  At forward angles, the cross-sections of photoproduction of vector mesons
($\rho$, $\omega$, and $\phi$) are well accounted for by the exchange of the
Pomeron at high energies, while contributions of $t$ channel exchange of
Reggeons are significant at low energies. At large angles, the impact parameter
becomes small enough to prevent their constituents to build up the exchanged
Reggeons or Pomeron. Two gluon exchange appears to dominate above $-t\simeq 1$
GeV$^2$, especially in the $\phi$ channel.
