Hardonic Final States of Deep-Inelastic Processes in Simple Quark-Parton Models

Bjorken and Feynman have suggested a quark-parton-model approach to predicting the final-state hadron spectra in deep-inelastic processes. Since the final-state interaction in their approach is characterized by short-range correlations in rapidity, it is natural to ask whether parton models with final-state interactions based on conventional multiperipheral dynamics might provide realizations of their picture. This is found to be untrue. We argue by studying perturbation-theory models (${\phi }^3$ and cutoff vector-gluon ladder models) and by formulating a rather general intuitive space-time argument that in naive parton models of this type one cannot avoid the appearance of isolated-quark quantum numbers in the final state. In the $\lambda {\phi }^3$ models the final-state interaction always vanishes in the deep-inelastic region (as well as in the high-energy annihilation region) regardless of the size of $\lambda$. In the vector-gluon model, the final-state interaction does not vanish asymptotically, but the struck quark parton cannot exchange its charge with the target fragments. The character of parton dynamics necessary to realize the Bjorken-Feynman picture is discussed.