Hadron Molecules

We discuss a possible interpretation of the open charm mesons $D_{s0}^*(2317)$, $D_{s1}(2460)$ and the hidden charm mesons X(3872), Y(3940) and Y(4140) as hadron molecules. Using a phenomenological Lagrangian approach we review the strong and radiative decays of the $D_{s0}^* (2317)$ and $D_{s1}(2460)$ states. The X(3872) is assumed to consist dominantly of molecular hadronic components with an additional small admixture of a charmonium configuration. Determing the radiative ($\gamma J/\psi$ and $\gamma \psi(2s)$) and strong ($J/\psi 2\pi $ and $ J/\psi 3\pi$) decay modes we show that present experimental observation is consistent with the molecular structure assumption of the X(3872). Finally we give evidence for molecular interpretations of the Y(3940) and Y(4140) related to the observed strong decay modes $J/\psi + \omega$ or $J/\psi + \phi$, respectively.
Comment: 6 pages, Plenary talk given at the 5-th Int. Conf. on Quarks and Nuclear Physics, Beijing, September 21-26,2009