$0\nu\beta\beta$ and $2\nu\beta\beta$ nuclear matrix elements in the interacting boson model with isospin restoration

TL;DR

This paper presents a new method for restoring isospin symmetry in nuclear matrix element calculations within the interacting boson model, significantly reducing Fermi matrix elements for double beta decay processes.

Contribution

The authors introduce an isospin restoration technique in IBM-2, enabling more accurate NME calculations for various double beta decay modes, with notable reductions in Fermi matrix elements.

Findings

Fermi matrix elements for 2νββ vanish with the new method.

Fermi matrix elements for 0νββ are significantly reduced.

The method applies to multiple decay modes, improving NME accuracy.

Abstract

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.