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

Abstract We study the η -photoproduction focusing on the new nucleon resonance which was observed at s = 1675 MeV with a narrow decay width ( ∼ 10 MeV ) 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 ) : μ γ n n ∗ ≫ μ γ p p ∗ .