Abstract
The production of $J/\psi$ mesons in proton-proton collisions at a centre-of-mass energy of $\sqrt{s}=13$ TeV is studied with the \lhcb detector. Cross-section measurements are performed as a function of the transverse momentum $p_\mathrm{T}$ and the rapidity $y$ of the $J/\psi$ meson in the region $p_\mathrm{T}<14\mathrm{GeV}/c$ and $2.0<y<4.5$, for both prompt $J/\psi$ mesons and $J/\psi$ mesons from $b$-hadron decays. The production cross-sections integrated over the kinematic coverage are $15.03\pm 0.03\pm 0.94$ $\mu$b for prompt $J/\psi$ and $2.25\pm 0.01\pm 0.14$ $\mu$b for $J/\psi$ from $b$-hadron decays, assuming zero polarization of the $J/\psi$ meson. The first uncertainties are statistical and the second systematic. The cross-section reported for $J/\psi$ mesons from $b$-hadron decays is used to extrapolate to a total $b\bar{b}$ cross-section. The ratios of the cross-sections with respect to $\sqrt{s}=8$ TeV are also determined.
Highlights
√ of the cross-sections with respect to s = 8 TeV are determined
The J/ψ polarisation was √measured by the ALICE [28], CMS [29] and LHCb [30] collaborations in pp collisions at s = 7 TeV
√ This paper reports J/ψ cross-section measurements in pp collisions at s = TeV in the J/ψ kinematic range pT < GeV/c and 2.0 < y < 4.5, using J/ψ decaying to μ+μ− final states
Summary
The online event selection consists of a hardware stage, based on information from the calorimeter and muon systems, followed by a software stage, which performs J/ψ candidate reconstruction. In the first stage of the software trigger, two muon tracks with pT > 500 MeV/c are required to form a J/ψ candidate with invariant mass M (μ+μ−) > 2.7 GeV/c2. J/ψ candidates with good vertex fit quality and invariant mass within 150 MeV/c2 of the known value [43] are selected. This analysis benefits from a new scheme for the LHCb software trigger introduced for LHC Run 2. To further select good J/ψ candidates, the uncertainty on tz, which is propagated from the uncertainties provided by the track reconstruction, is required to be less than 0.3 ps
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