Measurement of the resonance parameters of the χ1(13P1) and χ2(13P2) states of charmonium formed in antiproton–proton annihilations

We have studied the 3PJ (χc) states of charmonium in formation by antiproton–proton annihilations in experiment E835 at the Fermilab Antiproton Source. We report new measurements of the mass, width, and B(χcJ→p¯p)Γ(χcJ→J/ψ+anything) for the χc1 and χc2 by means of the inclusive reaction p¯p→χcJ→J/ψ+anything→(e+e−)+anything. Using the subsample of events where χcJ→γ+J/ψ→γ+(e+e−) is fully reconstructed, we derive B(χcJ→p¯p)Γ(χcJ→J/ψ+γ). We summarize the results of the E760 (updated) and E835 measurements of mass, width and B(χcJ→p¯p)Γ(χcJ→J/ψ+γ) (J=0,1,2) and discuss the significance of these measurements.