arXiv subjects

A. Neacsu

Publications and source records attributed to A. Neacsu.

3 recordsLinked to original sources

arXiv2026

Direct Calculation of the Two-Neutrino Double-Beta Decay Rate Including the Full Lepton-Energy Dependence

The calculation of the two-neutrino double-beta decay (DBD) rates has so far relied on approximations that decouple the nuclear structure from the emitted lepton kinematics. To ensure a more rigorous treatment, we propose an approach which incorporates the full interdependence between nuclear structure and lepton kinematics within a unified formula and performs calculations without resorting to these approximations. Deviations of the decay rates and electron spectra from the traditional methods, such as closure, non-closure, and Taylor expansion approximations, are presented and discussed for the isotopes $^{82}$Se and $^{136}$Xe. Our approach gives a more realistic description of the DBD process and paves the way for further theoretical and experimental investigations into the correlated nuclear structure interplay with emitted lepton kinematics contributing to the dynamics of the process. Extensions of this framework to other isotopes and to neutrinoless double-beta decay are currently underway.

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arXiv2022

A Statistical Analysis for the Neutrinoless Double-Beta Decay Matrix element of 48Ca

Neutrinoless double beta decay ($0νββ$) nuclear matrix elements (NME) are the object of many theoretical calculation methods, and are very important for analysis and guidance of a large number of experimental efforts. However, there are large discrepancies between the NME values provided by different methods. In this paper we propose a statistical analysis of the $^{48}$Ca $0νββ$ NME using the interacting shell model, emphasizing the range of the NME probable values and its correlations with observables that can be obtained from the existing nuclear data. Based on this statistical analysis with three independent effective Hamiltonians we propose a common probability distribution function for the $0νββ$ NME, which has a range of (0.45 - 0.95) at 90\% confidence level of, and a mean value of 0.68.

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arXiv2019

Neutrinoless double-$β$ decay of $^{124}$Sn, $^{130}$Te, and $^{136}$Xe in the Hamiltonian-based generator-coordinate method

We present a generator-coordinate method for realistic shell-model Hamiltonians that closely approximates the full shell model calculations of the matrix elements for the neutrinoless double-$β$ decay of $^{124}$Sn, $^{130}$Te, and $^{136}$Xe. We treat not only quadrupole deformations but also the proton-neutron pairing amplitudes as generator coordinates. We validate this method by calculating and comparing spectroscopic quantities with the exact shell model results and experimental data. Our Hamiltonian-based generator-coordinate method produces $0νββ$ matrix elements much closer to the shell model ones, compared to the existing energy-density-functional-based generator-coordinate approaches. The remaining overestimation of $0νββ$ nuclear matrix element suggests that additional correlations may be needed to be taken into account for $^{124}$Sn, $^{130}$Te, and $^{136}$Xe when calculating with the Hamiltonian-based generator-coordinate method. The validation of this method may open the possibility of calculating $0νββ$ matrix element of $^{150}$Nd in a large shell-model space.

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