Study of the Chi-1 and Chi-2 Charmonium States Formed In (p)bar-p Annihilations

We report on a study of the chi-1(P-3(1)) and chi-2(P-3(2)) states of charmonium formed in antiproton-proton annihilations. An energy scan through the resonances, performed with a very narrow momentum-band beam of antiprotons intersecting a hydrogen jet target, enables us to perform very precise measurements of the mass and the total width of the two resonances. From a sample of 513-chi-1 and 585-chi-2 events, we find M(chi-1) = (3510.53 +/- 0. 13) MeV/c2, M(chi-2) = (3556.15 +/- 0.14) MeV/c2, GAMMA(chi-1) = (0-88 +/- 0.14) MeV and GAMMA(chi-2) = (1.98 +/- 0.18) MeV. From our measurement of the quantity GAMMA(R --> ppBAR) X BR(R --> J/psi-gamma) x BR(J/psi --> e+ e-), using known branching ratios, we obtain GAMMA(chi-1 --> ppBAR) = (69 +/- 13) eV and GAMMA(chi-2 --> ppBAR) = (180 +/- 31) eV.