Photoproduction of η-mesons off C and Cu Nuclei for Photon Energies below 1.1 GeV(I. Nuclear Physics)

The η-meson photoproduction cross sections have been measured on C and Cu targets for photon energies between 600 and 1100MeV to investigate the behavior of the S_11 (1535) resonance in a nucleus. The excitation functions of the cross section as well as angular and momentum distributions of η-mesons are in quantitative agreement with Quantum Molecular Dynamics (QMD) model calculations, in which the η-meson emission processes other than the S_11 (1535) resonance are also incorporated as proposed in the η-MAID model. It is shown that the excitation of the D_15 (1675) resonance might play an important role for E_γ>900MeV