Recent data compel us to interpret several peaks in the cross section of $e^{-}{e}^{+}$ annihilation into hadrons as being due to the production of four-quark molecules, i.e., resonances between two charmed mesons. A rich spectroscopy of such states is predicted and may be studied in $e^{-}{e}^{+}$ annihilation.

• Received 23 November 1976

DOI:https://doi.org/10.1103/PhysRevLett.38.317