The impact of $\mathbf{K^+\Lambda}$ photoproduction on the resonance spectrum

TL;DR

This paper extends a coupled-channel framework to include $K^+\Lambda$ photoproduction, analyzing extensive data to refine the nucleon and $ riangle$ resonance spectrum and identify new states.

Contribution

It introduces an extended Jülich-Bonn model incorporating $K^+\Lambda$ photoproduction with unitarity and analyticity, enabling more accurate resonance spectrum extraction.

Findings

Resonance parameters are significantly influenced by the $K^+\Lambda$ channel.

New resonance states not observed in other channels are identified.

The model successfully fits over 40,000 data points up to 2.3 GeV.

Abstract

The J\"ulich-Bonn coupled-channel framework is extended to $K^+\Lambda$ photoproduction. The spectrum of nucleon and $\Delta$ resonances is extracted from simultaneous fits to several pion-induced reactions in addition to pion, eta and $K^+\Lambda$ photoproduction off the proton. More than 40,000 data points up to a center-of-mass energy of E$\sim$2.3 GeV including recently measured double-polarization observables are analyzed. The influence of the $\gamma p\to K^+\Lambda$ channel on the extracted resonance parameters and the appearance of states not seen in other channels is investigated. The J\"ulich-Bonn model includes effective three-body channels and guarantees unitarity and analyticity, which is a prerequisite for a reliable determination of the resonance spectrum in terms of poles and residues.