THE QUARK-ANTIQUARK ASYMMETRY OF THE NUCLEON SEA

Although the distributions of sea quarks and antiquarks generated by l eading-twist QCD evolution through gluon splitting g --> (q) over bar q are necessarily CP symmetric, the distributions of nonvalence quarks and antiquarks which are intrinsic to the nucleon's bound state wavef unction need not be identical. In this paper we investigate the sea qu ark-antiquark asymmetries in the nucleon wavefunction which are genera ted by a light-cone model of energetically-favored meson-baryon fluctu ations. The model predicts striking quark-antiquark asymmetries in the momentum and helicity distributions for the down and strange contribu tions to the proton structure function: the intrinsic d and s quarks i n the proton sea are predicted to be negatively polarized, whereas the intrinsic (d) over bar and (s) over bar antiquarks give zero contribu tions to the proton spin, Such a picture is supported by experimental phenomena related to the proton spin problem and the violation of the Ellis-Jaffe sum rule. The light-cone meson-baryon fluctuation model al so suggests a structured momentum distribution asymmetry for strange q uarks and antiquarks which could be relevant to an outstanding conflic t between two different determinations of the strange quark sea in the nucleon. The model predicts an excess of intrinsic d (d) over bar pai rs over u (u) over bar pairs, as supported by the Gottfried sum rule v iolation. We also predict that the intrinsic charm and anticharm helic ity and momentum distributions are not identical.