Dirac impulse approximation predictions for cross sections and spin observables in elastic proton scattering by ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ at energies of 200, 500, and 800 MeV are presented. The analysis is based on complete sets of Lorentz-invariant NN amplitudes determined from a meson-exchange model of the nuclear force. Effects of relativistic nuclear densities are explored including estimates of the vacuum polarization corrections based on quantum hadrodynamics. Effects of Pauli blocking are considered using the approximations of Murdock and Horowitz. A good description of the experimental data is obtained over a broad energy range and over a wide variation of nuclear size based on the generalized impulse approximation. Vacuum polarization corrections are found to enhance the agreement between theory and experiment.

• Received 11 December 1987

DOI:https://doi.org/10.1103/PhysRevC.38.2289