Estimation of 2p2h effect on Gamow-Teller transition with Second Tamm-Dancoff-Approximation

Two-particle two-hole (2p2h) effect on the Gamow-Teller (GT) transition for neutron-rich nuclei is studied by the second Tamm-Dancoff approximation (STDA) with the Skyrme interaction. Unstable $^{24}$O and $^{34}$Si, and stable $^{48}$Ca nuclei are chosen to study the quenching and fragmentation of the GT strengths. Correlation of the 2p2h configurations causes $20$\% quenching and downward shift of GT giant resonances (GTGRs). The residual interaction changing relative angular momentum, appeared in the tensor force part, gives a meaningful effect to the GT strength distributions. In this work, $17$ to $26$ \% of the total GT strengths are brought to high energy region above GTGRs. In particular, the tensor force brings strengths to high energy more than $50$ MeV. STDA calculation within a small model space for 2p2h configuration is also performed and experimental data of $^{48}$Ca is reproduced reasonably.

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