Discovery of a Narrow Resonance ine+e−Annihilation

We have observed a very sharp peak in the cross section for ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\mathrm{hadrons}, {e}^{+}{e}^{\ensuremath{-}}$, and possibly ${\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ at a center-of-mass energy of 3.105\ifmmode\pm\else\textpm\fi{}0.003 GeV. The upper limit to the full width at half-maximum is 1.3 MeV.