Photoproduction of jets at HERA in next-to-leading order QCD

Photoproduction of jets is one of the most important processes investigated at the electron-proton collider HERA. It not only allows to test the theory of strong interactions, quantum chromodynamics (QCD), but it also permits to measure the proton and photon structure functions with high precision. This requires exact theoretical predictions for the observed one- and two-jet cross sections. These cross sections are given here for the first time for direct and resolved photoproduction in next-to-leading order of perturbation theory. We present the complete analytical results for the Born terms, the virtual, and the real corrections. Here, we use the phase space slicing method to separate singular and regular regions of phase space by an invariant mass cut. In this way, all soft and collinear singularities can be either cancelled, or absorbed into the structure functions. Using a flexible Monte Carlo program, we evaluate the cross sections numerically and compare them to data from the experiments H1 and ZEUS. (orig.)