Nuclear structure studies of double Gamow-Teller strength

TL;DR

This paper investigates double Gamow-Teller strength distributions in Calcium isotopes using the nuclear shell model, analyzing sum rule fulfillment and the effects of level degeneracies on the results.

Contribution

It introduces a detailed shell model calculation of double Gamow-Teller strength, including the role of intermediate states and sum rule verification.

Findings

Sum rules are approximately fulfilled in full calculations.

Degeneracy restoration improves agreement with sum rules.

Number of intermediate states contributing is explicitly determined.

Abstract

The double Gamow-Teller strength distributions in even-$A$ Calcium isotopes were calculated using the nuclear shell model by applying the single Gamow-Teller operator two times sequentially on the ground state of the parent nucleus. The number of intermediate states actually contributing to the results was determined. The sum rules for the double Gamow-Teller operator in the full calculation were approximately fulfilled. In the case that the symmetry is restored approximately by introducing degeneracies of the $f$-levels, and the $p$-levels in the $fp$-model space, the agreement with the sum rules was very close.