Nucleonic resonance effects in the phi meson photoproduction

The process gamma p --> phi p close to threshold is investigated focusing o n the role played by the sand u-channel nucleonic resonances. For this purp ose, a recent quark model approach, based on the SU(6) x O(3) symmetry with an effective Lagrangian, is extended to the phi meson photoproduction. Ano ther non-diffractive process, the t-channel pi(0) exchange, is also include d. The diffractive contribution is produced by the t-channel Pomeron exchan ge. Contributions from non-diffractive s- and u-channel processes are found small in the case of cross sections and polarization observables at forwar d angles. However, backward angle polarization asymmetries show high sensit ivity to this non-diffractive process. Different prescriptions to keep gaug e invariance for the Pomeron exchange amplitudes are investigated. Possible deviations from the exact SU(6) x O(3) symmetry, due to the configuration mixing, are also discussed. (C) 1999 Elsevier Science B.V. All rights reser ved.