Study of the chi(c0) (1P(0)-3) state of charmonium formed in anti-p p annihilations

The resonance parameters of chi(c0) the 1(3)P(0) resonance of charmonium, have been measured at the Fermilab Antiproton Accumulator by means of the reaction (p) over bar p --> chi(c0) --> gamma J/psi --> gamma(e(+)e(-)). The results are M(chi(c0)) = 3417.4(-1.9)(+1.8) +/- 0.2 MeV/c(2), Gamma(chi(c0)) = 16.6(-3.7)(+5.2) +/- 0.1 MeV, and Gamma(chi(c0) --> (p) over bar p) x B(chi(c0) --> J/psi gamma) x B(J/psi --> e(+)e(-)) = 2.89(-0.53)(+0.67) +/- 0.14 eV. Using known branching ratios we also obtain Gamma(chi(c0) --> (p) over bar p) = 8.0(-1.5)(-1.9)(+1.9)(+3.5) keV. These results are discussed in relation to the other chi(cJ) states and to theoretical predictions.