Measurement of quarkonium production at forward rapidity in pp collisions at √s=7 TeV

The inclusive production cross sections at forward rapidity of J/ψ, ψ(2S), Y(1S) and Y(2S) are measured in pp collisions at √s = 7 TeV with the ALICE detector at the LHC. The analysis is based on a data sample corresponding to an integrated luminosity of 1.35 pb-1. Quarkonia are reconstructed in the dimuon-decay channel and the signal yields are evaluated by fitting the μ+μ- invariant mass distributions. The differential production cross sections are measured as a function of the transverse momentum pT and rapidity y, over the ranges 0 < pT < 20 GeV/c for J/ψ, 0 < pT < 12 GeV/c for all other resonances and for 2.5 < y < 4. The measured cross sections integrated over pT and y, and assuming unpolarized quarkonia, are: σJ/ψ = 6.69 ± 0.04 ± 0.63 μb, σψ(2S) = 1.13 ± 0.07 ± 0.19 μb, σY(1S) = 54.2 ± 5.0 ± 6.7 nb and σY(2S) = 18.4 ± 3.7 ± 2.9 nb,where the first uncertainty is statistical and the second one is systematic. The results are compared to measurements performed by other LHC experiments and to theoretical models.