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 $\delta \bar{q}$, and a completely SU(3)${}_f$ broken `valence' scenario with totally flavor-asymmetric light sea densities $(\delta \bar{u}\ne \delta \bar{d}\ne \delta \bar{s})$. The latter flavor-broken light sea distributions are modelled with the help of a Pauli-blocking ansatz at the low radiative/dynamical input scales of ${\mu }_{\mathrm{LO}(\mathrm{NLO})}^2=0.26$ (0.40) 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 ($\bar{d}>\bar{u}$). Present semi-inclusive DIS data cannot yet uniquely discriminate between those two flavor-symmetric and flavor-broken polarized light sea scenarios.

Comments: 39 pages, LaTeX