  An NLO QCD analysis of the ZEUS data on $e^+ p$ deep inelastic scattering
together with fixed-target data has been performed from which the gluon and
quark densities of the proton and the value of the strong coupling parameter,
$\alpha_s(M_Z^2)$, have been extracted. The study includes a full treatment of
the experimental systematic uncertainties, including point-to-point
correlations. Different ways of incorporating correlated systematic
uncertainties into the fit are discussed and compared.

High Energy Physics - Phenomenology