Polarized antiquark flavor asymmetry Δ(u)over-bar(x)-Δ(d)over-bar(x) and the pion cloud

The flavor asymmetry of the unpolarized antiquark distributions in the proton, (v) over bar (x) - (d) over bar (x) < 0, can qualitatively be explained as an effect of the pion cloud. Corresponding predictions have been made for the polarized asymmetry, Delta(u) over bar (x) - Delta(d) over bar (x), based on rho-meson contributions. These estimates differ in sign and magnitude from those obtained in quark-based models, which give Delta(u) over bar (x) - Delta(d) over bar (x) > 0. Using a simple chiral linear sigma model as an example, we demonstrate that in the meson cloud picture a large positive Delta(u) over bar (x) - Delta(d) over bar (x) can be obtained from pi-sigma interference contributions. This calls into question previous estimates based on rho-meson contributions alone, and indicates how the results of the meson cloud picture may be reconciled with those of quark-based models.