Diffractive J/Psi production in high energy gamma-gamma collisions as a   probe of the QCD pomeron
  The reaction \gamma\gamma ---> J/Psi J/Psi is discussed assuming dominance of the QCD BFKL pomeron exchange. We give prediction for the cross-section of this process for LEP2 and TESLA energies. We solve the BFKL equation in the non-forward configuration taking into account dominant non-leading effects which come from the requirement that the virtuality of the exchanged gluons along the gluon ladder is controlled by their transverse momentum squared. We compare our results with those corresponding to the simple two gluon exchange mechanism and with the BFKL pomeron exchange in the leading logarithmic approximation. The BFKL effects are found to generate a steeper t-dependence than the two gluon exchange. The cross-section is found to increase with increasing CM energy W as (W^2)^{2\lambda}. The parameter \lambda is slowly varying with W and takes the values lambda \sim 0.23 - 0.28. The magnitude of the total cross-section for the process \gamma\gamma --> J/Psi J/Psi is found to increase from 4 to 26 pb within the energy range accessible at LEP2. The magnitude of the total cross-section for the process e^+e^- ---> e^+e^- J/Psi J/Psi with antitagged e^+ and e^- is estimated to be around 0.1 pb at LEP2. 
Jan Kwiecinski (1) and Leszek Motyka (2) ((1) H. Niewodniczanski   Institute of Nuclear Physics, Cracow, Poland (2) Jagellon...