Measurements of the spin observables D_NN^′, P, and A_y in inelastic proton scattering from ¹²C and ¹⁶O at 198 MeV

Precise values of the normal-component spin observables D_NN^′, P, and A_y have been determined at an incident proton energy of 198 MeV for the T=0 (12.71 MeV) and T=1 (15.11 MeV) 1⁺ states in ¹²C for momentum transfers between 80 and 250 MeV/c, and for the T=0 (17.78 and 19.81 MeV) and T=1 (18.98 MeV) 4^- states in ¹⁶O for momentum transfers of 225–400 MeV/c. The data are compared with distorted wave impulse approximation calculations in which a microscopic treatment of the nuclear medium has been used to obtain an effective nucleon-nucleon interaction. Nuclear binding and Pauli blocking effects, as well as those due to the strong scalar and vector mean field potentials that arise in covariant treatments of nuclear matter, are incorporated using a G-matrix approach. Our results suggest that while the isovector channel of the effective nucleon-nucleon interaction is reasonably well understood, pronounced discrepancies between theory and experiment for the isoscalar transitions point towards problems with the relative strengths of the spin-orbit and tensor components. For the ¹²C states, these discrepancies are more difficult to interpret due to ambiguities in the nuclear structure.