We have studied the 3PJ (χc) states of charmonium in formation by antiproton-proton annihilations in experiment E835 at the Fermi lab Antiproton Source. We report new measurements of the mass, width, and B(χcJ → p̄p) Γ (χcJ → J/ψ + anything) for the χc1 and χc2 by means of the inclusive reaction p̄p → χcJ → J/ψ + anything → (e+e-) + anything. Using the subsample of events where χcJ → γ + (e+e-) is fully reconstructed, we derive B(χcJ → p̄p) Γ (χcJ → J/ψ + γ). We summarize the results of the E760 (updated) and E835 measurements of mass, width and B (χcJ → p̄p) Γ (χcJ → J/ψ + γ) (J = 0, 1, 2) and discuss the significance of these measurements.
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We gratefully acknowledge the support of the Fermilab staff and technicians and especially the Antiproton Source Department of the Accelerator Division and the On-Line Department of the Computing Division. We wish to thank also the INFN and university technicians and engineers from Ferrara, Genova, Torino and Northwestern for the valuable work done. This research was supported by the Italian Istituto Nazionale di Fisica Nucleare (INFN) and US Department of Energy.