Implications of heavy-quark spin symmetry on heavy-meson hadronic molecules

In recent years, many heavy mesons and charmonia were observed which do not fit in the conventional quark model expectations. Some of them are proposed to be hadronic molecules. Here we investigate the consequences of heavy-quark spin symmetry on these heavy-meson hadronic molecules. Heavy-quark spin symmetry enables us to predict new heavy-meson molecules and provides us with a method to test heavy-meson molecule assumptions of some newly observed states. In particular, we predict an eta_{c};{'}f_{0}(980) bound state as the spin-doublet partner of the Y(4660) proposed as a psi;{'}f_{0}(980) bound state with a mass of 4616_{-6};{+5} MeV and the prominent decay mode eta_{c};{'}pipi. The width is predicted to be Gamma(eta_{c};{'}pipi) = 60 +/- 30 MeV. The pi;{+}pi;{-} invariant mass spectrum and the line shape are calculated. We suggest searching for this state in B;{+/-} --> eta_{c};{'}K;{+/-}pi;{+}pi;{-}, whose branching fraction is expected to be large.