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)×B(ϒ (1S)→μ ⁺ μ ⁻) = 2.29 ± 0.01 ± 0.10^+0.19 _−0.37 nb, σ(pp→ϒ (2S)X)×B(ϒ (2S)→μ ⁺ μ ⁻) = 0.562±0.007±0.023^+0.048 _−0.092 nb, σ(pp→ϒ (3S)X)×B(ϒ (3S)→μ ⁺ μ ⁻) = 0.283±0.005±0.012^+0.025 _−0.048 nb, where the first uncertainty is statistical, the second systematic and the third is due to the unknown polarisation of the three ϒ states.