3,297 research outputs found

    Multiplicity dependence of σψ(2S)/σJ/ψ\sigma_{\psi(2S)}/\sigma_{J/\psi} in pppp collisions at s=13\sqrt{s}=13 TeV

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    International audienceThe ratio of production cross-sections of ψ(2S)\psi(2S) over J/ψJ/\psi mesons as a function of charged-particle multiplicity in proton-proton collisions at a centre-of-mass energy s=13\sqrt{s}=13 TeV is measured with a data sample collected by the LHCb detector, corresponding to an integrated luminosity of 658 pb1^{-1}. The ratio is measured for both prompt and non-prompt ψ(2S)\psi(2S) and J/ψJ/\psi mesons. When there is an overlap between the rapidity ranges over which multiplicity and charmonia production are measured, a multiplicity-dependent modification of the ratio is observed for prompt mesons. No significant multiplicity dependence is found when the ranges do not overlap. For non-prompt production, the ψ(2S)toJ/ψ\psi(2S)-to-J/\psi production ratio is roughly independent of multiplicity irrespective of the rapidity range over which the multiplicity is measured. The results are compared to predictions of the co-mover model and agree well except in the low multiplicity region. The ratio of production cross-sections of ψ(2S)\psi(2S) over J/ψJ/\psi mesons are cross-checked with other measurements in di-lepton channels and found to be compatible

    Measurement of multidifferential cross sections for dijet production in proton-proton collisions at s\sqrt{s} = 13 TeV

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    International audienceA measurement of the dijet production cross section is reported based on proton-proton collision data collected in 2016 at s\sqrt{s} = 13 TeV by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of up to 36.3 fb1^{-1}. Jets are reconstructed with the anti-kTk_\mathrm{T} algorithm for distance parameters of RR = 0.4 and 0.8. Cross sections are measured double-differentially (2D) as a function of the largest absolute rapidity ymax\lvert y_\text{max}\rvert of the two jets with the highest transverse momenta pTp_\mathrm{T} and their invariant mass m1,2m_{1,2}, and triple-differentially (3D) as a function of the rapidity separation yy^*, the total boost yby_\mathrm{b}, and either m1,2m_{1,2} or the average pTp_\mathrm{T} of the two jets. The cross sections are unfolded to correct for detector effects and are compared with fixed-order calculations derived at next-to-next-to-leading order in perturbative quantum chromodynamics. The impact of the measurements on the parton distribution functions and the strong coupling constant at the mass of the Z boson is investigated, yielding a value of αS\alpha_\mathrm{S} = 0.1179 ±\pm 0.0019

    Search for Bc+π+μ+μB_c^+\to\pi^+\mu^+\mu^- decays and measurement of the branching fraction ratio B(Bc+ψ(2S)π+)/B(Bc+J/ψπ+){\cal B}(B_c^+\to\psi(2S)\pi^+)/{\cal B}(B_c^+\to J/\psi \pi^+)