Polarized light-antiquark distributions in a meson-cloud model

Abstract

Flavor asymmetry is investigated in polarized light-antiquark distributions by a meson-cloud model. In particular, $\ensuremath{\rho}$ meson contributions to $\ensuremath{\Delta}\ifmmode \bar{u}\else \={u}\fi{}\ensuremath{-}\ensuremath{\Delta}\overline{d}$ are calculated. We point out that the ${g}_{2}$ part of $\ensuremath{\rho}$ contributes to the structure function ${g}_{1}$ of the proton in addition to the ordinary longitudinally polarized distributions in $\ensuremath{\rho}.$ This kind of contribution becomes important at medium $x(>0.2)$ with small ${Q}^{2}(\ensuremath{\sim}1{\mathrm{GeV}}^{2}).$ Including $\stackrel{\ensuremath{\rightarrow}}{N}\ensuremath{\rho}N$ and $\stackrel{\ensuremath{\rightarrow}}{N}\ensuremath{\rho}\ensuremath{\Delta}$ splitting processes, we obtain the polarized $\ensuremath{\rho}$ effects on the light-antiquark flavor asymmetry in the proton. The results show $\ensuremath{\Delta}\overline{d}$ excess over $\ensuremath{\Delta}\ifmmode \bar{u}\else \={u}\fi{},$ which is very different from some theoretical predictions. Our model could be tested by experiments in the near future.