Role of meson degrees of freedom in deep-inelastic lepton-nucleon scattering

Abstract

Some aspects of the meson cloud around the nucleon for deep-inelastic lepton scattering are studied in the framework of the Sullivan formalism. We present a simple two-phase model of the nucléon. Renormalization of the valence-quark distribution due to the mesonic cloud is taken into account explicitly. We study the dependence of different quantities on the cut-off parameter of the form factor, the role of different mesons in deep-inelastic scattering, and SU(2) F symmetry breaking in the nucleon sea in connection to the Gottfried sum rule. It is possible to obtain agreement with the CCFR data using hard-meson NN form factors, which are almost consistent with the Bonn meson-exchange model. For full consistency the model requires a readjustment of quark distributions in the bare baryon to account for the dressing with the mesonic cloud. The E615 data on 1 2 (ū + d̄) − s̄ restrict the cut-off parameter in the dipole form factor to about 1.2 GeV. For this value of the cut-off parameter we get the largest violation of the Gottfried sum rule, about half of that observed by NMC.