QCD analyses of HERA cross section data

Abstract

The H1 and ZEUS Collaborations have performed new next-to-leading order QCD analyses to determine the parton density functions of the proton. QCD fits are performed using inclusive neutral and charged deep inelastic scattering cross sections from HERA-I. The fits include a full treatment of experimental systematic uncertainties, taking into account point-to-point correlations. The extracted parton densities are in agreement with those from global fits. Since HERA inclusive data provide no direct information on the high-x gluon, an independent fit has been performed by the ZEUS Collaboration in which the inclusive cross sections are supplemented by jet data from neutral current deep inelastic scattering and photoproduction. The determination of the gluon distribution is significantly improved in such fits, allowing a competitive extraction of the strong coupling, alpha_s(MZ).