Elastic scattering of 200 MeV polarized protons fromC12,13and the optical potential

The differential cross sections and analyzing powers for 200 MeV protons elastically scattered from ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ have been measured in the angular region 6-115°. The ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ data were analyzed in terms of a local, complex, spindependent optical potential. The potentials were defined phenomenologically (simple or double Woods-Saxon forms) or derived from the impulse approximation in the Kerman-McManus-Thaler approach with and without a semiempirical correction for Pauli blocking. Acceptable fits to the data over the whole angular range were obtained only for a real central potential which exhibits a pronounced depression inside the nuclear surface, a feature also suggested by some theoretical models for medium-energy optical potentials.