Threshold photo/electro pion production - working group summary

Over the last few years, pion production off nucleons by real or virtual photons has become a central issue in the study of the non-perturbative structure of the nucleon, i.e. at low energies. Here, developments in detector and accelerator technology on the experimental side as well as better calculational tools on the theoretical one have allowed to gain more insight into detailed aspects of these processes and the physics behind them. One main trigger were the two papers by the Saclay and the Mainz groups, which seemed to indicate the violation of a so-called low energy theorem for the reaction γp → π0p. This lead to a flurry of further experimental and theoretical investigations. Another cornerstone was the rather precise electroproduction measurement γ*p → π0p at NIKHEF. Here, we wish to summarize the state of the art in calculating and measuring these processes in the threshold region. Furthermore, we outline what we believe have crystalized as the pertinent activities to be done in the near future. (orig.)