Threshold π0 photoproduction on 3He

The cross section for π0 photoproduction on 3He has been calculated for energies 0-20 MeV above the production threshold. The calculations have been performed in a nuclear K-matrix formalism to account for the effect of the π+-π0 mass difference which gives a 20% decrease of the cross section close to threshold. Within the static approximation, we find that the effective range expansion is valid for the first 20 MeV above threshold, permitting a simple parametrisation of the nuclear electric dipole amplitude in this energy range. (author)