Large angle elastic differential cross section and analyzing power data are reported for 497.5 MeV p→${+}^{40}$Ca. The characteristic diffraction pattern extends to the largest momentum transfer, 5.3 ${\mathrm{fm}}^{\mathrm{-}1}$. Theoretical models which incorporate either relativistic or nonrelativistic dynamics do not quantitatively describe the data for q>3.5 ${\mathrm{fm}}^{\mathrm{-}1}$. Possible explanations for the discrepancy are suggested.

• Received 5 October 1987

DOI:https://doi.org/10.1103/PhysRevC.37.1307