1,084 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

    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^+)

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    International audienceThe first search for nonresonant Bc+π+μ+μB_c^+\to\pi^+\mu^+\mu^- decays is reported. The analysis uses proton-proton collision data collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9 fb1^{-1}. No evidence for an excess of signal events over background is observed and an upper limit is set on the branching fraction ratio B(Bc+π+μ+μ)/B(Bc+J/ψπ+)<2.1×104{\cal B}(B_c^+\to\pi^+\mu^+\mu^-)/{\cal B}(B_c^+\to J/\psi \pi^+) < 2.1\times 10^{-4} at 90%90\% confidence level. Additionally, an updated measurement of the ratio of the Bc+ψ(2S)π+B_c^+\to\psi(2S)\pi^+ and Bc+J/ψπ+B_c^+\to J/\psi \pi^+ branching fractions is reported. The 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^+) is measured to be 0.254±0.018±0.003±0.0050.254\pm 0.018 \pm 0.003 \pm 0.005, where the first uncertainty is statistical, the second systematic, and the third is due to the uncertainties on the branching fractions of the leptonic J/ψJ/\psi and ψ(2S)\psi(2S) decays. This measurement is the most precise to date and is consistent with previous LHCb results

    Observation of the Bc+J/ψπ+π0B_c^+ \to J/\psi \pi^+ \pi^0 decay