arXiv subjects
Publications and source records attributed to Ernest M. Henley.
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).
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 $g_ω^2/4π\approx 8$, allows a reasonably good description of the data.
The electric dipole moments of nucleons (NEDM, d_N) are calculated using the method of QCD sum rules. Our calculations are based on the parity and time reversal violating parameter $\thetabar$ in QCD and establish a functional dependence of the NEDM on $\thetabar$, without assuming a perturbative expansion of this symmetry breaking parameter. The results obtained from the QCD sum rules approach are shown to be consistent with the general symmetry constraints on CP violations in QCD, including the necessity of: (1) finite quark masses, (2) spontaneous chiral symmetry breaking, and (3) the U_A(1) anomaly. Given the current experimental upper bound on the neutron electric dipole moment (nEDM), d_n < 10^(-25) e-cm, we find | \thetabar | < 10^(-9). This result is compatible with previous calculations of nEDM using different techniques and excludes the possibility of solving the strong CP problem within QCD via a dynamical suppression mechanism.
We use the meson cloud model and the Sullivan mechanism to estimate the sea flavor asymmetry in the Σ^+ baryon and calculate the distribution functions of both sea and valence quarks. We find large deviations from SU(3).
Examples are given of the usefulness of electrons in interaction with nuclei for probing fundamental interactions and structure
Flavor asymmetries for the valence and sea quarks of the $Σ^{\pm}$ 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 $Σ^{+}$, $\bar{u}/\bar{d} \leq 1/2$, 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.
We propose a flavor asymmetry in the light quark sea of $Σ^{\pm}$, which can be measured in Drell-Yan experiments using charged hyperon beams on proton and deuteron targets. Such a measurement would help to reinforce the presence of pseudoscalar mesons in a quark model of baryons.
Some recent experimental and theoretical work on 1) charge symmetry-breaking, 2) parity non-conservation, and 3) searches for breaking of time reversal invariance are reviewed. The examples illustrate the uses of symmetry to learn about underlying dynamics and/or structure.