Nonlinearity of vacuum Reggeons and exclusive diffractive production of vector mesons at HERA

The processes of exclusive photo- and electroproduction of vector mesons rho(0)(770), phi(1020), and J/psi(3096) at collision energies 30 GeV < W < 300 GeV and transferred momenta squared 0 <-t < 2 GeV2 are considered in the framework of a phenomenological Regge-eikonal scheme with nonlinear Regge trajectories in which their QCD asymptotic behavior is taken into account explicitly. By comparison of available experimental data from ZEUS and H1 Collaborations with the model predictions it is demonstrated that corresponding angular distributions and integrated cross sections in the above-mentioned kinematical range can be quantitatively described with use of two C-even vacuum Regge trajectories. These are the "soft" Pomeron dominating the high-energy reactions without a hard scale and the "hard" Pomeron giving an essential contribution to photo- and electroproduction of heavy vector mesons and deeply virtual electroproduction of light vector mesons.