S-11(1535) Resonance In Nuclei

In order to study the S-11 (1535) resonance in the nuclear medium, total cross sections of the (gamma, eta) reactions on C, Al and Cu have been measured for photon energies between 680 and 1000 MeV. A broad resonance structure due to the excitation and decay of the S11 resonance in the nucleus has been clearly observed for the first time. The apparent energy and width of the resonance are 900 and 300 McV, respectively. Model calculations based on the quantum molecular dynamics (QMD) have been performed. The eta photoproduction on nuclei can be basically understood as the quasi-free reaction with the reasonable medium modifications.