The color evaporation model in diffractive J/psi photoproduction

Our goal is the study of color effects on the J/psi and D mesons production , as well as the study of their elastic production. We use the color evapor ation model (CEM), where a single factor takes into account the probability that the c (c) over bar produced in a color octet state turns into a physi cal (colorless) quarkonium or continues as a color octet, producing open ch arm. The main result of this work, besides investigating the range of appli cability of the GEM, is to show that this model can be used to describe the elastic processes of J/psi and open charm photoproduction without the use of a Pomeron. (C) 1999 Published by Elsevier Science B.V. All rights reserv ed.