J/psi-photoproduction and the gluon structure of the nucleon

Using QCD sum rule method based on the operator product expansion, we calcu late the J/psi photoproduction cross section in terms of the gluon distribu tion function of the nucleon. Comparing the results with the data, we show that experimental behaviour of the cross section correctly reflects the x-d ependence of the gluon distribution obtained from deep inelastic scattering .