Analysis of resonance multipoles from polarization observables in η photoproduction

A combined analysis of new eta photoproduction data for total and differential cross sections, target asymmetry, and photon asymmetry is presented. Using a few reasonable assumptions we perform the first model-independent analysis of the E0+, E2-, and M2- eta photoproduction multipoles. Making use of the well-known A3/2 helicity amplitude of the D13(1520) state, we extract its branching ratio to the ηN channel, ΓηN/Γ=(0.08±0.01)%. At higher energies, we show that the photon asymmetry is extremely sensitive to small multipoles that are excited by photons in the helicity 3/2 state. The new GRAAL photon asymmetry data at higher energy show a clear signal of the F15(1680) excitation which permits extracting an F15(1680)→ηN branching ratio of (0.15-0.10+0.35)%. copyright 1999 The American Physical Society