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

We analyze the process e p --> e p phi near the threshold within the uud-s (s) over bar cluster model as a probe of the strangeness content of the 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 the vector-meson-dominance model when only a 3-5% strange quark admixture is assumed, which should be compared with 10-20% of the non-relativistic quark model prediction. The cross sections of the uud- and s (s) over bar knockout processes have qualitatively different dependences on the 4-momentum transfer squared to the proton and may be distinguished experimentally. We also discuss briefly a way to determine the strangeness content of the proton in the 5-quark cluster model. (C) 1997 Elsevier Science B.V.