Polarized antiquark flavor asymmetry Δanti u(x)-Δanti d(x) and the pion cloud

The flavor asymmetry of the unpolarized antiquark distributions in the proton, anti u(x)- anti d(x)<0, can qualitatively be explained as an effect of the pion cloud. Corresponding predictions have been made for the polarized asymmetry, Δanti u(x)-Δ anti d(x), based on rho-meson contributions. These estimates differ in sign and magnitude from those obtained in quark-based models, which give Δanti u(x)-Δanti d(x)>0. Using a simple chiral linear sigma model as an example, we demonstrate that in the meson cloud picture a large positive Δanti u(x)-Δanti d(x) can be obtained from π-σ 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. (orig.)