Spin effects and baryon resonance dynamics in phi-meson photoproduction at few GeV

Abstract

The diffractive $\phi$-meson photoproduction amplitude is dominated by the Pomeron exchange process and contains the terms that govern the spin-spin and spin-orbital interactions. We show that these terms are responsible for the spin-flip transitions at forward photoproduction angles and appear in the angular distributions of $\phi\to K^+K^-$ -decay in reactions with unpolarized and polarized photon beams. At large momentum transfers, the main contribution to the $\phi$-meson photoproduction is found to be due to the excitation of nucleon resonances. Combined analysis of $\omega$ and $\phi$ photoproduction indicates strong OZI-rule violation in $\phi NN^*$ - couplings. We also show that the spin observables are sensitive to the dynamics of $\phi$-meson photoproduction at large angles and could help distinguish different theoretical models of nucleon resonances. Predictions for spin effects in $\phi$-meson photoproduction are presented for future experimental tests.