Abstract
We investigate the valence $u$ and $\bar{s}$ quark distribution functions of the $K^+$ meson, $v^{K(u)}(x,Q^2)$ and $v^{K(\bar{s})}(x,Q^2)$, in the framework of the chiral constituent quark model. We judiciously choose the bare distributions at the initial scale to generate the dressed distributions at the higher scale, considering the meson cloud effects and the QCD evolution, which agree with the phenomenologically satisfactory valence quark distribution of the pion and the experimental data of the ratio $v^{K(u)}(x,Q^2)/v^{\pi (u)}(x,Q^2)$. We show how the meson cloud effects affect the bare distribution functions in detail. We find that a smaller $SU(3)$ flavor symmetry breaking effect is observed, compared with results of the preceding studies based on other approaches.
Highlights
The SUð3Þ flavor symmetry has played an important role in the development of hadron physics since the first strange particle, the kaon, was discovered in 1947
Β and γ are the parameters to be determined, and NKðuÞ and NKðsÞ are the normalization factors. To determine those parameters we utilize the experimental data for the ratio of the valence quark distribution functions of the pion and kaon, vKðuÞðx; Q2Þ=vπðuÞðx; Q2Þ, at Q2 1⁄4 27 GeV2 [30]
We evaluate the dressing corrections to the bare u quark distribution function of the kaon with arbitrarily fixed parameters at the initial scale, and perform the quantum chromodynamics (QCD) evolution to obtain the dressed distribution at Q2 1⁄4 27 GeV2
Summary
The SUð3Þ flavor symmetry has played an important role in the development of hadron physics since the first strange particle, the kaon, was discovered in 1947. The calculated distribution functions are evolved by the Dokshitzer-Gribov-LipatovAltarelli-Parisi (DGLAP) equation to higher Q2 at which high energy scattering occurs in practice, and sea quarks and gluons emerge as PDFs. The existence of the meson cloud is based on the fact that the chiral symmetry of the QCD vacuum is spontaneously broken and the light pseudoscalar mesons are the corresponding NambuGoldstone bosons. We have found that their results can be reproduced within the chiral constituent quark model, and investigated the roles of the meson cloud effects in the pion valence quark distribution [29]. It is natural for us to extend our study to the kaon case to see the meson cloud effects and the SUð3Þ flavor symmetry breaking effect in the kaon quark distribution functions.
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