Electroproduction of phi meson from proton and the strangeness in the nucleon

We analyze the process $e p \to e p \phi$ near the threshold within $uud - s\bar s$ cluster model as a probe of the strangeness content of proton. Our consideration is based on the relativistic harmonic oscillator quark model which takes into account the Lorentz-contraction effect of the hadron wavefunctions. We find that the knockout mechanisms are comparable to the diffractive production of vector-meson-dominance model when only (3-5)% strange quark admixture is assumed, which should be compared with (10-20)% of the nonrelativistic quark model prediction. The cross sections of the $uud$- and $s\bar s$-knockout processes have qualitatively different dependence on the four-momentum transfer squared to the proton and may be distinguished experimentally. We also briefly discuss a way to determine the strangeness content of proton in 5-quark cluster model.