The resonance parameters of ${\chi }_{c0\mathrm{}}$, the ${}_{}{}^3{}_{}{}^{}1P_0^{}{}_{}{}^{}$ resonance of charmonium, have been measured at the Fermilab Antiproton Accumulator by means of the reaction $\overline{p}p\to {\chi }_{c0\mathrm{}}\to \gamma J/\psi \to \gamma \left(e^{+}{e}^{-}\right)$. The results are $M\left({\chi }_{c0\mathrm{}}\right){=3417.4\mathrm{}}_{-1.9\mathrm{}}^{+1.8\mathrm{}}\pm 0.2\mathrm{MeV}{/c}^2$, $\Gamma \left({\chi }_{c0\mathrm{}}\right){=16.6\mathrm{}}_{-3.7\mathrm{}}^{+5.2\mathrm{}}\pm 0.1\mathrm{MeV}$, and $\Gamma ({\chi }_{c0\mathrm{}}\to \overline{p}p)\times B({\chi }_{c0\mathrm{}}\to J/\psi \gamma )\times B(J/\psi \to e^{+}{e}^{-}){=2.89\mathrm{}}_{-0.53\mathrm{}}^{+0.67\mathrm{}}\pm 0.14\mathrm{eV}$. Using known branching ratios we also obtain $\Gamma ({\chi }_{c0\mathrm{}}\to \overline{p}p){=8.0\mathrm{}}_{-1.5-1.9\mathrm{}}^{+1.9+3.5\mathrm{}}\mathrm{keV}$. These results are discussed in relation to the other ${\chi }_{\mathrm{cJ}}$ states and to theoretical predictions.

• Received 3 June 1999

DOI:https://doi.org/10.1103/PhysRevLett.83.2902