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arXiv · 2007.04957

Gamow-Teller strength in $^{48}$Ca and $^{78}$Ni with the charge-exchange subtracted second random-phase approximation

D. Gambacurta·M. Grasso·J. Engel
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Abstract

We develop a fully self-consistent subtracted second random-phase approximation for charge-exchange processes with Skyrme energy-density functionals. As a first application, we study Gamow-Teller excitations in the doubly-magic nucleus $^{48}$Ca, the lightest double-$\beta$ emitter that could be used in an experiment, and in $^{78}$Ni, the single-beta-decay rate of which is known. The amount of Gamow-Teller strength below 20 or 30 MeV is considerably smaller than in other energy-density-functional calculations and agrees better with experiment in $^{48}$Ca, as does the beta-decay rate in $^{78}$Ni. These important results, obtained without \textit{ad hoc} quenching factors, are due to the presence of two-particle -- two-hole configurations. Their density progressively increases with excitation energy, leading to a long high-energy tail in the spectrum, a fact that may have implications for the computation of nuclear matrix elements for neutrinoless double-$\beta$ decay in the same framework.

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D. Gambacurta, M. Grasso, J. Engel. 2020-07-09. Gamow-Teller strength in $^{48}$Ca and $^{78}$Ni with the charge-exchange subtracted second random-phase approximation. https://doi.org/10.1103/physrevlett.125.212501

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