High-Energy Nonlocal Nucleon-Nucleus Optical Potential for a Central Two-Body Force with Second-Order Corrections to the Impulse Approximation

A calculation of the high-energy nucleon-nucleus optical potential is carried out for a central two-body force in the energy region 90-310 MeV. We first show that arbitrarily assuming a reduced mass of $0.44m$ for the two-body collision in the nucleus improves the fit to experiment. We then present a novel method for correcting the impulse approximation for terms of second order in the two-body force. Application of this method indicates that the impulse approximation is reliable at 310 MeV. Considerable corrections are found below this energy which substantially decrease the discrepancy between theory and experiment. Off-energy-shell nonlocal effects are of third order in the three-body force and cannot be included with complete consistency. However, there are indications that they might be small. Pair-correlation effects are ignored throughout this work.