On eta photoproduction on the neutron and pi^0 eta photoproduction

TL;DR

This paper models eta photoproduction on the neutron and pi^0 eta photoproduction, explaining recent experimental enhancements and polarization measurements through coupled channels and resonance dynamics.

Contribution

It provides a theoretical explanation for the eta photoproduction enhancement and polarization observables using an SU(3) coupled channels model and chiral unitary approach.

Findings

Quantitative explanation of neutron and proton eta photoproduction cross sections.

Identification of the Delta(1700)D33 resonance's role in eta production.

Confirmation of the dynamical nature of the Delta(1700)D33 resonance.

Abstract

The recently discovered enhancement of eta photoproduction on the quasi-free neutron at energies around s^1/2 ~ 1.67 GeV is addressed within an SU(3) coupled channels model. The K Sigma threshold plays a significant role and the quasi-free cross sections on proton and neutron, sigma_n and sigma_p, can be quantitatively explained. For the reaction gamma p --> pi^0 eta p, we evaluate the polarization observables I^S and I^C from a chiral unitary amplitude developed earlier. The I^S and I^C observables have been recently measured for the first time by the CBELSA/TAPS collaboration. We show the significance of the Delta(1700)D33 resonance and its S-wave decay into eta Delta(1232) which further confirms the dynamical nature of this resonance.