Meson cloud effects on the pion quark distribution function in the   chiral constituent quark model
  We investigate the valence quark distribution function of the pion $v^{\pi}(x,Q^2)$ in the framework of the chiral constituent quark model and evaluate the meson cloud effects on $v^{\pi}(x,Q^2)$. We explicitly demonstrate how the meson cloud effects affect $v^{\pi}(x,Q^2)$ in detail. We find that the meson cloud correction causes an overall 32\% reduction of the valence quark distribution and an enhancement at the small Bjorken $x$ regime. Besides, we also find that the dressing effect of the meson cloud will make the valence quark distribution to be softer in the large $x$ region. 
Akira Watanabe and Chung Wen Kao and Katsuhiko Suzuki
hep-ph nucl-th