Studies of hard scattering in photoproduction at the ep storage ring HERA with the H1 detector

This thesis presents the analysis of hard interaction processes in quasi-real photo-production. The data have been recorded with the H1-detector at electron-proton collider HERA in 1993. The analysis used an integrated luminosity of about 290 nb-1. The results correspond to a kinematical range Q2<0.01 GeV2, 0.25<y<0.7 and 150<√sγp<250 GeV. The inclusive jet differential cross-section has been measured as a function of jet transverse energy, ETjet, and pseudorapidity, ηjet. Leading order QCD Monte-Carlo calculations, which include both resolved and direct photon processes, initial and final state leading logarithm parton showers, and additional interactions of spectator partons in the resolved photon-proton collisions, describe in general the shape and magnitude of the measured ηjet and ETjet distributions. Events with no hadronic energy flow in a large interval of pseudorapidity in the proton direction have been observed in photon-proton interactions. These events are interpreted as photon diffractive dissociation. In these events features which can be attributed to hard parton scattering have been found, namely production of high pT particles and jets. Results are compared with Monte-Carlo calculations which assume hard scattering between partons in the photon and in the Pomeron. (orig.)