Coherent and incoherent ${\pi^0}$ photoproduction from the deuteron

Differential cross-sections for the reactions $d(\gamma,\pi^0)d$ and $d(\gamma,\pi^0)pn$ have been measured at MAMI with the TAPS detector setup in the energy range 140 MeV $< E_\gamma < 306$ MeV. By use of the Glasgow tagging spectrometer an 0.8 MeV energy resolution for photons incident on the target was achieved. The $\pi^0$ missing energy resolution was sufficient for a reliable separation of coherent and incoherent channels. The data for the break-up channel exhibit very strong final state interaction effects, whereas the observed angular dependence of the inclusive process $d(\gamma,\pi^0)X$ is in quantitative agreement with predictions for a quasi-free process. The observed absolute $d(\gamma,\pi^0)X$ cross-sections, on the other hand, are significantly smaller than predicted by the quasi-free process for $E_\gamma \gtrsim 250$ MeV. Associating this failure with the $\pi^0$ photoproduction on the neutron would suggest that its cross-section is up to 25% below the presently believed value