Jet cross sections in DIS and photoproduction at HERA

                          ZEUS Collaboration

                              Abstract

Jet cross sections in deep inelastic ep scattering and
photoproduction were measured with the ZEUS detector at HERA using
an integrated luminosity of up to 500 pb^-1. Measurements of
differential cross sections are presented for inclusive-jet and dijet
production and compared with perturbative QCD predictions. Regions of
phase space where the cross sections are sensitive to the gluon
content of the proton with small uncertainties were identified. These
measurements have the potential to constrain the gluon density in the
proton when included as input to global QCD fits. A QCD analysis of the
measured cross sections was also used to extract precise values of the
strong coupling and test its energy-scale dependence.