Measurement of ϒ Production in pp Collisions at √s = 7 TeV

The production of ϒ(1S), ϒ(2S) and ϒ(3S) mesons in proton-proton collisions at the centre-of-mass energy of √s = 7 TeV is studied with the LHCb detector. The analysis is based on a data sample of 25 pb^−1 collected at the Large Hadron Collider. The ϒ mesons are reconstructed in the decay mode ϒ → μ+ μ− and the signal yields are extracted from a fit to the μ+ μ− invariant mass distributions. The differential production cross-sections times dimuon branching fractions are measured as a function of the ϒ transverse momentum p_T and rapidity y, over the range p_T < 15 GeV/c and 2.0 < y < 4.5. The cross-sections times branching fractions, integrated over these kinematic ranges, are measured to be σ(pp → ϒ(1S) X) x B(ϒ(1S) → μ+ μ−) = 2.29 ± 0.01 ± 0.10(−0.37)(+0.19) nb, σ(pp → ϒ(2S) X) x B(ϒ(2S) → μ+ μ−) = 0.562 ± 0.007 ± 0.023(−0.092)(+0.048) nb, σ(pp → ϒ(3S) X) x B(ϒ(3S) → μ+ μ−) = 0.283 ± 0.005 ± 0.012(−0.048)(+0.025) nb, where the first uncertainty is statistical, the second systematic and the third is due to the unknown polarisation of the three ϒ states.