Effects of nucleon resonances on $\eta$ photoproduction off the neutron reexamined

Abstract

We investigate $\eta$ photoproduction off the neutron target, i.e., $\gamma n\to \eta n$, employing an effective Lagrangian method combining with a Regge approach. As a background, we consider nucleon exchange in the $s$-channel diagram and $\rho$- and $\omega$-meson Regge trajectories in the $t$ channel. The role of nucleon resonances given in the Review of Particle Data Group in the range of $W\approx 1500-2100$ 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 ${\sigma }_{1/2}$, ${\sigma }_{3/2}$ are found to be in qualitative agreement with the recent A2 experimental data. The predictions of the beam asymmetry are also given.

Comments: 12 pages, 6 figures