Chiral quark soliton model and flavor-asymmetricqq¯sea in the nucleon

By making full use of the advantage of the chiral quark soliton model, we investigate the flavor structure of the sea-quark components in the nucleon. First, through the analysis of the charge distributions of the proton and neutron, we demonstrate that the effect of sea quarks incorporated in this model can be identified with that of the cloud of pions surrounding the core of three valence quarks. Next, not only the integrated value but also the spatial structure of the $q\overline{q}$ scalar condensate in the nucleon is studied with emphasis upon the separate functions of the valence and sea quarks. The enhancement of the $\overline{d}d$ scalar condensate relative to the $\overline{u}u$ one in the proton is shown to be consistent with QCD phenomenology. We have also carried out a theoretical analysis of the Gottfried sum on the basis of the chiral quark soliton model and obtained a satisfactory agreement with the recent New Muon Collaboration measurement.