5 research outputs found
Non-perturbative structure of the polarized nucleon sea
We investigate the flavour and quark-antiquark structure of the polarized
nucleon by calculating the parton distribution functions of the nucleon sea
using the meson cloud model. We find that the SU(2) flavor symmetry in the
light antiquark sea and quark-antiquark symmetry in the strange quark sea are
broken, {\it i.e.} \Delta\ubar < \Delta \dbar and \Delta s < \Delta \sbar.
The polarization of the strange sea is found to be positive, which is in
contradiction to previous analyses. We predict a much larger quark-antiquark
asymmetry in the polarized strange quark sea than that in the unpolarized
strange quark sea. Our results for both polarized light quark sea and polarized
strange quark sea are consistent with the recent HERMES data.Comment: RevTex, 17 pages plus 8 PS figure
On the phenomenological analyses of - asymmetry in the nucleon sea
Two phenomenological models which give opposite predictions for the
- asymmetry in the nucleon sea are re-analyzed carefully. It is
pointed out that although the quantitative results in both models depend
dramatically on the parameters, the predictions for the shape of in the two models are parameter independent and opposite. Thereby the
coming experiments are likely to be able to distinguish the two models. We find
that the reason for the two models giving opposite predictions is that the
fluctuation functions and parametrizations for the strange (anti-strange) quark
distribution in the baryon (meson) in the two models are quite different. To
further investigate these models, we use the same parametrizations for the
strange (anti-strange) distributions of the baryon (meson) in the two models.
We find that one of the models depends strongly on the parameter which controls
the behavior of the meson-baryon fluctuation function. Also the two models
agree on the shape and size of - for some values of the model
parameters, but can disagree strongly for others.Comment: RevTex, 11 pages, 7 Postscript figure
Moments of isovector quark distributions from lattice QCD
We present a complete analysis of the chiral extrapolation of lattice moments of all twist-2 isovector quark distributions, including corrections from Nπ and Δπ loops. Even though the Δ resonance formally gives rise to higher order non-analytic structure, the coefficients of the higher order terms for the helicity and transversity moments are large and cancel much of the curvature generated by the wave function renormalization. The net effect is that, whereas the unpolarized moments exhibit considerable curvature, the polarized moments show little deviation from linearity as the chiral limit is approached