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    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

    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^+)