Rescattering effects in coherent η-photoproduction on the deuteron

Rescattering effects in coherent eta photoproduction on the deuteron are studied in the region of the S-11(1535) resonance. For the elementary reaction mechanism on the nucleon, an effective isobar model with inclusion of resonances and Born terms is used. The resonance parameters are fixed by considering pion photoproduction only. The predicted cross sections for eta production on the proton are in satisfactory agreement with experiment without any additional parameter fitting. For the coherent eta production on the deuteron we have considered the impulse approximation taking into account the P-11(1440), D-13(1520), and S-11(1535) resonances, rescattering, and meson exchange currents. For the rescattering mechanism a coupled channel model including the dominant S-11(1535) resonance is used. A reduction of the total cross section up to about 50% through rescattering is found. This is considered as an upper limit for the size of rescattering effects due to uncertainties in the NS11 transition potential. Other two-body effects like meson exchange currents appear to be small. (C) 1999 Elsevier Science B.V. All rights reserved.