The structure of the photoproduction amplitude in the region is analyzed based on Pomeron-exchange and meson-exchange mechanisms. The SU(3) symmetry and the decay widths are exploited to determine the parameters that are needed to predict the amplitudes due to pseudoscalar mesons exchange, scalar mesons exchange, and the radiation from the nucleon. In addition to the universally accepted Pomeron exchange with an intercept we investigate the role of a second Pomeron with as inspired by the glueball predicted by the lattice QCD calculation and dual Ginsburg-Landau model. It is found that the existing limited data at low energies near threshold can accommodate either the second Pomeron or the scalar mesons exchange. The differences between these two competing mechanisms are shown to have profound effects on various density matrices which can be used to calculate the cross sections as well as various single and double polarization observables. We predict a definite isotopic effect: polarization observables of photoproduction on the proton and neutron targets can have differences of a factor 2 and more.
- Received 8 March 1999
- Published 29 July 1999
© 1999 The American Physical Society