Nonperturbative structure of the polarized nucleon sea

We investigate the flavor 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, i.e., Δu-bar<Δd-bar and Δs<Δs-bar. The polarization of the strange sea is found to be positive, which is in contradiction with 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 the polarized light quark sea and the polarized strange quark sea are consistent with the recent HERMES data