Compositeness of hadrons and its application to baryon resonances

In this talk, we discuss the nature of excited baryons from the viewpoint of compositeness. Compositeness is a quantitative measure of the internal structure of hadrons, originally introduced to demonstrate the composite nature of the deuteron [1,2]. In particular, the compositeness of the near-threshold states can be model-independently determined by the experimental observables [1,3,4]. Inspired by recent findings of exotic hadrons, there has been a renewed interest in compositeness within hadron spectroscopy. For such applications, it is important to characterize the compositeness of an unstable resonance, which is described by the pole of the scattering amplitude [3]. We show a couple of applications of compositeness to baryon resonances in the strangeness S=-1 [5] and S=0 [6] sectors and present future prospects in relation to experiments.

[1] S. Weinberg, Phys. Rev. 137, B672 (1965).

[2] T. Hyodo, Int. J. Mod. Phys. A 28, 1330045 (2013).

[3] Y. Kamiya, T. Hyodo, Phys. Rev. C 93, 053203 (2016); PTEP 2017, 023 (2017).

[4] T. Kinugawa, T. Hyodo, Phys. Rev. C 106, 015205 (2022).

[5] T. Sekihara, T. Hyodo, D. Jido, Phys. Rev. C93, 035204 (2016).

[6] T. Sekihara, T. Arai, J. Yamagata-Sekihara, S. Yasui, Phys. Rev. C93, 035204 (2016).