FLAVOR-ASYMMETRIC SEA QUARK DISTRIBUTION IN A CHIRAL POTENTIAL MODEL

Abstract

Flavor asymmetry of the sea quark distribution which expresses itself in the observed value of the Gottfried sum leads one to consider pion emission as directly contributing to the scale dependence of structure functions. As an example, we study the evolution of structure functions in a chiral potential model which incorporates the pion as the chiral-symmetry-restoring field and which was originally invented to explain the static properties of baryons. Evolution equations for the quark and pion densities are derived in the lowest order at subasymptotic Q2. The kernels of evolution for the effective quark densities turn out to be flavor-dependent and are endowed with properties quite distinct from those possessed by leading log QCD splitting functions. In particular, the commonly used probabilistic treatment of the evolution, which is legitimate in the kinematic region of the perturbative QCD evolution, is seen not to be valid in the domain of applicability of the chiral potential model. The model is shown to lead to nontrivial evolution of the nonsinglet moments in a manner consistent with the observed departure from the Gottfried sum rule in a low Q2 region. For higher Q2, the evolution of the Gottfried sum receives also an additive contribution not envisaged in the earlier works on the phenomenon.