Isovector effective NN interaction in Si28(p→,n→)P28(6−) at 198 MeV

We report measurements of the cross section and a complete set of polarization observables for the Si28(p→,n→)P28(6−) reaction at a bombarding energy of 198 MeV. The data are compared with distorted wave impulse approximation calculations employing response functions normalized to inelastic electron scattering. The spin-longitudinal polarized cross section IDq is slightly over-predicted by the calculations, while the normal spin-transverse polarized cross section IDn is significantly under-predicted. The calculated in-plane spin-transverse IDp and spin-scalar ID0 polarized cross sections agree well with the experimental data. These results are consistent with those for Si28(p→,p→′)Si28(6−,T=1) scattering at the same energy, and thus it is concluded that isospin-mixing effects are not responsible for the discrepancy between theory and experiment in the (p→,p→′) case. Energy half-off-shell effects as medium effects on the effective nucleon-nucleon interaction are also investigated and found to be too small to be responsible for the discrepancy.