Threshold region photoproduction of neutral π mesons off complex nuclei

Photoproduction of π0 mesons off targets of 6Li, 12C, 28Si, 40Ca, natural Cd, and natural Pb was studied using a bremsstrahlung beam with endpoint energies of 140, 145, 150, and 155 MeV. Photoproduction from a liquid hydrogen target was employed as a normalization. The measured yields were found to be in disagreement with published theoretical cross sections for 6Li(ν,π0)6Li and also in disagreement with a simple schematic model which assumed only coherent contributions from the M1/sub +/ multipole. The schematic model, however, did approximately predict the relative magnitudes of the yield curves for the energy range 14--20 MeV over threshold