Final state interactions and relativistic effects in the (e→,e’p) reaction

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Abstract
The five response functions which characterize the (e→,e’p) reaction are calculated in the distorted wave impulse approximation using a Dirac equation formulation of the nuclear bound and scattering wave functions and the usual free Dirac current operator. By evaluating the current matrix elements in momentum space, it is possible to recover the traditional Schrödinger dynamics and thus to study off-shell effects from the proton-nucleus final state interaction in both the relativistic and the nonrelativistic approaches. The longitudinal response function with relativistic effects included is reduced by about 20 percent relative to the nonrelativistic results. This is shown to be due to the Dirac final state interaction. Relativistic nuclear bound-state effects are found to be small in this reaction. The other four response functions show relativistic effects on the order of 5 to 10 percent. Off-shell effects are shown to be especially important in the interference response functions. A rough measure of the violation of current conservation in such calculations is presented and its implications for the calculations are discussed.