Eta-photoproduction in a gauge-invariant chiral unitary framework

TL;DR

This paper develops a gauge-invariant chiral unitary model to analyze eta meson photoproduction off protons, successfully describing recent experimental data and extracting the S11(1535) resonance pole.

Contribution

It introduces a gauge-invariant chiral unitary approach for eta photoproduction, deriving the interaction kernel from leading order chiral Lagrangian and applying it to experimental data.

Findings

Accurately describes recent threshold data from MAMI

Extracts the complex pole of the S11(1535) resonance

Discusses extensions of the interaction kernel

Abstract

We analyse photoproduction of eta mesons off the proton in a gauge-invariant chiral unitary framework. The interaction kernel for meson-baryon scattering is derived from the leading order chiral effective Lagrangian and iterated in a Bethe-Salpeter equation. The recent precise threshold data from the Crystal Ball at MAMI can be described rather well and the complex pole corresponding to the S11(1535) is extracted. An extension of the kernel is also discussed.