Existing intermediate and high energy $\phi$-photoproduction data is consistent with purely diffractive production (i.e., Pomeron exchange). However, near threshold $(1.574\mathrm{}\hspace{0.5em}\mathrm{GeV}<E_{\gamma }^{\mathrm{lab}}<~2.0\hspace{0.5em}\mathrm{GeV})$ the energy dependence of the diffractive amplitude is not well known and nondiffractive amplitudes such as ${\pi }^0$ and $\eta$ exchange, $s\overline{s}$ knockout, and nonzero $\phi \mathrm{NN}$ couplings can give sizable contributions to the cross section and polarization density matrix elements of the $\overrightarrow{\phi }{K}^{+}{K}^{-}$ decay angular distribution. We stress the importance of measurements with linearly polarized photons near the $\phi$ threshold to separate natural and unnatural parity exchange mechanisms. Approved and planned $\phi$ photoproduction and electroproduction experiments at Jefferson Lab will help establish the relative dynamical contributions near threshold and clarify outstanding theoretical issues related to apparent Okubo-Zweig-Iizuka violations.

• Received 15 September 1997

DOI:https://doi.org/10.1103/PhysRevC.57.223