Dynamical picture for the exotic XYZ states

Abstract

We present a dynamical approach for description of the multi-quark states that is based on an effective interaction Lagrangian describing the coupling of hadrons to their constituent quarks. First, we explore the consequences of treating the X(3872) meson as a tetraquark bound state. We calculate the decay widths of the observed channels and conclude that for reasonable values of the size parameter of the X(3872) one finds consistency with the available experimental data. Then we have critically checked the tetraquark picture for the Zc(3900) state by analyzing its strong decays. We found that Zc(3900) has a much more stronger coupling to DD* than to J/Ψπ that is in discord with experiment. As an alternative we have employed a molecular-type four-quark current to describe the decays of the Zc(3900) state as the charged particle in the isotriplet. We found that a molecular-type current gives the values of the above decays in accordance with the experimental observation. By using moleculartype four-quark currents for the recently observed resonances Zb(10610) and Zb(10650), we have calculated their two-body decay rates into a bottomonium state plus a light meson as well as into B-meson pairs.