Nature of the $N^*$ and $\Delta$ resonances via coupled-channel dynamics

TL;DR

This study uses a coupled-channel approach to analyze the composition of $N^*$ and $Delta$ resonances, distinguishing between quark-gluon states and hadronic molecules, with findings indicating the nature of specific resonances.

Contribution

It provides a systematic analysis of resonance compositions using the Jülich-Bonn coupled-channel model, offering clearer insights into the structure of multiple baryonic resonances.

Findings

Eight resonances are identified as likely composite states.

Four resonances are identified as likely compact states.

Model comparisons help estimate uncertainties in the conclusions.

Abstract

This work aims at determining the composition of certain $N^*$ and $\Delta$ resonances, i.e. whether they are compact states formed directly by quarks and gluons, or hadronic molecules generated from the meson-baryon interaction. The information of the resonance poles is provided by a comprehensive coupled-channel approach, the J\"{u}lich-Bonn model. $13$ states that are significant in this approach are studied. Two criteria for each state are adopted in this paper, the comparison thereof roughly indicates the model uncertainties. It is found that the conclusions for $8$ resonances are relatively certain: $N(1535) \frac{1}{2}^-$, $N(1440) \frac{1}{2}^+$, $N(1710) \frac{1}{2}^+$, and $N(1520) \frac{3}{2}^-$ tend to be composite; whereas $N(1650) \frac{1}{2}^-$, $N(1900) \frac{3}{2}^+$, $N(1680) \frac{5}{2}^+$, and $\Delta(1600) \frac{3}{2}^+$ tend to be compact.