Electromagnetic transition amplitude for Roper resonance from holographic QCD

Fujii, Daisuke; Iwanaka, Akihiro*; Hosaka, Atsushi*

The Roper resonance, the first excited state of the nucleon, is one of the best established baryon resonates. Yet, its properties have not been consistently explained by effective models of QCD, such as the non-relativistic quark model. In this paper, we propose an alternative approach in the Sakai-Sugimoto model that is one of the holographic models of QCD. In particular, we analyze the helicity amplitude of the electromagnetic transitions at the leading of 't Hooft coupling . The model incorporates baryon structure at short distance by nonlinear mesons surrounded by meson clouds at long distance. We demonstrate that the recently observed data by CLAS are explained in the present approach.