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Dynamical picture for the exotic XYZ states
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 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 one finds consistency with the available
experimental data. Then we have critically checked the tetraquark picture for
the state by analyzing its strong decays. We found that
has a much more stronger coupling to than to that is in
discord with experiment. As an alternative we have employed a molecular-type
four-quark current to describe the decays of the 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 molecular-type four-quark currents for the recently
observed resonances and , we have calculated their
two-body decay rates into a bottomonium state plus a light meson as well as
into B-meson pairs.Comment: 7 pages, 4 figures, some references adde
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