Exotic resonances due to η exchange

The meson X(3872)X(3872) and several related states appear to be in large part hadronic molecules in which a heavy flavored meson (e.g., D0D0) is bound to another heavy meson (e.g., D¯⁎0). Although not the only contribution to the binding, pion exchange seems to play a crucial role in generating the longest-range force between constituents. Mesons without u and d   light quarks (such as DsDs) cannot exchange pions, but under suitable conditions can bind as a result of η   exchange. Channels in which this mechanism is possible are identified, and suggestions are made for searches for the corresponding molecular states, including a manifestly exotic baryonic ΛcD¯s⁎ resonance decaying into J/ψΛ.