Quarkonium production in pp collisions at 7 TeV with the CMS experiment

Abstract

The production of J /{\psi} and {\Upsilon} mesons is studied in pp collisions at \surds = 7 TeV with the CMS experiment at the LHC. The J /{\psi} measurement is based on a dimuon sample corresponding to an integrated luminosity of 314 nb^{-1}. The J /{\psi} differential cross section is determined, as a function of the J/{\psi} transverse momentum, in three rapidity ranges. A fit to the decay length distribution is used to separate the prompt from the non-prompt (b hadron to J/{\psi}) component. Integrated over the J /{\psi} transverse momentum from 6.5 to 30 GeV/c and over rapidity in the range |y| < 2.4, the measured cross sections, times the dimuon decay branching fraction, are 70.9 \pm 2.1(stat.) \pm 3.0(syst.) \pm 7.8(lumi.) nb for prompt J /{\psi} mesons, assuming unpolarized production, and 26.0 \pm 1.4(stat.) \pm 1.6(syst.) \pm 2.9(lumi.) nb for J /{\psi} mesons from b-hadron decays. The {\Upsilon} measurement is based on a dimuon sample corresponding to an integrated luminosity 3.1 \pm 0.3 pb^{-1}. Integrated over the rapidity range |y| < 2, we find the product of the {\Upsilon}(1S) production cross section and branching fraction to dimuons to be 7.37 \pm 0.13(stat.)^{+0.61}_{-0.42}(syst.) \pm 0.81(lumi.) nb. This cross section is obtained assuming unpolarized {\Upsilon}(1S) production. If the {\Upsilon}(1S) production polarization is fully transverse or fully longitudinal, the cross section changes by about 20 %.