Nucleonic resonance effects in the $Ï$ meson photoproduction
arXiv:nucl-th/9906013 · doi:10.1016/S0375-9474(99)00398-X
Abstract
The process $γp \to Ïp$ close to threshold is investigated focusing on the role played by the {\it s}- and {\it u}-channel nucleonic resonances. For this purpose, a recent quark model approach, based on the $SU(6)\otimes O(3)$ symmetry with an effective Lagrangian, is extended to the $Ï$ meson photoproduction. Another non-diffractive process, the {\it t}-channel $Ï^0$ exchange, is also included. The diffractive contribution is produced by the {\it t}-channel Pomeron exchange. Contributions from non-diffractive {\it s}- and {\it u}-channel process are found small in the case of cross sections and polarization observables at forward angles. However, backward angle polarization asymmetries show high sensitivity to this non-diffractive process. Different prescriptions to keep gauge invariance for the Pomeron exchange amplitudes are investigated. Possible deviations from the exact $SU(6)\otimes O(3)$ symmetry, due to the configuration mixing, are also discussed.
34 pages, 16 figures, to appear in Nucl. Phys. A