Measurement of ψ(2S) Meson Production in pp Collisions at √s = 7 TeV

The differential cross-section for the inclusive production of ψ(2S) mesons in pp collisions at √s = 7 TeV has been measured with the LHCb detector. The data sample corresponds to an integrated luminosity of 36 pb^−1. The ψ(2S) mesons are reconstructed in the decay channels ψ(2S) → μ+ μ− and ψ(2S) → J/ψ π+ π−, with the J/ψ meson decaying into two muons. Results are presented both for promptly produced ψ(2S) mesons and for those originating from b-hadron decays. In the kinematic range pT(ψ(2S)) ≤ 16 GeV/c and 2 < y(ψ(2S)) ≤ 4.5 we measure σ_prompt(ψ(2S)) = 1.44 ± 0.01(stat) ± 0.12(syst)(+0.20)(−0.40)(pol) μb, σb(ψ(2S)) = 0.25 ± 0.01(stat) ± 0.02(syst) μb, where the last uncertainty on the prompt cross-section is due to the unknown ψ(2S) polarization. Recent QCD calculations are found to be in good agreement with our measurements. Combining the present result with the LHCb J/ψ measurements we determine the inclusive branching fraction B(b → ψ(2S) X) = (2.73 ± 0.06(stat) ± 0.16(syst) ± 0.24(BF))x10^−3, where the last uncertainty is due to the B(b → J/ψ X), B(J/ψ → μ+ μ−) and B(ψ(2S) → e+ e−) branching fraction uncertainties.