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

AbstractThe ALICE experiment at the LHC has studied J/ψproduction at mid-rapidity in pp collisions at$ \sqrt{s}=7 $TeV through its electron pair decay on a data sample corresponding to an integrated luminosityLint= 5.6 nb−1. The fraction of J/ψfrom the decay of long-lived beauty hadrons was determined for J/ψcandidates with transverse momentumpt>1.3 GeV/cand rapidity |y|<0.9. The cross section for prompt J/ψmesons, i.e. directly produced J/ψand prompt decays of heavier charmonium states such as theψ(2S) and χcresonances, is σprompt J/ψ(pt>1.3 GeV/c,|y|<0.9) = 8.3 ± 0.8 (stat.) ± 1.1 (syst.)$ _{-1.4}^{+1.5 } $(syst.pol.)μb. The cross section for the production of b-hadrons decaying to J/ψwithpt>1.3 GeV/cand |y|<0.9 is$ {\sigma_{{{J \left/ {{\psi \leftarrow {{\mathrm{h}}_{\mathrm{B}}}}} \right.}}}} $(pt> 1.3 GeV/c, |y| < 0.9) = 1.46 ± 0.38 (stat.)$ _{-0.32}^{+0.26 } $(syst.)μb. The results are compared to QCD model predictions. The shape of theptandydistributions of b-quarks predicted by perturbative QCD model calculations are used to extrapolate the measured cross section to derive the$ \mathrm{b}\overline{\mathrm{b}} $pair total cross section and dσ/dyat mid-rapidity.