On the nature of the $N^{\ast }$ and $\Delta$ resonances via coupled-channel dynamics

Abstract

This talk focuses on a recent work aiming at determining the composition of certain $N^{\ast }$ and $\Delta$ resonances, i.e. whether they are compact states formed directly by quarks and gluons, or composite generated from the meson-baryon interaction. The information of the resonance poles is provided by a comprehensive coupled-channel approach, the Jülich-Bonn model. Thirteen 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 eight 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.

Comments: 6 pages, 2 figures, 16th International Conference on Meson-Nucleon Physics and the Structure of the Nucleon (MENU 2023), text overlaps with arXiv:2307.06799 [nucl-th]