production in p collisions at = 1.8

We have studied J ψ production in p p collisions at s = 1.8 TeV with the DO detector at Fermilab using μ+μ− data. We have measured the inclusive J ψ production cross section as a function of J ψ transverse momentum, pT. For the kinematic range pT > 8 GeV/c and |η| σ(p p → J ψ + X) · Br ( J ψ → μ + μ − ) = 2.08 ± 0.17( stat) ± 0.46(syst) nb. Using the muon impact parameter we have estimated the fraction of J ψ mesons coming from B meson decays to be fb = 0.35 ± 0.09(stat)±0.10(syst) and inferred the inclusive b production cross section. From the information on the event topology the fraction of nonisolated J ψ events has been measured to be fnonisol = 0.64 ± 0.08(stat)±0.06(syst). We have also obtained the fraction of J ψ events resulting from radiative decays of χc states, fχ = 0.32 ± 0.07(stat)±0.07(syst). We discuss the implications of our measurements for charmonium production processes.