Study Of Double Beta Decay Research Articles

One-proton transfer reaction for the O18+Ti48 system at 275 MeV

Single-nucleon transfer reactions are processes that selectively probe single-particle components of the populated many-body nuclear states. In this context, recent efforts have been made to build a unified description of the rich nuclear spectroscopy accessible in heavy-ion collisions. An example of this multichannel approach is the study of the competition between successive nucleon transfer and charge exchange reactions, the latter being of particular interest in the context of single and double beta decay studies. To this extent, the one-proton pickup reaction Ti48(O18,F19)Sc47 at 275 MeV was measured for the first time, under the NUMEN experimental campaign. Differential cross-section angular distribution measurements for the F19 ejectiles were performed at INFN-LNS in Catania by using the MAGNEX large acceptance magnetic spectrometer. The data were analyzed within the distorted-wave and coupled-channels Born approximation frameworks. The initial and final-state interactions were described adopting the São Paulo potential, whereas the spectroscopic amplitudes for the projectile and target overlaps were derived from shell-model calculations. The theoretical cross sections are found to be in very good agreement with the experimental data, suggesting the validity of the optical potentials and the shell-model description of the involved nuclear states within the adopted model space.1 MoreReceived 27 May 2021Accepted 8 September 2021DOI:https://doi.org/10.1103/PhysRevC.104.034617©2021 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasDirect reactionsDouble beta decayLow & intermediate energy heavy-ion reactionsNuclear reactionsTransfer reactionsTechniquesOptical, coupled-channel & distorted wave modelsSpectrometers & spectroscopic techniquesNuclear Physics

Cornering (quasi) degenerate neutrinos with cosmology

In light of the improved sensitivities of cosmological observations, we examine the status of quasi-degenerate neutrino mass scenarios. Within the simplest extension of the standard cosmological model with massive neutrinos, we find that quasi-degenerate neutrinos are severely constrained by present cosmological data and neutrino oscillation experiments. We find that Planck 2018 observations of cosmic microwave background (CMB) anisotropies disfavour quasi-degenerate neutrino masses at 2.4 Gaussian σ’s, while adding baryon acoustic oscillations (BAO) data brings the rejection to 5.9σ’s. The highest statistical significance with which one would be able to rule out quasi-degeneracy would arise if the sum of neutrino masses is ∑mv = 60 meV (the minimum allowed by neutrino oscillation experiments); indeed a sensitivity of 15 meV, as expected from a combination of future cosmological probes, would further improve the rejection level up to 17σ. We discuss the robustness of these projections with respect to assumptions on the underlying cosmological model, and also compare them with bounds from β decay endpoint and neutrinoless double beta decay studies.

Storytelling and Science Communication: how to turn (A, Z) → (A, Z + 2) + 2e− + 2v̄e into a story

This outreach workshop explains why narrative structure matters in communicating science to the public. It demonstrates the technique by converting a piece of textbook style introduction to an experiment of underground physics (SNO+’s Double Beta Decay study with 130Te) into a story for the general public.

Double-beta decay and its potential to explore beyond standard model physics

Double-beta decay (DBD) is a rare nuclear process of great interest due to its potential to provide information about physics beyond the Standard Model (BSM). For example, the discovery of the neutrinoless double-beta [Formula: see text] decay mode could give information about important issues such as possible violations of Lorentz symmetry and lepton number, nature of neutrinos (are they Dirac- or Majorana-like particles?), neutrino absolute masses, neutrino mass hierarchy, existence of heavy (sterile) neutrinos, etc. In the theoretical study of DBD, one needs a precise calculation of the nuclear matrix elements (NMEs) and phase space factors (PSFs) entering the half-lives formulas, for different decay modes, transitions and mechanisms of occurrence. Reliable computations of these quantities may result in reliable predictions of DBD half-lives and constrains of the BSM parameters related to the possible mechanisms that can contribute to the [Formula: see text] decay. In this paper, I briefly review the theoretical challenges in the study of [Formula: see text] decay. I describe the computation of the NMEs and PSFs and present results for a number of selected nuclei. Then, I show the broader potential of this process to provide information about BSM physics and present new upper limits for parameters associated with light neutrino, heavy neutrino and SUSY exchange mechanisms. Finally, I suggest a more consistent approach to calculate the NMEs and PSFs, namely to compute directly their product and discuss some possibilities to reduce the errors related to the uncertain value of the axial-vector constant.

