Meson cloud and SU(3) symmetry breaking in parton distributions

We apply the meson cloud model to the calculation of non-singlet parton dis tributions in the nucleon sea, including the octet and the decuplet cloud b aryon contributions. We give special attention to the differences between n on-strange and strange sea quarks, trying to identify possible sources of S U(3) flavor breaking. An analysis in terms of the kappa parameter is presen ted, and we find that the existing SU(3) flavor asymmetry in the nucleon se a can be quantitatively explained by the meson cloud. We also consider the Sigma (+) baryon, finding similar conclusions.