Exclusive Photon-Induced Hadronic Reactions at Large Momentum Transfers

It is generally assumed that due to factorization of long- and short-distance dynamics perturbative QCD can be applied to exclusive hadronic reactions at large momentum transfers. Within such a perturbative approach diquarks turn out to be a useful phenomenological device to model non-perturbative effects still observable in the kinematic range accessible by present-days experiments. The basic ingredients of the perturbative formalism with diquarks, i.e. Feynman rules for diquarks and quark-diquark wave functions of baryons, are briefly summarized. Applications of the diquark model to the electromagnetic form factors of the proton in the space- as well as time-like region, Compton-scattering off protons, gamma-gamma -> p-pbar, and photoproduction of Kaons are discussed.