Quenching of Gamow-Teller strengths and two-particle–two-hole configurations

International audienceWe apply the charge-exchange subtracted second random-phase approximation (SSRPA), based on Skyrme functionals, to investigate Gamow-Teller resonances in several closed-shell and closed-subshell nuclei, located in different regions of the nuclear chart. After having discussed the SSRPA findings obtained within different approximation schemes in Ca48, we compare our results with ab initio coupled-cluster predictions available for C and O isotopes, where two-body currents are included. Our integrated strengths, obtained by using one-body transition operators, are lower compared to the corresponding ab initio results. This indicates that, within our model, the inclusion of two-particle–two-hole configurations is indeed very effective and has an impact on the integrated strengths which is comparable to (and even stronger than) the one produced by the inclusion of two-body currents in ab initio results. By analyzing heavier nuclei, Zr90 and Sn132, we confirm the same conclusions that we have recently drawn for Ca48: the inclusion of two-particle–two-hole configurations is very effective in our model for providing strengths which are significantly more quenched than in other theoretical models and, thus, in better agreement with the experimental measurements. This occurs because two-particle–two-hole configurations have a density which strongly increases with the excitation energy. Their inclusion thus pushes a significant amount of the strength to higher energies, compared to what happens in other theoretical models, reducing in this way the cumulative sum of the strength up to excitation energies around 20–30 MeV