Influence of intermediate ηNN interaction on spin asymmetries for γd→π0d reaction near the η-threshold within a three-body approach

The influence of intermediate ηNN interaction on spin asymmetries for coherent π0-photoproduction on the deuteron in the energy region around the η-threshold is studied using a three-body model with separable two-body interactions. We calculate all possible spin asymmetries with polarized photons and/or oriented deuterons and compare our results with available data. The calculations are based on a theoretical approach which includes the amplitudes of the impulse approximation, two-body process with πN- and ηN-rescattering, and the higher order terms in the multiple scattering series for the intermediate ηNN interaction. We found that the results for spin asymmetries of the differential cross section differ significantly from those calculated by a simple model in which only the impulse approximation and first-order rescattering contributions are considered. The effect of intermediate ηNN interaction is significant in certain spin asymmetries, specially at extreme backward pion angles. It turns out that the inclusion of a full ηNN three-body contribution is quite essential. The spin asymmetries of the total cross section are much less affected by rescattering contributions. Compared to the experimental data from YerPhi Collaboration for the linear photon asymmetry, sizeable discrepancies are found.