Estimation of nuclear matrix elements of double- decay from shell model and quasiparticle random-phase approximation
Institute of Experimental and Applied Physics, Czech Technical University in Prague, Husova 240/5, 110 00, Prague 1, Czech Republic
2 Faculty of Chemistry, Materials and Bioengineering, Kansai University, Yamatemachi 3-3-35, 564-8680, Suita, Osaka, Japan
Accepted: 19 August 2021
Published online: 3 September 2021
The nuclear matrix element (NME) of neutrinoless double- () decay is an essential input for determining the neutrino effective mass, if the half-life of this decay is measured. Reliable calculation of this NME has been a long-standing problem because of the diversity of the predicted values of the NME, which depends on the calculation method. In this study, we focus on the shell model and the QRPA. The shell model has a rich amount of the many-particle many-hole correlations, and the quasiparticle random-phase approximation (QRPA) can obtain the convergence of the calculation results with respect to the extension of the single-particle space. It is difficult for the shell model to obtain the convergence of the NME with respect to the valence single-particle space. The many-body correlations of the QRPA may be insufficient, depending on the nuclei. We propose a new method to phenomenologically modify the results of the shell model and the QRPA compensating for the insufficiencies of each method using the information of other methods in a complementary manner. Extrapolations of the components of the NME of the shell model are made toward a very large valence single-particle space. We introduce a modification factor to the components of the NME of the QRPA. Our modification method yields similar values of the NME for the two methods with respect to Ca. The NME of the two-neutrino double- decay is also modified in a similar but simpler manner, and the consistency of the two methods is improved.
© The Author(s) 2021
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.