Coherent π⁰ and η Photoproduction on the Deuteron

Coherent pion photoproduction, $d(\gamma,\pi^0)d$, is calculated in a coupled channels approach in momentum space using an elementary production operator that includes Born terms, vector meson exchange and $M1/E2$ $\Delta$-resonance excitation. The final state interaction is treated in the KMT multiple scattering approach that describes $\pi d$ elastic scattering well. Differential cross sections are found to agree well with existing ($\gamma, \pi^0$) data. The polarization observables $\Sigma , iT_{11}$ and the tensor analyzing powers are predicted for forthcoming experiments. A number of transparent relationships between polarization observables and the elementary production operator is derived. Finally, calculations are performed for coherent eta photoproduction, $d (\gamma, \eta)d$, in the threshold region which agree well with a very recent Mainz experiment.