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Coherent one-particle one-hole (1p1h) excitations have given us effective insights into general nuclear excitations. However, the two-particle two-hole (2p2h) excitation beyond 1p1h is now recognized as critical for the proper description of experimental data of various nuclear responses. The spin-flip charge-exchange reactions $^{48}{rm Ca}(p,n)^{48}{rm Sc}$ are investigated to clarify the role of the 2p2h effect on their cross sections. The Fermi transition of $^{48}{rm Ca}$ via the $(p,n)$ reaction is also investigated in order to demonstrate our framework. The transition density is calculated microscopically with the second Tamm-Dancoff approximation, and the distorted-wave Born approximation is employed to describe the reaction process. A phenomenological one-range Gaussian interaction is used to prepare the form factor. For the Fermi transition, our approach describes the experimental behavior of the cross section better than the Lane model, which is the conventional method. For spin-flip excitations including the GT transition, the 2p2h effect decreases the magnitude of the cross section and does not change the shape of the angular distribution. The $Delta l=2$ transition of the present reaction is found to play a negligible role. The 2p2h effect will not change the angular-distributed cross section of spin-flip responses. This is because the transition density of the Gamow-Teller response, the leading contribution to the cross section, is not significantly varied by the 2p2h effect.
Spin-isospin transitions in nuclei away from the valley of stability are essential for the description of astrophysically relevant weak interaction processes. While they remain mainly beyond the reach of experiment, theoretical modeling provides impo
The theoretical approach to a sequential heavy ion double charge exchange reaction is presented. A brief introduction into the formal theory of second-order nuclear reactions and their application to Double Single Charge Exchange (DSCE) reactions by
Proton-${}^3$H elastic scattering and charge-exchange reaction ${}^3$H$(p,n){}^3$He in the energy regime above four-nucleon breakup threshold are described in the momentum-space transition operator framework. Fully converged results are obtained usin
Small-angle, two-particle correlation functions have been measured for 36Ar+ 112,124Sn collisions at E/A = 61 MeV. Total momentum gated neutron-proton (np) and proton-proton (pp) correlations are stronger for the 124Sn-target. Some of the correlation
The strong interactions among nucleons have an approximate spin-isospin exchange symmetry that arises from the properties of quantum chromodynamics in the limit of many colors, $N_c$. However this large-$N_c$ symmetry is well hidden and reveals itsel