Analyzing powers for proton inelastic scattering to unnatural-parity states in Ca40 and Si28

Cross sections and analyzing powers in proton inelastic scattering leading to unnatural parity states of 2-, T=0 (6.025 and 6.75 MeV), 2-, T=1 (8.42 MeV) in Ca40 and 6-, T=0 (11.58 MeV) and 6-, T=1 (14.36 MeV) in Si28 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 and T=1 excitations in Ca40 show an isospin dependence not observed in Si28. 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 and the T=1 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. NUCLEAR REACTIONS Ca40(p→,p′)Ca40, Si28(p→,p′)Si28, Mg24(p→,p′)Mg24, E=65 MeV, unnatural parity states of Ex=6-15 MeV, measured σ(θ), analyzing power Ay(θ), resolution ∼35 keV, DWBA analysis.