Spin-rotation parameterQfor 800 MeV proton elastic scattering fromO16,Ca40, andPb208

The spin-rotation parameter Q(theta) was measured for 800 MeV p→${+}^{16}$O, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$, and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ elastic scattering for 2°≤${\mathrm{theta}}_{\mathrm{lab}\mathrm{\le }21\mathrm{°}}$. Microscopic ‘‘relativistic’’ (Dirac equation dynamics) and ‘‘nonrelativistic’’ (Schrödinger equation dynamics) optical model predictions are compared with the data. Slight preference for the relativistic impulse approximation approach is observed, but a marked mass dependence of the quality of the fit is evident. Other calculations are presented which suggest that inclusion of nuclear two-body correlation effects in the relativistic impulse approximation model might lead to better agreement with experiment.