Signature of the eta-NN configurations in coherent pi0 photoproduction on the deuteron

The photoproduction of a neutral pion on the deuteron is considered in the energy region around the eta threshold, where a bump-like structure was observed at very backward pion angles. Different dynamical aspects which may be responsible for this phenomenon are analysed within a theoretical frame which includes intermediate eta-NN configurations. The results show in particular, that a three-body treatment of the eta-NN interaction is of special importance.