Abstract
The differential cross-section for the inclusive production of ψ(2S) mesons in pp collisions at sqrt{s}=7 mbox{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 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 where the last uncertainty is due to the mathcal{B}(b rightarrow J/psi X), mathcal{B}(J/psirightarrowmu^{+} mu^{-}) and mathcal{B}(psi(2S) rightarrow e^{+} e^{-}) branching fraction uncertainties.
Highlights
Since its discovery, heavy quarkonium has been one of the most important test laboratories for the development e-mail: decapua.stefano@gmail.com of QCD at the border between the perturbative and nonperturbative regimes, resulting in the formulation of the nonrelativistic QCD (NRQCD) factorisation formalism [1, 2]
Prompt production studies carried out at the Tevatron collider in the early 1990s [3] made clear that NRQCD calculations, based on the leading-order (LO) colour-singlet model (CSM), failed to describe the absolute value and the transverse momentum dependence of the charmonium production cross-section and polarization data
To assess possible systematic differences in the acceptance between data and simulation for the J /ψπ+π − mode, we have studied the dipion mass distribution
Summary
Heavy quarkonium is produced from b-hadron decays. It can be distinguished from promptly produced quarkonium exploiting its finite decay time. To allow a comparison with theory, promptly produced quarkonia should be separated from those coming from b-hadron decays and from those cascading from higher mass states (feed-down). The latter contribution strongly affects J /ψ production and complicates the interpretation of prompt J /ψ data. Ψ(2S) charmonium has no appreciable feed-down from higher mass states and the results can be directly compared with the theoretical predictions, making it an ideal laboratory for QCD studies. [8] for the J /ψ production studies; in particular, the separation between promptly produced ψ(2S) and those originating from b-hadron decays is based on the reconstructed decay vertex information. The production of ψ(2S) meson at the LHC has been studied at the CMS experiment [9]
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