Jet cross sections and extraction of alphas at HERA

                          ZEUS Collaboration

                              Abstract

Jet cross sections in deep inelastic ep scattering (DIS) 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 production 
in DIS and photoproduction and the trijet to dijet ratio in DIS
and compared with perturbative QCD predictions. A QCD analysis of the
measured observables was used to extract precise values of the
strong coupling and test its energy-scale dependence.