Coherent and incoherent π~0 photoproduction from the deuteron

摘要

Differential cross-sections for the reactions d(γ, π~0)d and d(γ, π~0)pn have been measured at MAMI with the TAPS detector setup in the energy range 140 MeV < E_γ < 306 MeV. By use of the Glasgow tagging spectrometer an 0.8 MeV energy resolution for photons incident on the target was achieved. The π~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(γ, π~0)X is in quantitative agreement with predictions for a quasi-free process. The observed absolute d(γ, π~0)X cross-sections, on the other hand, are significantly smaller than predicted by the quasi-free process for E_γ approx.> 250 MeV. Associating this failure with the π~0 photoproduction on the neutron would suggest that its cross-section is up to 25% below the presently believed value.