Eta-N Final State Interaction in incoherent Photoproduction of Eta-mesons from the Deuteron near Threshold

An analysis of incoherent photoproduction of $\eta$ mesons off the deuteron for photon energies from threshold to 800 MeV is presented. The dominant contribution, the $\gamma$N-$\eta$N amplitude, is described within an isobar model. Effects of the final state interactions in the $NN$ as well as the ${\eta}N$ systems are included employing models derived within the meson-exchange approach. It is found that their consideration is important. Specifically, due to an interference effect the influence of the $\eta N$ final state interaction is enhanced in the reaction $\gamma d \to np \eta$ close to threshold.