Applications of Symmetry Breaking in Determining PDFs of the Nucleon

Studying the possible breaking of various parton model symmetries by the parton distribution functions of the nucleon can provide important information for the non-perturbative structure of hadrons and the strong interaction. We review theoretical calculations for the breaking of flavor symmetry, quark-antiquark symmetry and charge symmetry in the unpolarized and polarized nucleons using the meson cloud model. We report an estimation for the total distribution of strange and antistrange quarks in the nucleon by combining theoretical calculations of SU(3) flavor symmetry breaking with light antiquark distributions obtained from global analysis of available experimental data.Comment: 8 pages, 4 figures, LaTeX, talk presented at Pacific Spin 2011 (June 20-24, 2011, Cairns, Australia), to appear in the conference proceedings (AIP

The flavour asymmetry of polarized anti-quarks in the nucleon

We present a study of the flavour asymmetry of polarized anti-quarks in the nucleon using the meson cloud model. We include contributions both from the vector mesons and the interference terms of pseudoscalar and vector mesons. Employing the bag model, we first give the polarized valence quark distribution of the $\rho$ meson and the interference distributions. Our calculations show that the interference effect mildly increases the prediction for \Delta \dbar(x)-\Delta \ubar(x) at intermediate $x$ region. We also discuss the contribution of `Pauli blocking' to the asymmetry.Comment: 22 pages, LaTex, 5 PS figures. Version to appear in Eur. Phys. J. C. An appendix is added for expressions for the helicity dependent fluctuation functions. An error in the programme for fluctuation function f_{(\pi\rho)\Delta /N} is corrected, which increases numerical results by about 10%. Unchanged conclusion