In-medium effects in Eta photo-production through the S-11 resonance in the relativistic approach

摘要

In-medium effects in photon excitation of the Si, resonance from a nucleon and its decay into an q-meson are studied using the relativistic mean field approach. We examine the in-medium effects by varying the Dirac fields of the nucleon and the Si, resonance separately. We conclude that the Dirac fields of the nucleon, which reduce the nucleon effective mass, enlarge the width of the S-11 resonance, and small Dirac fields of the resonance shift the peak position. These combined effects can account for the in-medium properties observed in the experimental data for C-12(gamma,eta) reaction.