Analyzing powers for proton inelastic scattering to unnatural-parity states inCa40andSi28

Cross sections and analyzing powers in proton inelastic scattering leading to unnatural parity states of $2^{-}$, $T=0\mathrm{}$ (6.025 and 6.75 MeV), $2^{-}$, $T=1\mathrm{}$ (8.42 MeV) in ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ and $6^{-}$, $T=0\mathrm{}$ (11.58 MeV) and $6^{-}$, $T=1\mathrm{}$ (14.36 MeV) in ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ were measured at 65 MeV. These states are pair states of different isospin with the same spin and parity. The analyzing powers for a pair of $T=0\mathrm{}$ and $T=1\mathrm{}$ excitations in ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ show an isospin dependence not observed in ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$. The measured angular distributions were compared with microscopic distorted-wave Born approximation calculations using two versions of the effective nucleon-nucleon interaction. As expected, the interaction emphasizing the tensor contribution predicts analyzing powers and cross sections in better agreement with the experimental data. As factors to produce a difference in the analyzing powers between the $T=0\mathrm{}$ and the $T=1\mathrm{}$ states, the effect of two transferred orbital angular momentum amplitudes allowed in a transition and the energy dependence of the isoscalar spin-dependent terms in the effective interaction are discussed.