Determination of flavor asymmetry for Σ±\Sigma^{\pm} by the Drell-Yan process

Flavor asymmetries for the valence and sea quarks of the $\Sigma^{\pm}$ can be obtained from Drell-Yan experiments using charged hyperon beams on proton and deuteron targets. A large, measurable difference in sea quark asymmetries is predicted between SU(3) and pseudoscalar meson models. The latter predict that in $\Sigma^{+}$, $\bar{u}/\bar{d} \leq 1/2$, whereas the former predict $\bar{u}/\bar{d} \approx 4/3$. Estimates of valence quark asymmetries based on quark models also show large deviations from SU(3) predictions, which should be measurable.Comment: 15 pages, latex. Figures available from [email protected]. To be published in Phys. Lett.

Omega Meson Cloud and the Proton's Light Anti-Quark Distribution

We use the meson cloud model of the nucleon to calculate distribution functions for $(\bar {d} - \bar{u})$ and $\bar{d}/\bar{u}$ in the proton. Including the effect of the omega meson cloud, with a coupling constant $g_\omega^2/4\pi\approx 8$, allows a reasonably good description of the data.Comment: 6 pages, 2 figures, LaTe

The Quark Distributions in the \Sigma^+ Hyperon

We use the meson cloud model and the Sullivan mechanism to estimate the sea flavor asymmetry in the \Sigma^+ baryon and calculate the distribution functions of both sea and valence quarks. We find large deviations from SU(3).Comment: 13 pages, 11 figure

Taming the Pion Cloud of the Nucleon

We present a light-front determination of the pionic contribution to the nucleon self-energy, $\Sigma_\pi$, to second-order in pion-baryon coupling constants that allows the pion-nucleon vertex function to be treated in a model-independent manner constrained by experiment. The pion mass $\mu$ dependence of $\Sigma_\pi$ is consistent with chiral perturbation theory results for small values of $\mu$ and is also linearly dependent on $\mu$ for larger values, in accord with the results of lattice QCD calculations. The derivative of $\Sigma_\pi$ with respect to $\mu^2$ yields the dominant contribution to the pion content, which is consistent with the $\bar{d}-\bar{u}$ difference observed experimentally in the violation of the Gottfried sum rule.Comment: 11 pages, 3 figure

Light quark distributions in the proton sea

We use the meson cloud model to calculate $\bar{d}(x) - \bar{u}(x)$ and $\bar{d}(x)/\bar{u}(x)$ in the proton. We show that a modification of the symmetric, perturbative part of the light quark sea provides better agreement with the ratio $ \bar{d}(x)/\bar{u}(x).Comment: 4 pages, 2 figures, LaTeX. Talk presented at PANIC 9