On the Investigation of the Proton Structure Using QED Compton Events in ep Scattering

QED Compton scattering at HERA is discussed in terms of the information it may reveal on the proton structure at low momentum transfers Q. Detailed Monte Carlo studies are performed which show that the analysis of inelastic QED Compton events allows the extension of present HERA structure function measurements to a kinematic regime, which up to now was only accessed in fixed target data. For these studies an improved version of the COMPTON event generator is used, where special emphasis has been put on modelling the hadronic final state at low invariant masses. As the low Q regime is sometimes also discussed in the context of the collinear approximation and the possibility of measuring the photonic content of the proton, the Monte Carlo studies are also used to check the validity of this approach. It is found that the proposed concept of a photon density γ of the proton does not provide sufficient accuracy for the description of inelastic QED Compton scattering.