Coherent π0η photoproduction on s-shell nuclei

Coherent photoproduction of pi(0)eta on the deuteron and He-3 and He-4 nuclei is considered in the energy region from threshold to a laboratory photon energy E-gamma = 1.2 GeV. The transition amplitude is derived in the impulse approximation. The effects of pion absorption are included by means of the Fernbach-Serber-Taylor model. For the reactions on d and He-3 the interaction of the produced eta meson with the recoiling nucleus is taken into account. The corresponding eta d and eta He-3 scattering amplitudes are obtained as solutions of the few-body equations for eta NN and eta - 3N systems. The impact of this interaction on the differential cross section in the region of small relative.-nuclear momenta is discussed.