Okubo-Zweig-Iizuka rule violation in photoproduction
  We investigate OZI rule violation in omega and phi-meson photoproduction off nucleons. Data on the total cross sections indicate a large phi/omega ratio of about 0.8 at the maximal available photon energy that is in good agreement with expectations from QCD. On the other hand, data at large four momentum transfer exhibit a ratio of about 0.07, showing that the perturbative QCD regime is not approached at |t| > 2 GeV^2 and photon energies E_\gamma < 4 GeV. The anomanously large phi/omega ratio at low energies, that is close to the reaction threshold, remains to be explained within nonperturbative QCD. 
A. Sibirtsev (Bonn U.), Ulf-G. Mei{\ss}ner (Bonn U. and FZ J\"ulich),   and A.W. Thomas (Jefferson Lab)