Photoproduction of Η-Mesons off C and Cu Nuclei for Photon Energies below 1.1 GeV

The η-meson photoproduction cross sections have been measured on C and Cu targets for the photon energies between 600 and 1100 MeV to investigate the behavior of the S11(1535) resonance in a nucleus. The excitation functions of the cross section as well as the angular and momentum distributions of η-mesons are in quantitative agreement with the Quantum Molecular Dynamics (QMD) model calculations in which the η-meson emission processes other than the S11(1535) resonance are also incorporated. It is shown that the η production in the γN→πηN reaction and the D15(1675) resonance formation in the γn→ηn reaction play an important role for Eγ>900MeV.