Electroweak Reactions in the Non-Perturbative Regime of QCD

These lectures are concerned with the structure of hadrons at low energies, where the strong coupling constant is large. Most of the hadronic world discussed here will be made up of the light u, d and s quarks since these are the constituents of the low-lying hadrons. The best way to gain information about the strongly interacting particles is thus the use of well-understood probes, such as the photon or the massive weak gauge bosons. At very low energies, the dynamics of the strong interactions is governed by constraints from chiral symmetry. This leads to the use of effective field theory methods which in the present context is called baryon chiral perturbation theory. In the first part of these lectures, I will briefly outline the basic framework of this effective field theory and use photo-nucleon processes to discuss the strengths and limitations of it. The basic degrees of freedom are the pseudoscalar Goldstone