Double beta decay searches of 134Xe, 126Xe and 124Xe with large scale Xe detectors

The sensitivity for double beta decay studies of 134Xe and 124Xe is investigated assuming a potential large scale Xe experiment developed for dark matter searches depleted in 136Xe. The opportunity for an observation of the 2νββ - decay of 134Xe is explored for various scenarios. A positive observation should be possible for all calculated nuclear matrix elements. The detection of ECEC of 124Xe can be probed in all scenarios covering the theoretical predicted half-life uncertainties and a potential search for 126Xe is discussed. The sensitivity to decay of 124Xe is discussed and a positive observation might be possible, while decay still remains unobservable. The performed studies take into account solar pp–neutrino interactions, 85Kr beta decay and remaining 136Xe double beta decay as background components in the depleted detector.

Background capabilities of pixel detectors for double beta decay measurements

We discuss the possible use of a progressive detection technique based on pixel detectors for the study of double beta decay (ββ) processes. A series of background measurements in various environments (surface laboratory, underground laboratory, with and without Pb shielding) was performed using the TimePix silicon hybrid pixel device. The pixel detector response to the natural background and intrinsic background properties measured by a low-background HPGe detector are presented.

Study of double beta decay of 48Ca with CANDLES

CANDLES system had proposed for the study of double beta decay of 48Ca by using of undoped CaF2 scintillator. We have constructed CANDLES III detector at sea level. The result of first performance check is described.

Double beta decay study of 48Ca by CaF 2 scintillator

A CaF 2 scintillation detector system (ELEGANT VI) is developed to search for neutrinoless double beta decay (0νDBD) of 48Ca. No events were observed around the Q-value energy region after the analysis of 4.23 kg yr data. To derive the lower limit for the half-life, the expected number of background events was estimated by a Monte Carlo simulation using the measured activities of 214Bi and 220Rn inside CaF 2 crystals. A new lower limit is obtained to be 1.8 × 10 22 yr at the 90% C.L.

Thermal ionization mass spectrometry of molybdenum isotopes

A simple and reliable analytical technique for molybdenum isotope abundance determinations by thermal ionization mass spectrometry, capable of realizing precise data from submicrogram amounts of material, is described. This method was specifically designed for molybdenum fission product and double-beta decay studies, for which only nanogram amounts of sample are available. The molybdenum isotope composition of a high purity molybdenum metal rod, four off-the-shelf reagents, and five molybdenites from different regions were analyzed. No significant isotope abundance variations were observed. The molybdenum isotope abundances determined were compared to current International Union of Pure and Applied Chemistry (IUPAC) isotope composition and atomic weight data.

Nuclear structure studies with (p, n) reactions at intermediate energies

The (p, n) reaction at intermediate energies is predominantly impulsive and single-step. The distorted-wave impulse approximation (DWIA) with realistic, large-basis shell-model wavefunctions is able to describe strong transitions accurately, including polarization observables. The 48Ca(p, n) 48Sc reaction is discussed as an example including different kinds of one-particle one-hole (1p1h) excitations. Because the (p, n) reaction proceeds by a simple mechanism which can generally be described theoretically, it provides an important tool for studying nuclear structure. Applications of such studies include double beta-decay studies, nuclear astrophysics, and specific issues in nuclear physics.

