Radiative Parton Model Analysis of Polarized Deep Inelastic Lepton Nucleon Scattering

A leading order QCD analysis of spin asymmetries in polarized deep inelastic lepton nucleon scattering is presented within the framework of the radiative parton model. Two resulting sets of plausible leading order spin dependent parton distributions are presented, respecting the fundamental positivity constraints down to the low resolution scale $Q^2=\mu_{LO}^2=0.23$ GeV$^2$. The $Q^2$ dependence of the spin asymmetries $A_1^{p,n,d}(x,Q^2)$ is investigated in the range $1 \leq Q^2 \leq 20$ GeV$^2$ and shown to be non-negligible for $x$-values relevant for the analysis of present data and possibly forthcoming data at HERA.