I suggest that the structure observed between $\sqrt{s}=3.9\mathrm{} \mathrm{and} 4.5$ GeV at SPEAR is due to the presence of exotic mesons composed of a charmed diquark and antidiquark. Arguments for the existence of such mesons are reviewed. The characteristic features, i.e., masses, narrow widths, and abundance, which enable them to explain the data are presented. Further properties and yet another narrow meson with $m\approx 6.7$ GeV/${\mathit{c}}^2$ is predicted.

• Received 22 December 1975

DOI:https://doi.org/10.1103/PhysRevLett.36.697