Using an improved Breit-Wigner model, the paper argues that complex pole residues are amplitude-level quantities, and shows how multi-resonance interference can make the Delta(1232) partial width appear to exceed its total width.
Light baryon resonances from a coupled-channel study including $\mathbf{K\Sigma}$ photoproduction
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abstract
The J\"ulich-Bonn dynamical coupled-channel approach is extended to include $K\Sigma$ photoproduction off the proton. Differential cross section and (double) polarization data for $K^+\Sigma^0$ and $K^0\Sigma^+$ are analysed simultaneously with the pion- and photon-induced production of $\pi N$, $\eta N$, $K\Lambda$, and $K\Sigma$ final states, totaling more than 67,000 data points for center-of-mass energies $W<2.4$ GeV. Based on the fit results the spectrum of $N^*$ and $\Delta$ resonances is extracted in terms of pole positions and residues. We discuss the impact of the $\gamma p\to K\Sigma$ channels in detail and investigate the influence of recent polarization data for $\eta p$ photoproduction.
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Resolving the $\Delta(1232)$ partial width anomaly: Complex pole residue is not a fundamental resonance property
Using an improved Breit-Wigner model, the paper argues that complex pole residues are amplitude-level quantities, and shows how multi-resonance interference can make the Delta(1232) partial width appear to exceed its total width.