FLAVOR ASYMMETRY IN THE LIGHT-QUARK SEA OF THE NUCLEON

Parton distributions with an excess of down quarks over up quarks in t he sea can reproduce data on the structure functions F2(mu-p), F2(mu-n ), and xF3(v N). A model calculation in chiral field theory shows how an up-down asymmetry can arise from the dissociation of a quark into a quark plus a pion within the nucleon. This effect is large enough to account for the Gottfried-sum-rule defect reported by the New Muon Col laboration. Similar calculations may advance the understanding of othe r quasistatic properties of hadrons.