Effects of nucleon resonances on η photoproduction off the neutron reexamined

Abstract

We investigate η photoproduction off the neutron target, i.e., γn → ηn, employing an effective Lagrangian method combining with a Regge approach. As a background, we consider nucleon exchange in the s-channel diagram and ρ-and ω-meson Regge trajectories in the t channel. The role of nucleon resonances given in the Review of Particle Data Group in the range of W ≈ 1500 − 2100 MeV and the narrow nucleon resonance N (1685, 1/2 + ) is extensively studied. The numerical results of the total and differential cross sections, double polarization observable E, and helicity-dependent cross sections σ 1/2 , σ 3/2 are found to be in qualitative agreement with the recent A2 experimental data. The predictions of the beam asymmetry are also given.

Light Baryon Spectroscopy

“…Following this publications, Tiator et al [259] fitted the cross section as well as the E data and could attribute this structure to an interference between different partial waves with a dominant contribution of the N (1710) 1 2 + . In contrast to this, Suh et al [260] were able to describe the data by a narrow nucleon resonance N (1685) 1 2 + . A final conclusion about this structure is still unavailable and can only be provided by additional highstatistics measurements.…”

Pion Photoproduction off Nucleon with Hamiltonian Effective Field Theory

“…In addition, the contribution from the resonance N * (1535) should be taken into account especially as the energy approaches the mass since it has the same quantum number with the S 11 πN channel. We use the following Lagrangians [10,71,81,82]…”