Theoretical mean field and experimental occupation probabilities in the double beta decay system 76Ge to 76Se

TL;DR

This paper demonstrates that a self-consistent Hartree-Fock+BCS approach with experimental deformations significantly improves the modeling of occupation probabilities in the double-beta decay system 76Ge to 76Se, aligning well with recent experimental data.

Contribution

It introduces a self-consistent Hartree-Fock+BCS method with experimental deformations that better reproduces occupation probabilities and decay matrix elements in 76Ge to 76Se.

Findings

Improved agreement with experimental occupation probabilities.

Enhanced modeling of double-beta decay matrix elements.

Neutron spin-orbit strength larger than proton's yields best results.

Abstract

Usual Woods-Saxon single particle levels with BCS pairing are not able to reproduce the experimental occupation probabilities of the proton and neutron levels 1p_{3/2}, 1p_{1/2}, 0f_{5/2}, 0g_{9/2} in the double-beta decay system 76Ge to 76Se. Shifting down the 0g_{9/2} level by hand can explain the data but it is not satisfactory. Here it is shown that a selfconsistent Hartree-Fock+BCS approach with experimental deformations for 76Ge and 76Se may decisively improve the agreement with the recent data on occupation probabilities by Schiffer et al. and Kay et al. Best agreement with available data on 76Ge and 76Se, as well as on neighbor isotopes, is obtained when the spin-orbit strength for neutrons is allowed to be larger than that for protons. The two-neutrino double-beta decay matrix element is also shown to agree with data.