Non-perturbative gluons in diffractive photo-production of J/psi

The modifications induced in the calculation of the cross section of the di ffractive process gamma gamma --> J/psiJ/psi, when the gluon propagator is changed are analyzed. Instead of the usual perturbative gluon propagator, a lternative forms obtained using nonperturbative methods like Dyson-Schwinge r equations are used to consider in a more consistent way the contributions of the infrared region. The result shows a reduction in the differential c ross-section for low momentum transfer once compared with the perturbative result, to be confirmed with future experimental results from TESLA. (C) 20 01 Elsevier Science B.V. All rights reserved.