A new N∗(1675) resonance in the γN→ηN reaction

We study the η-photoproduction focusing on the new nucleon resonance which was observed at s=1675MeV with a narrow decay width (∼10MeV) in the recent GRAAL experiment. Using an effective Lagrangian approach, we compute differential cross sections for the η-photoproduction. In addition to N∗(1675), we employ three other nucleon resonances, i.e., N∗(1535), N∗(1650) and N∗(1710), and vector meson exchanges which are the most relevant ones to this reaction process. As a result, we can reproduce the GRAAL data qualitatively well and observe obvious isospin asymmetry between the transition magnetic moments of N∗(1675): μγnn∗≫μγpp∗.