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Measurement of prompt J/ψ and beauty hadron production cross sections at mid-rapidity in pp collisions at \( \sqrt{s}=7 \) TeV

Abstract

The ALICE experiment at the LHC has studied J/ψ production at mid-rapidity in pp collisions at \( \sqrt{s}=7 \) 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 χc resonances, is σprompt 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.) μb. 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 \( {\sigma_{{{J \left/ {{\psi \leftarrow {{\mathrm{h}}_{\mathrm{B}}}}} \right.}}}} \) (p t > 1.3 GeV/c, |y| < 0.9) = 1.46 ± 0.38 (stat.) \( _{-0.32}^{+0.26 } \) (syst.) μb. 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 \( \mathrm{b}\overline{\mathrm{b}} \) pair total cross section and dσ/dy at mid-rapidity.

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