Reaction γd→π0dand the small components of the deuteron wave function

We calculate the differential cross section and the photon asymmetry of the reaction γd→${\mathrm{\pi }}^0$d for incident photon energies below 1 GeV and compare with data at θ=130°. Our formalism, based on the spectator-on-mass-shell approximation, is fully relativistic and uses the dNN vertex of Buck and Gross and a recently developed model for the elementary γN→πN amplitude that describes well the first and second resonance regions. We find large sensitivity to the small components of the deuteron wave function in the energy region of the Roper resonance. Comparison to experimental data points towards a deuteron wave function with a high probability of small components.