J/ψ and ψ′ production at the CERN p̄p collider

Abstract We have measured the production cross-section times branching ratio for J/ψ→μ + μ − in pp interactions at √ s = 630 GeV in the kinematic range |y| and p T >5 GeV /c, BR ( J /ψ→μ + μ − )σ( p p → J /ψ)=6.18±0.24±0.81 nb . The data sample collected in 1988 and 1989 for an integrated luminosity of 4.7 pb −1 represents a fivefold improvement over the statistics in our earlier study of the J / ψ production process, and the p T distribution which is measured extends to 28 GeV / c . Using event topology we show that the rate for the direct production of J / ψ , via radiative decays of χ states, is larger than that for production via B-hadrons. Production of ψ′ is also studied using the decay modes ψ ′→ μ + μ − and ψ ′→ J / ψπ + ψ − .