Off-shell electron-nucleon cross sections: The impulse approximation

Abstract

With the goal of improving the analysis of quasi-elastic (e, e′) and (e, e′N) experiments, ambiguities in the impulse approximation are investigated by comparing various off-shell extrapolations of the Rosenbluth cross section. It is found that these ambiguities are especially large for low incident electron energies and momentum transfers and that they can be reduced by applying various physical constraints, such as those due to Lorentz invariance and current conservation. In particular the latter is important: most off-shell cross sections that have been used do not treat this correctly and, as a consequence, in the limit of the photon point give infinite photoabsorption cross sections.