Low energy scattering and photoproduction of η-mesons on deuterons

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Photo-production of η-mesons and their collisions with light nuclei are studied within the Alt-Grassberger-Sandhas (AGS) formalism for different parameters of ηN interaction. A three-body resonance or a quasi-bound state is found close to the ηd threshold. Expected manifestation of this resonant behavior of ηd elastic scattering in various processes involving ηd-system in their final states was found in calculations of the γd → ηd reaction in the framework of modified AGS equations. These calculations revealed peaks in the energy dependence of the total cross-section almost at the same energies as in the elastic ηd scattering. Meanwhile, such peaks did not appear in the impulse approximation (i.e. when ηd resonance was not taken into account). This sheds some light on the nature of the enhancement of η photo-production on deuteron observed recently in the low energy experiments.