Models for the polarized parton distributions of the nucleon

Abstract

Polarized deep inelastic scattering (DIS) data are analyzed in leading and next-to-leading order of QCD within the common ``standard'' scenario of polarized parton distributions with a flavor-symmetric light sea (antiquark) distribution $\ensuremath{\delta}\overline{q},$ and a completely ${\mathrm{SU}(3)}_{f}$ broken ``valence'' scenario with totally flavor-asymmetric light sea densities $(\ensuremath{\delta}\ifmmode \bar{u}\else \={u}\fi{}\ensuremath{\ne}\ensuremath{\delta}\overline{d}\ensuremath{\ne}\ensuremath{\delta}\overline{s}).$ The latter flavor-broken light sea distributions are modeled with the help of a Pauli-blocking ansatz at the low radiative or dynamical input scales of ${\ensuremath{\mu}}_{\mathrm{LO}(\mathrm{NLO})}^{2}=0.26 (0.40){\mathrm{GeV}}^{2}$ which complies with predictions of the chiral quark-soliton model and expectations based on the statistical parton model as well as with the corresponding, well established, flavor-broken unpolarized sea $(\overline{d}>\ifmmode \bar{u}\else \={u}\fi{}).$ Present semi-inclusive DIS data cannot yet uniquely discriminate between those two flavor-symmetric and flavor-broken polarized light sea scenarios.