Search for ββ decay of 96Zr to excited states of 96Mo

We have performed an experimental study of double beta decay of 96Zr to excited states in 96Mo by means of a HPGe detector. New limits on the half-lives of these particular decays have been obtained, ranging between 2 × 10 19 yr and 4 × 10 19 yr (90%C.L.). In addition, the single beta decay half-life of 96Zr has been established to be ≥3.8 × 10 19 yr. Preliminary results on 150Nd double beta decay to excited states in 150Sm are also reported.

Large calorimetric devices for double beta decay and dark matter

The use of cryogenic thermal particle detectors permits the realization of detectors of various compositions, various sizes and very good energy resolution. In particular these characteristics are very promising for the realization of double beta decay and dark matter search experiments. Our group is mainly interested in the study of double beta decay of 130Te and 116Cd. For tellurium we have realized various detectors using TeO 2 crystals, the final one with a mass of 334 g. For cadmium a CdWO 4 crystal of 58 g has been used in various tests. The double beta decay measurement has been performed in the Gran Sasso Underground Laboratory. Measurements on the 334 g TeO 2 crystal have been performed for 3000 h. Detector resolution is around 10 keV FWHM and the internal contamination of 238U and 232Th in the crystal is of the order of 10 −13 g/g. A lower limit on the half-life of neutrinoless double beta decay for 130Te of 8.2 × 10 21 yr (90% CL) is measured. The test measurements of CdWO 4 reach an energy resolution of about 5 keV FWHM with a very high efficiency to gamma ray detection. A limit on the neutrinoless channel of 7 × 10 19 yr (90% CL) is evaluated in 340 h. In this test an end point energy of 318.8 ± 1.4 ± 5 keV and a half-life of (9.3 ± 0.5 ± 1) × 10 15 yr for the beta decay of 113Cd are also measured. The last part of the paper is dedicated to a brief discussion of our proposal for the solar neutrino flux measurement and for the search of dark matter using cryogenic detectors.

A comparative study of double beta decay by shell model and quasiparticle RPA

Nuclear matrix elements of the two-neutrino and neutrinolessββ decays of48Ca(0 g.s. + )→48Ti(0 g.s. + ) are calculated by shell model and QRPA. The two-neutrino matrix elementM GT 2v is rather reliably evaluated in the QRPA approach by a careful fit of the particle-particle interaction strength in the 1+ channel, which governs the spinisospin ground-state correlations. The shell-model value ofM GT 2v depends not only on the 1+ interaction but largely on the pairing and quadrupole interactions. Concerning the neutrinoless-mode nuclear matrix elements, the shell model gives generally smaller values than the QRPA. A detailed analysis indicates that the discrepancies originate mainly from the truncation of shell-model configurations (fp-space). The QRPA calculation in a larger model space well takes into account transitions from/to single-particle orbits far from the Fermi surface, and those transitions give rise to sizable contributions because of large momentum transfers due to the exchange of a virtual neutrino.

Electronic instrumentation for research in elementary particle physics and cosmic rays at Hong Kong

Work being carried out at the University of Hong Kong on the following is summarized briefly: (1) design and construction of a 50-channel pulse height analyzer, (2) design and construction of the electronic gear for the study of double BETA decay,(3) construction of a composite 5-tray cosmic-ray counter telescope and the associated electronic system, and (4) design of electronic gear for the study of extensive air showers. (A.G.W.)

On the probability of double beta decay

Double beta decay is discussed in relation to parity non-conservation. Two possible ways of neutrino-less double beta decay (allowed and forbidden) are investigated and the half-life of decay is calculated. For allowed transitions we obtain for Ca48 an estimatedT1/2=2×1019 years. The negative results of the experiments by Lukjanov et al., who give the valueT1/2=0.7×1019 years for the lower limit of the half-life of double beta decay of Ca48, cannot therefore be regarded as a definitive solution of the question, whether the neutrino is a Dirac or Majorana particle. Further study of double beta decay, aimed at finding higher values of the lower limit of half-life, are of considerable importance for theory.