On the Effect of Binding in Deep Inelastic Scattering

The phenomenon of scaling in deep inelastic lepton-nucleon scattering is usually explained in terms of the Feynman parton model, and the logarithmic corrections to scaling are explained in the framework of perturbative QCD. For testing the validity of the parton model, we consider the deep inelastic electron scattering in a model in which the system electromagnetic current operator explicitly satisfies relativistic invariance and current conservation. Let the struck particle have the fraction ξ of the total momentum in the infinite momentum frame. Then it is shown that, due to binding of particles in the system under consideration, the Bjorken variable x no longer can be interpreted as ξ, even in the Bjorken limit and in zero order of the perturbation theory. We argue that, as a result, the data on deep inelastic scattering alone do not make it possible to determine the ξ distribution of quarks in the nucleon.