Polarized antiquark flavor asymmetry: Pauli blocking vs. the pion cloud
Abstract
The flavor asymmetry of the unpolarized antiquark distributions in the proton, dbar(x) - ubar(x) > 0, can qualitatively be explained either by Pauli blocking by the valence quarks, or as an effect of the pion cloud of the nucleon. In contrast, predictions for the polarized asymmetry Deltaubar(x) - Deltadbar(x) based on rho meson contributions disagree even in sign with the Pauli blocking picture. We show that in the meson cloud picture a large positive Deltaubar(x) - Deltadbar(x) is obtained from pi-N - sigma-N interference-type contributions, as suggested by chiral symmetry. This effect restores the equivalence of the 'quark' and 'meson' descriptions also in the polarized case.
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