We report new measurements for the mass, width, and branching ratios for the Jψ and the ψ′. These charmonium states are formed exclusively in p̄p 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 Jψ and ψ′ are Γ(Jψ)=99126 keV and Γ(ψ′)= 3063616 keV, and that the mass of the Jψ is 3096.87 0.03 MeV/c2. For the Jψ we obtain B(Jψ→p̄p)B(Jψ→e+e-)=(1.14-0.12+0.160.10) ×10-4; for the ψ′ we obtain B(ψ′→p̄p) [B(ψ′→e+e-)+B(ψ′→JψX)B(Jψ→e+e-)]=(1. 17-0.12+0.140.08)×10-5.
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)