Measurement of ψ(2S) meson production in pp collisions at √s =7 TeV

摘要

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/ψπ~+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) _(?0.40)~(+0.20) (pol) μb, σ_b(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))×10~(?3), where the last uncertainty is due to the B(b → J/ψX), B(J/ψ →μ~+μ~?) and B(ψ(2S)→e~+e~?) branching fraction uncertainties.