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 Si 28 ( p → , n → ) P 28 ( 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 I D q is slightly over-predicted by the calculations, while the normal spin-transverse polarized cross section I D n is significantly under-predicted. The calculated in-plane spin-transverse I D p and spin-scalar I D 0 polarized cross sections agree well with the experimental data. These results are consistent with those for Si 28 ( p → , p → ′ ) Si 28 ( 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.