Ingredients of nuclear matrix element for two-neutrino double-beta decay of 48Ca

TL;DR

This paper investigates the nuclear matrix element for two-neutrino double-beta decay of 48Ca using large-scale shell model calculations across one and two major shells, quantifying the impact of cross-shell excitations.

Contribution

It provides a quantitative evaluation of the effect of including two major shells in shell model calculations for double-beta decay.

Findings

Cross-shell excitations significantly affect the nuclear matrix element.

Comparison shows differences between single-shell and two-shell calculations.

Results improve understanding of nuclear structure effects in double-beta decay.

Abstract

Large-scale shell model calculations including two major shells are carried out, and the ingredients of nuclear matrix element for two-neutrino double beta decay are investigated. Based on the comparison between the shell model calculations accounting only for one major shell ($pf$-shell) and those for two major shells ($sdpf$-shell), the effect due to the excitation across the two major shells is quantitatively evaluated.