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Non-relativistic reduction of the S-matrix for the quasifree electron scattering process A ( e, e ′ p ) A − 1 is studied in order to understand the source of differences between non-relativistic and relativistic models. We perform an effective Pauli reduction on the relativistic expression for the S-matrix in the one-photon exchange approximation. The reduction is applied to the nucleon current only; the electrons are treated fully relativistically. An expansion of the amplitude results in a power series in the nuclear potentials. The series is found to converge rapidly only if the nuclear potentials are included in the nuclear current operator. The results can be cast in a form which reproduces the non-relativistic amplitudes in the limit that the potentials are removed from the nuclear current operator. Large differences can be found between calculations which do and do not include the nuclear potentials in the different orders of the nuclear current operator. In the high missing momentum region we find that the non-relativistic calculations with potentials included in the nuclear current up to second order give results which are close to those of the fully relativistic *

Single nucleon knockout reactions must be described in a consistent framework in order to extract information about nuclear structure and reaction mechanisms. Consistent relativistic models for the direct knockout contribution to the (e, e ′ p) and (γ, p) reactions have been developed and used previously to examine existing momentum distribution and cross section data for the two reactions 1 . We present results of calculations of spin observables obtained from these models of (e, e ′ p) and (γ, p) reactions. For the (e, e ′ p) reaction we consider the importance of the choice of kinematics and show that perpendicular kinematics result in distributions with relatively large cross sections and comparatively large polarizations. In the (γ, p) reactions the photon asymmetry and proton polarization are not very sensitive to changes in model ingredients when the incident photon energy is less than 100 M eV . For higher energies these observables show increasing sensitivity to modifications of both the bound and continuum wave functions.

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