Meson cloud effects on kaon quark distribution functions and the SU(3) flavor symmetry

We present our analysis on the valence quark distribution functions of the $K^{+}$ meson, $v^{K (u)} (x, Q^2)$ and $v^{K (\bar{s})} (x, Q^2)$, taking into account the meson cloud effects in the framework of the chiral constituent quark model. Assuming appropriate bare quark distribution functions at the initial scale, evaluating the Goldstone boson dressing corrections with the model, and performing the QCD evolution, one can obtain the realistic dressed distributions at a certain scale. The phenomenologically satisfactory valence quark distribution of the pion was obtained in the previous study and there are available experimental data of the valence $u$ quark distribution ratio $v^{K(u)} (x, Q^2) / v^{\pi (u)} (x, Q^2)$, which enable us to obtain the kaon quark distribution functions. Besides presenting the resulting dressed distributions, we also show how the meson cloud effects affect the bare distributions in detail. A striking result is that the observed size of the SU(3) flavor symmetry breaking is considerably smaller than those seen in the preceding works based on other approaches.