MEASUREMENT OF THE J/PSI AND PSI' RESONANCE PARAMETERS IN (P)OVER-BAR ANNIHILATION

We report new measurements for the mass, width, and branching ratios for the J/psi and the psi'. These charmonium states are formed exclusively in ppBAR annihilations at the Fermilab Antiproton Accumulator ring, where stochastically cooled antiprotons are brought into collision with the protons of an internal hydrogen gas jet target. The antiproton energy is precisely controlled and measured allowing an accurate measurement of the resonance parameters. From the shape of the excitation curves we find that the widths of J/psi and psi' are GAMMA(J/psi) = 99 +/- 12 +/- 6 keV and GAMMA(psi')=306+/-36+/-16 keV, and that the mass of the J/psi is 3096.87 +/- 0.03 +/- 0.03 MeV/c2. For the J/psi we obtain B(J/psi --> ppBAR)B(J/psi --> e+e-) = (1.14(-0.12)+0.16 +/- 0.10) x 10(-4); for the psi' we obtain B(psi' --> ppBAR)[B(psi' --> e+e-) + B(psi' --> J/psiX)B(J/psi --> e+e-)] = (1.17(-0.12)+0.14 +/- 0.08) x 10(-5).