THE ELECTRIC-DIPOLE AMPLITUDES OF THE NEUTRAL PION-PHOTOPRODUCTION ONTHE PROTON NEAR-THRESHOLD

The electric dipole amplitude E(0+) for p(gamma, pi(0))p near threshol d has been extracted from the experimental data by fitting the total c ross section in high energy region, E(g)amma > 160 MeV. The result is (-1.56+/-0.10)x10(-3) m(pi+)(-1). This amplitude is calculated by taki ng the vector mesons into account in the pole model of t-channel. Our analysis manifests a favor of negative sign for the rho pi gamma coupl ing constant.