Exotic hadrons and SU ( 3 ) chiral dynamics

We explore a possibility to generate exotic hadrons dynamically in the scattering of hadrons. The s-wave scattering amplitude of an arbitrary hadron with the Nambu-Goldstone boson is constructed so as to satisfy the unitarity condition and the chiral low energy theorem. We find that the chiral interaction for the exotic channels is in most cases repulsive, and that the strength of the possible attractive interaction is uniquely determined. We show that the attractive interaction in exotic channels is not strong enough to generate a bound state, while the interaction in nonexotic channel generate bound states which are considered to be the origin of some resonances observed in nature. Strong interaction of QCD exhibits rich spectra of hadrons in the nonperturvative vacuum at low energy, where about 300 hadronic states have been identified [1]. It is important to investigate the properties of hadrons to understand the low energy dynamics of QCD. Chiral symmetry provides us a way to study hadron properties in connection with the fundamental theory of QCD. Dynamical models based on chiral symmetry, known as chiral unitary approach, successfully describe the two-body scattering of hadrons with the Nambu-Goldstone (NG) bosons in coupled channels, dynamically generating some s-wave resonances in the scattering [2–5]. These studies are along the same line with the coupled-channel dynamical models for the mesonbaryon scattering studied in 60’s, where the vector meson exchange interaction was adopted. This phenomenological interaction is now identified as E-mail address: [email protected]