Backward pion photoproduction

We present a systematic analysis of backward pion photoproduction for the reactions γp→π0p and γp→π+n. Regge phenomenology is applied at invariant collision energies above 3GeV in order to fix the reaction amplitude. A comparision with older data on π0- and π+-photoproduction at θ=180 indicates that the high-energy limit as given by the Regge calculation could be reached possibly at energies of around √(s)≅3 GeV. In the energy region of √(s)≤2.5 GeV, covered by the new measurements of γp→π0 p differential cross-sections at large angles at ELSA, JLab, and LEPS, we see no clear signal for a convergence towards the Regge results. The baryon trajectories obtained in our analysis are in good agreement with those given by the spectrum of excited baryons. (orig.)