Abstract
AbstractA measurement of theJ/ψandψ(2S) production cross sections in pp collisions at$ \sqrt {s} = 7{\text{TeV}} $with the CMS experiment at the LHC is presented. The data sample corresponds to an integrated luminosity of 37 pb−1. Using a fit to the invariant mass and decay length distributions, production cross sections have been measured separately for prompt and non-prompt charmonium states, as a function of the meson transverse momentum in several rapidity ranges and integrated in the kinematical regions considered in this study. In addition, cross sections restricted to the acceptance of the CMS detector are given, which are not affected by the polarization of the charmonium states. The ratio of the differential production cross sections of the two states, where systematic uncertainties largely cancel, is also determined. The branching fraction of the inclusive B →ψ(2S)Xdecay is extracted from the ratio of the non-prompt cross sections to be:$ \mathcal{B}\left( {{\text{B}} \to \psi \left( {\text{2S}} \right)X} \right) = \left( {{3}.0{8}\pm 0.{12}\left( {{\text{stat}}. + {\text{syst}}.} \right)\pm 0.{13}\left( {{\text{theor}}.} \right)\pm 0.{42}\left( {{\mathcal{B}_{\text{PDG}}}} \right)} \right) \times {1}{0^{{ - {3}}}}. $
Highlights
The present analysis extends the Compact Muon Solenoid (CMS) result with a larger amount of statistically independent data and complements it by providing a measurement of the ψ(2S) production cross section, as well as the ratio of the two cross sections
They are compared with theoretical predictions from nonrelativistic QCD (NRQCD) [3] and from fixed-order next-to-leading-log (FONLL) [5, 6] for the prompt and non-prompt cases, respectively
Since the polarization effects are large compared to the measurement uncertainties, cross section values are reported that are restricted to the CMS muon acceptance region, to allow future measurements of the J/ψ and ψ(2S) polarization to be exploited
Summary
The J/ψ double-differential cross section is given by: d2σ (J/ψ) · B(J/ψ → μ+μ−) = NJc/oψrr(pT, |y|). Where L dt is the integrated luminosity, ∆pT and ∆y are the pT and y bin widths, B(J/ψ → μ+μ−) is the decay branching fraction of the J/ψ into two muons, and NJc/oψrr(pT, |y|) is the corrected J/ψ yield in a given (pT, |y|) bin. J/ψ yields are corrected for acceptance (A) and efficiency ( ), and NJc/oψrr = NJ/ψ ·. Because of the large difference in the branching fractions to dimuons of the two states, the measured ψ(2S) yield is much smaller than the J/ψ yield For this reason, different binnings are used for the differential cross sections in pT and |y|. 6.5 < pT < 30.0 GeV/c for |y| < 1.2 5.5 < pT < 30.0 GeV/c for 1.2 < |y| < 2.4
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