Eta photoproduction in a combined analysis of pion- and photon-induced reactions

Understand

The $\eta N$ final state is isospin-selective and thus provides access to the spectrum of excited nucleons without being affected by excited $\Delta$ states.

• To this end, the world database on eta photoproduction off the proton up to a center-of-mass energy of $E\sim 2.3$ GeV is analyzed, including data on differential cross sections, and single and double polarization observables.
• The resonance spectrum and its properties are determined in a combined analysis of eta and pion photoproduction off the proton together with the reactions $\pi N\to \pi N$, $\eta N$, $K\Lambda$ and $K\Sigma$.
• For the analysis, the so-called J\"ulich coupled-channel framework is used, incorporating unitarity, analyticity, and effective three-body channels.