0000000000962343
AUTHOR
F. Iachello
Nuclear physics of non-standard 0νβ β-decay
The observation neutrinoless double beta (0νβ β) decay remains crucial for understanding lepton number violation. In view of the difficulties to observe the mass mechanism of 0νβ β-decay, investigations of other mechanisms are in order. These non-standard mechanisms can be divided into short-range and long-range mechanisms. Recently, we have started systematic study for all possible short-range and long-range non-standard mechanisms. The aim of this study is twofold: I) to provide explicit formulas for the nuclear matrix elements (NMEs) and phase-space factors (PSFs) from which the decay rate for one or a combination of mechanisms operating at the same time can be calculated; II) to provide…
Nuclear matrix elements for Majoron-emitting double-β decay
A complete calculation of the nuclear matrix elements (NME) for Majoron emitting neutrinoless double beta decay within the framework of IBM-2 for spectral indices n=1,3,7 is presented. By combining the results of this calculation with previously calculated phase space factors (PSF) we give predictions for expected half-lives. By comparing with experimental limits on the half-lives we set limits on the coupling constants ⟨gMee⟩ of all proposed Majoron-emitting models. peerReviewed
Phase-space factors and half-life predictions for Majoron-emitting β−β− decay
A complete calculation of phase space factors (PSFs) for Majoron-emitting 0νβ − β − decay modes is presented. The calculation makes use of exact Dirac wave functions with finite nuclear size and electron screening and includes lifetimes, single-electron spectra, summed electron spectra, and angular electron correlations. Combining these results with recent microscopic interacting boson model nuclear matrix elements (NMEs) we make half-life predictions for the ordinary Majoron decay (spectral index n=1 ). Furthermore, comparing theoretical predictions with the obtained experimental lower bounds for this decay mode we are able to set limits on the effective Majoron-neutrino coupling constant …
Phase space factors and half-life predictions for Majoron emitting $\beta^-\beta^-$ decay
A complete calculation of phase space factors (PSF) for Majoron emitting $0\nu\beta^-\beta^-$ decay modes is presented. The calculation makes use of exact Dirac wave functions with finite nuclear size and electron screening and includes life-times, single electron spectra, summed electron spectra, and angular electron correlations. Combining these results with recent interacting boson nuclear matrix elements (NME) we make half-life predictions for the the ordinary Majoron decay (spectral index $n$=1). Furthermore, comparing theoretical predictions with the obtained experimental lower bounds for this decay mode we are able to set limits on the effective Majoron-neutrino coupling constant $\l…
0νββ and 2νββ nuclear matrix elements in the interacting boson model with isospin restoration
We introduce a method for isospin restoration in the calculation of nuclear matrix elements (NMEs) for 0νββ and 2νββ decay within the framework of the microscopic interacting boson model (IBM-2). With this method, we calculate the NMEs for all processes of interest in 0νβ−β− and 2νβ−β− and in 0νβ+β+, 0νECβ+, R0νECEC, 2νβ+β+, 2νECβ+, and 2νECEC. With this method, the Fermi matrix elements for 2νββ vanish, and those for 0νββ are considerably reduced. peerReviewed
$0\nu\beta\beta$ and $2\nu\beta\beta$ nuclear matrix elements in the interacting boson model with isospin restoration
We introduce a method for isospin restoration in the calculation of nuclear matrix elements (NME) for $0\nu\beta\beta$ and $2\nu\beta\beta$ decay within the framework of interacting boson model (IBM-2). With this method, we calculate NME for all processes of interest in $0\nu\beta^-\beta^-$, $2\nu\beta^-\beta^-$, and in $0\nu\beta^+\beta^+$, $0\nu\beta^+ EC^+$, $R0\nu ECEC$, $2\nu\beta^+\beta^+$, $2\nu\beta^+EC$, and $2\nu ECEC$. With this method, the Fermi (F) matrix elements for $2\nu\beta\beta$ vanish, and those for $0\nu\beta\beta$ are considerably reduced.