Polarization Observables in $\phi$-Meson Photoproduction and the Strangeness Content of the Proton

The contributions of direct knockout processes, in addition to the diffractive production and one-pion-exchange processes associated with the $\phi \rho \pi$ and $\phi \gamma \pi$ couplings, to the polarization observables of the $\phi$ photoproduction from proton are calculated. We make use of the Pomeron-photon analogy and of a relativistic harmonic oscillator quark model. We find that some of the double polarization observables are very sensitive to a possible $s\overline{s}$ admixture in the proton. It arises from the difference in the spin structures of the three different amplitudes. This suggests that such measurements could be very useful to probe the strangeness content in the proton.