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

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

New approach to 4^4He charge distribution

We present a study of the $^4$He charge distribution based on realistic nucleonic wave functions and incorporation of the nucleon's quark substructure. The central depression of the proton point density seen in modern four-body calculations is too small by itself to lead to a correct description of the charge distribution. We utilize six-quark structures calculated in the Chromodielectric Model for N-N interactions, and we find a swelling of the proton charge distribution as the internucleon distance decreases. These charge distributions are combined with the $^4$He wave function using the Independent Pair Approximation and two-body distributions generated from Green's Function Monte Carlo calculations. We obtain a reasonably good fit to the experimental charge distribution without including meson exchange currents.Comment: 9 pages, LaTeX, 4 figures (Figures 1 and 2 doesn't exist as postscript files : they are only available on request

Renormalization of the singular attractive 1/r41/r^4 potential

We study the radial Schr\"odinger equation for a particle of mass $m$ in the field of a singular attractive $g^2/{r^4}$ potential with particular emphasis on the bound states problem. Using the regularization method of Beane \textit{et al.}, we solve analytically the corresponding ``renormalization group flow" equation. We find in agreement with previous studies that its solution exhibits a limit cycle behavior and has infinitely many branches. We show that a continuous choice for the solution corresponds to a given fixed number of bound states and to low energy phase shifts that vary continuously with energy. We study in detail the connection between this regularization method and a conventional method modifying the short range part of the potential with an infinitely repulsive hard core. We show that both methods yield bound states results in close agreement even though the regularization method of Beane \textit{et al.} does not include explicitly any new scale in the problem. We further illustrate the use of the regularization method in the computation of electron bound states in the field of neutral polarizable molecules without dipole moment. We find the binding energy of s-wave polarization bound electrons in the field of C$_{60}$ molecules to be 17 meV for a scattering length corresponding to a hard core radius of the size of the molecule radius ($\sim 3.37$ \AA). This result can be further compared with recent two-parameter fits using the Lennard-Jones potential yielding binding energies ranging from 3 to 25 meV.Comment: 8 page