Measurement of prompt J/ψ and beauty hadron production cross sections at mid-rapidity in pp collisions at √s=7 TeV

A bstract The ALICE experiment at the LHC has studied J/ ψ production at mid-rapidity in pp collisions at √s=7 TeV through its electron pair decay on a data sample corresponding to an integrated luminosity L int = 5 . 6 nb −1 . The fraction of J/ ψ from the decay of long-lived beauty hadrons was determined for J/ ψ candidates with transverse momentum p t > 1 . 3 GeV/ c and rapidity | y | < 0 . 9. The cross section for prompt J/ ψ mesons, i.e. directly produced J/ ψ and prompt decays of heavier charmonium states such as the ψ (2S) and χ c resonances, is σ prompt J/ ψ ( p t > 1 . 3 GeV /c, | y | < 0 . 9) = 8 . 3 ± 0 . 8 (stat . ) ± 1 . 1 (syst . ) -1.4+1.5 (syst . pol . ) μ b. The cross section for the production of b-hadrons decaying to J/ ψ with p t > 1 . 3 GeV/ c and | y | < 0 . 9 is σ_J / ψ ← hB . ( p t > 1.3 GeV/ c , | y | < 0.9) = 1.46 ± 0.38 (stat.) -0.32+0.26 (syst.) μ b. The results are compared to QCD model predictions. The shape of the p t and y distributions of b-quarks predicted by perturbative QCD model calculations are used to extrapolate the measured cross section to derive the bb̄ pair total cross section and d σ/ d y at mid-rapidity.