Proton-Neutron Pairing Amplitude as a Generator Coordinate for Double-Beta Decay

TL;DR

This paper introduces a novel method for calculating neutrinoless double-beta decay in 76Ge by incorporating proton-neutron pairing amplitudes as generator coordinates, enhancing the physical realism of the model.

Contribution

It develops a new approach that combines deformation and proton-neutron pairing as generator coordinates, allowing larger single-particle spaces and improved physics modeling in double-beta decay calculations.

Findings

The approach avoids instabilities near phase transitions.

Including proton-neutron pairing improves decay rate predictions.

The method surpasses traditional shell model limitations.

Abstract

We treat proton-neutron pairing amplitudes, in addition to the nuclear deformation, as generator coordinates in a calculation of the neutrinoless double-beta decay of 76Ge. We work in two oscillator shells, with a Hamiltonian that includes separable terms in the quadrupole, spin-isospin, and pairing (isovector and isoscalar) channels. Our approach allows larger single-particle spaces than the shell model and includes the important physics of the proton-neutron quasiparticle random-phase approximation (QRPA) without instabilities near phase transitions. After comparing the results of a simplified calculation that neglects deformation with those of the QRPA, we present a more realistic calculation with both deformation and proton-neutron pairing amplitudes as generator coordinates. The future should see proton-neutron coordinates used together with energy-density functionals.