The dynamical properties of nucleon resonances by top-down approach of holographic QCD*

Due to the non-perturbative nature of low-energy QCD, we do not always understand the properties of the nucleons, the fundamental excitations created by its vacuum. To understand low-energy QCD, it is useful to investigate nucleon resonances. In this study, we investigate various properties of nucleon resonances using the Sakai-Sugimoto model, one of the holographic QCD models. It is difficult to theoretically explain the various properties of the Roper resonance, even though it is one of the most experimentally established nucleon resonances. We have attempted to calculate the properties of the Roper resonance, especially the electromagnetic transition amplitude and the decay width of the one-pion emission. We also attempted the same analysis for other nucleon resonances (Δ(1232), N<span style="font-size:10.8333px">*(1535)). For this purpose, it is necessary to obtain the wave function and chiral current of baryons in the Sakai-Sugimoto model. In the Sakai-Sugimoto model, the wave function is obtained by collective coordinate quantization of instanton (baryon). We then define the current using the GKP-Witten relation and obtain the electromagnetic transition amplitude and the decay width of the one-pion emission, which are shown to reproduce the experimental data well. The results strongly suggest that the contribution of the collective motion of mesons is important for a comprehensive understanding of nucleon resonances.