Search results for " Beta Decay"
showing 10 items of 323 documents
Searches for neutrinoless resonant double electron captures at LNGS
2012
Several experiments were performed during last years at underground (3600 m w.e.) Laboratori Nazionali del Gran Sasso (LNGS) of the INFN (Italy) to search for resonant 2$\varepsilon0\nu$ captures in 96Ru, 106Cd, 136Ce, 156Dy, 158Dy, 180W, 184Os, 190Pt with the help of HP Ge semiconductor detectors, and ZnWO4 and 106CdWO4 crystal scintillators. No evidence for r-2$\varepsilon0\nu$ decays was found, and only T_{1/2} limits were established in the range of 10^{14}-10^{21} yr.
High-frequency Ramsey excitation in a Penning trap
2007
The Ramsey excitation method for high-precision mass-measurements of highly-charged ions has been investigated and benchmarked using H2+ ions in the Penning-trap mass-spectrometer SMILETRAP. The reason for using H2+ ions are their high cyclotron frequency which is typical for the highly-charged ions usually used at SMILETRAP. Two-, three- and four-pulse Ramsey excitation data are analyzed with the help of recent theoretical work and are compared with the previously used single-pulse excitation data. An improvement factor of 2.9 in the statistical uncertainty is achieved. Furthermore the mass of 76Se, included in the previous Q-value measurement of the 76Ge neutrinoless double beta decay, is…
Role of Single-Particle Energies in Microscopic Interacting Boson Model Double Beta Decay Calculations
2021
Single-particle level energies form a significant input in nuclear physics calculations where single-particle degrees of freedom are taken into account, including microscopic interacting boson model investigations. The single-particle energies may be treated as input parameters that are fitted to reach an optimal fit to the data. Alternatively, they can be calculated using a mean field potential, or they can be extracted from available experimental data, as is done in the current study. The role of single-particle level energies in the microscopic interacting boson model calculations is discussed with special emphasis on recent double beta decay calculations.
Occupation probabilities of single particle levels using the microscopic interacting boson model: Application to some nuclei of interest in neutrinol…
2016
We have developed a new method to calculate the occupancies of single particle levels in atomic nuclei. This method has been developed in the context of the microscopic interacting boson model, in which neutron and proton degrees of freedom are treated explicitly. The energies of the single particle levels constitute a very important input for the calculation of the occupancies in this method. In principle these energies can be considered as input parameters that can be fitted to reproduce the experimental occupancies. Instead of fitting, in this study we have extracted the single particle energies from experimental data on nuclei with a particle more or one particle less than a shell closu…
Neutrinoless double beta decay and QCD running at low energy scales
2018
There is a common belief that the main uncertainties in the theoretical analysis of neutrinoless double beta ($0\nu\beta\beta$) decay originate from the nuclear matrix elements. Here, we uncover another previously overlooked source of potentially large uncertainties stemming from non-perturbative QCD effects. Recently perturbative QCD corrections have been calculated for all dimension 6 and 9 effective operators describing $0\nu\beta\beta$-decay and their importance for a reliable treatment of $0\nu\beta\beta$-decay has been demonstrated. However, these perturbative results are valid at energy scales above $\sim 1$ GeV, while the typical $0\nu\beta\beta$-scale is about $\sim 100$ MeV. In vi…
Neutrino masses and mixing: a flavour symmetry roadmap
2012
Over the last ten years tri-bimaximal mixing has played an important role in modeling the flavour problem. We give a short review of the status of flavour symmetry models of neutrino mixing. We concentrate on non-Abelian discrete symmetries, which provide a simple way to account for the TBM pattern. We discuss phenomenological implications such as neutrinoless double beta decay, lepton flavour violation as well as theoretical aspects such as the possibility to explain quarks and leptons within a common framework, such as grand unified models
The neutrinoless double beta decay of 76Ge, 82Se, 86Kr, 114Cd, 128, 130Te and 134, 136Xe in the framework of a relativistic quark confinement model
1991
The half-life of the 0+ → 0+ neutrinoless double beta decay is calculated for 76Ge, 82Se, 86Kr, 114Cd, 128, 130Te and 134, 136Xe and the upper limit for the effective neutrino mass of 3.0 eV is deduced from available experimental data. In addition, the contribution of the right-handed charged weak currents to the effective weak hamiltonian is estimated. The relevant parameters attain the values |〈Λ〉| < 4.1 × 10−6 and |〈ν〉| < 6.6 × 10−8. The nucleonic weak current is treated starting from the current quark level and evaluating the quark current using relativistic quark wave functions obtained from a Dirac equation with a harmonic confinement potential. The nuclear matrix elements of the thus…
Neutrinoless double beta decay in the dualized standard model
2001
The Dualized Standard Model offers a {\it raison d'\^etre} for 3 fermion generations and an explanation for their distinctive mass and mixing patterns, reproducing to a reasonable accuracy the empirical mixing matrix and mass spectrum for both quarks and leptons in terms of just a few parameters. With its parameters thus fixed, the result is a highly predictive framework. In particular, it is shown that it gives explicit parameter-free predictions for neutrinoless double beta decays. For $^{76}Ge$, it predicts a half-life of $10^{28}-10^{30}$ years, which satisfies the present experimental lower bound of $1.8 \times 10^{25}$ years.
New leptoquark mechanism of neutrinoless double beta decay
1996
A new mechanism for neutrinoless double beta ($\znbb$) decay based on leptoquark exchange is discussed. Due to the specific helicity structure of the effective four-fermion interaction this contribution is strongly enhanced compared to the well-known mass mechanism of $\znbb$ decay. As a result the corresponding leptoquark parameters are severely constrained from non-observation of $\znbb$-decay. These constraints are more stringent than those derived from other experiments.
Confined quarks and the neutrinoless ββ decay
1990
Abstract The half life of the neutrinoless double beta decay of 76Ge into the ground state of 76Se is calculated in a relativistic quark confinement model. The neutron-proton quasi-particle random phase approximation is used to evaluate the nuclear matrix elements involved in the decay amplitude. We avoid the closure approximation, but compare our results with this approximation. From the experimental half life we deduce an upper limit for the Majorana mass of the neutrino and estimate the right-handed contribution to the charged weak current.