on the nuclear matrix element in the light Majorana neutrino exchange interpretation.

We report the results of a first experimental search for lepton number violation by four units in the neutrinoless quadruple-β decay of ^{150}Nd using a total exposure of 0.19 kg yr recorded with the NEMO-3 detector at the Modane Underground Laboratory. We find no evidence of this decay and set lower limits on the half-life in the range T&#95;{1/2}>(1.1-3.2)×10^{21}  yr at the 90% C.L., depending on the model used for the kinematic distributions of the emitted electrons.

The BiPo-3 detector is a low radioactive detector dedicated to measuring ultra-low natural contaminations of 208 Tl and 214 Bi in thin materials, initially developed to measure the radiopurity of the double β decay source foils of the SuperNEMO experiment at the μBq/kg level. The BiPo-3 technique consists in installing the foil of interest between two thin ultra-radiopure scintillators coupled to low radioactive photomultipliers. The design and performances of the detector are presented. In this paper, the final results of the 208 Tl and 214 Bi activity measurements of the first enriched 82 Se foils are reported for the first time, showing the capability of the detector to reach sensitivities in the range of some μBq/kg., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

This paper reports on the development of a technology involving 100 Mo -enriched scintillating bolometers, compatible with the goals of CUPID, a proposed next-generation bolometric experiment to search for neutrinoless double-beta decay. Large mass ( ∼ 1 kg ), high optical quality, radiopure 100 Mo -containing zinc and lithium molybdate crystals have been produced and used to develop high performance single detector modules based on 0.2-0.4 kg scintillating bolometers. In particular, the energy resolution of the lithium molybdate detectors near the Q -value of the double-beta transition of 100 Mo (3034 keV) is 4-6 keV FWHM. The rejection of the α -induced dominant background above 2.6 MeV is better than 8 σ . Less than 10 μ Bq/kg activity of 232 Th ( 228 Th ) and 226 Ra in the crystals is ensured by boule recrystallization. The potential of 100 Mo -enriched scintillating bolometers to perform high sensitivity double-beta decay searches has been demonstrated with only 10 kg × d exposure: the two neutrino double-beta decay half-life of 100 Mo has been measured with the up-to-date highest accuracy as T 1 / 2 = [6.90 ± 0.15(stat.) ± 0.37(syst.)] × 10 18 years . Both crystallization and detector technologies favor lithium molybdate, which has been selected for the ongoing construction of the CUPID-0/Mo demonstrator, containing several kg of 100 Mo ., (© The Author(s) 2017.)

We report results from the NEMO-3 experiment based on an exposure of 1275 days with 661 g of (130)Te in the form of enriched and natural tellurium foils. The ββ decay rate of (130)Te is found to be greater than zero with a significance of 7.7 standard deviations and the half-life is measured to be T(½)(2ν) = [7.0 ± 0.9(stat) ± 1.1(syst)] × 10(20) yr. This represents the most precise measurement of this half-life yet published and the first real-time observation of this decay.