Exclusive photo- and electroproduction of vector mesons at large momentum transfer

Two-gluon-exchange mechanisms are expected to govern exclusive photo- and electro-production of vector mesons at large momentum transfer. While quark-interchange mechanisms may compete, at least at low energies, in the light-quark sector, they are strongly suppressed in the heavy-quark sector. Phi-meson production appears to be a promising way to study these two-gluon-exchange mechanisms. On the one hand, they appear to be a good candidate to explain the hard part of the pomeron. On the other hand, they open up an almost virgin field: the study of quark correlations in hadronic matter. A possible application would be the study of hidden color components in the wave function of the ground state of few-nucleon systems.