Effects of orbital occupancies on the neutrinoless beta-beta matrix element of 76Ge

TL;DR

This study investigates how neutron and proton orbital occupancies influence the neutrinoless double beta decay matrix element of 76Ge, using a refined pnQRPA approach aligned with recent experimental data.

Contribution

It introduces a new pnQRPA calculation incorporating recent neutron occupancy measurements and realistic interactions, providing results closer to shell-model estimates.

Findings

The matrix element is smaller than previous pnQRPA calculations.

Results are closer to recent shell-model estimates.

Inclusion of experimental occupancy data improves model accuracy.

Abstract

In this work we use the recently measured neutron occupancies in the 76Ge and 76Se nuclei as a guideline to define the neutron quasiparticle states in the 1p0f0g shell. We define the proton quasiparticles by inspecting the odd-mass nuclei adjacent to 76Ge and 76Se. We insert the resulting quasiparticles in a proton-neutron quasiparticle random-phase approximation (pnQRPA) calculation of the nuclear matrix element of the neutrinoless double beta (0-nu-beta-beta) decay of 76Ge. A realistic model space and effective microscopic two-nucleon interactions are used. We include the nucleon-nucleon short-range correlations and other relevant corrections at the nucleon level. It is found that the resulting 0-nu-beta-beta matrix element is smaller than in the previous pnQRPA calculations, and closer to the recently reported shell-model results.