Search results for "Double beta"
showing 10 items of 320 documents
Supersymmetry and neutrinoless double beta decay.
1996
Neutrinoless double beta decay ($\znbb$) induced by superparticle exchange is investigated. Such a supersymmetric (SUSY) mechanism of $\znbb$ decay arises within SUSY theories with R-parity non-conservation (\rp). We consider the minimal supersymmetric standard model (MSSM) with explicit \rp terms in the superpotential (\rp MSSM). The decay rate for the SUSY mechanism of $\znbb$ decay is calculated. Numerical values for nuclear matrix elements for the experimentally most interesting isotopes are calculated within pn-QRPA. Constraints on the \rp MSSM parameter space are extracted from current experimental half-life limits. The most stringent limits are derived from data on $^{76}$Ge. It is s…
Relating quarks and leptons with the T7 flavour group
2015
In this letter we present a model for quarks and leptons based on T7 as flavour symmetry, predicting a canonical mass relation between charged leptons and down-type quarks proposed earlier. Neutrino masses are generated through a Type-I seesaw mechanism, with predicted correlations between the atmospheric mixing angle and neutrino masses. Compatibility with oscillation results lead to lower bounds for the lightest neutrino mass as well as for the neutrinoless double beta decay rates, even for normal neutrino mass hierarchy.
Single and Double Beta-DecayQValues among the TripletZr96,Nb96, andMo96
2016
The atomic mass relations among the mass triplet ^{96}Zr, ^{96}Nb, and ^{96}Mo have been determined by means of high-precision mass measurements using the JYFLTRAP mass spectrometer at the IGISOL facility of the University of Jyvaskyla. We report Q values for the ^{96}Zr single and double β decays to ^{96}Nb and ^{96}Mo, as well as the Q value for the ^{96}Nb single β decay to ^{96}Mo, which are Q_{β}(^{96}Zr)=163.96(13), Q_{ββ}(^{96}Zr)=3356.097(86), and Q_{β}(^{96}Nb)=3192.05(16) keV. Of special importance is the ^{96}Zr single β-decay Q value, which has never been determined directly. The single β decay, whose main branch is fourfold unique forbidden, is an alternative decay path to the…
Radon and material radiopurity assessment for the NEXT double beta decay experiment
2015
Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UAM
Possible detection of the doubleβ+/electron-capture decay
1993
The two-neutrino double [beta] decay matrix elements of [sup 58]Ni, [sup 96]Ru, [sup 106]Cd, and [sup 136]Ce are calculated in the framework of the quasiparticle random phase approximation and the corresponding double [beta][sup +]/electron-capture (EC) decay ([beta][sup +][beta][sup +]/[beta][sup +]EC/ECEC) half-lives are estimated. The calculated ground-state-to-ground-state half-lives range from 3.9[times]10[sup 23] to 6.4[times]10[sup 19] yr indicating that the double [beta][sup +]/EC decay could, in principle, be detected using currently known experimental techniques.
Double β Decay and the Axial Strength
2019
Quenching of the weak axial strength gA is discussed and relations of this quenching to the nuclear matrix elements of double beta decays are highlighted. An analysis of Gamow-Teller transitions in the mass range A = 62 − 142 is presented and its results are compared with those of many previous works. The enhancement of the axial charge is discussed for first-forbidden pseudoscalar β transitions. Higher-forbidden β transitions are introduced and their role in determining the effective value of gA is examined, in particular from the point of view of the β-decay half-lives and the shapes of electron spectra of forbidden non-unique β transitions. peerReviewed
NURE: An ERC project to study nuclear reactions for neutrinoless double beta decay
2017
Neutrinoless double beta decay (0{\nu}\b{eta}\b{eta}) is considered the best potential resource to determine the absolute neutrino mass scale. Moreover, if observed, it will signal that the total lepton number is not conserved and neutrinos are their own anti-particles. Presently, this physics case is one of the most important research beyond Standard Model and might guide the way towards a Grand Unified Theory of fundamental interactions. Since the \b{eta}\b{eta} decay process involves nuclei, its analysis necessarily implies nuclear structure issues. The 0{\nu}\b{eta}\b{eta} decay rate can be expressed as a product of independent factors: the phase-space factors, the nuclear matrix elemen…
Value of the Axial-Vector Coupling Strength in β and ββ Decays : A Review
2017
In this review the quenching of the weak axial-vector coupling constant, $g_{\rm A}$, is discussed in nuclear $\beta$ and double-$\beta$ decays. On one hand, the nuclear-medium and nuclear many-body effects are separated, and on the other hand the quenching is discussed from the points of view of different many-body methods and different $\beta$-decay and double-$\beta$-decay processes. Both the historical background and the present status are reviewed and contrasted against each other. The theoretical considerations are tied to performed and planned measurements, and possible new measurements are urged, whenever relevant and doable. Relation of the quenching problem to the measurements of …
Double beta decays of 124Xe investigated in the QRPA framework
2013
The two-neutrino (2ν2β) and neutrinoless (0ν2β) double beta decays of 124Xe are investigated. Decays to the ground state, , and various 0+ and 2+ excited states in 124Te are considered. The corresponding nuclear matrix elements have been calculated by using the quasiparticle random-phase approximation combined with the multiple-commutator model. G-matrix-based effective nuclear interactions have been used in realistic single-particle model spaces. All possible channels, β+β+, β+EC, and ECEC, are discussed for both the 2ν2β and 0ν2β decays. The associated half-lives are computed, in particular the one corresponding to the resonant neutrinoless double electron capture transition to the 2790.4…
Total Absorption Spectroscopy Study ofRb92Decay: A Major Contributor to Reactor Antineutrino Spectrum Shape
2015
The antineutrino spectra measured in recent experiments at reactors are inconsistent with calculations based on the conversion of integral beta spectra recorded at the ILL reactor. (92)Rb makes the dominant contribution to the reactor antineutrino spectrum in the 5-8 MeV range but its decay properties are in question. We have studied (92)Rb decay with total absorption spectroscopy. Previously unobserved beta feeding was seen in the 4.5-5.5 region and the GS to GS feeding was found to be 87.5(25)%. The impact on the reactor antineutrino spectra calculated with the summation method is shown and discussed.