### Measurement of the Ratio of Branching Fractions $\cal{B}\mathrm{(B^{\pm} \rightarrow J/\psi \pi^{\pm})/\cal{B}\mathrm{(B^{\pm} \rightarrow J/\psi K^{\pm})}}$ at $\sqrt{\mathrm{s}}=7~\mathrm{TeV}$ with the LHCb DetectorMeasurement of the Ratio of Branching Fractions $\cal{B}\mathrm{(B^{\pm} \rightarrow J/\psi \pi^{\pm})/\cal{B}\mathrm{(B^{\pm} \rightarrow J/\psi K^{\pm})}}$ at $\sqrt{\mathrm{s}}=7~\mathrm{TeV}$ with the LHCb Detector

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 Source CERN Document Server File Format ZIP Date Created 2011-06-28 Language English
 Subject Domain (in DDC) Natural sciences & mathematics ♦ Physics ♦ Modern physics ♦ Technology ♦ Engineering & allied operations ♦ Applied physics Subject Keyword B physics ♦ Particle Physics - Experiment ♦ flavour physics Abstract The ratio of the branching fractions of the decays $\mathrm{B^{\pm} \rightarrow J/\psi \pi^{\pm}}$ and $\mathrm{B^{\pm} \rightarrow J/\psi K^{\pm}}$ has been measured with the LHCb detector in proton-proton collisions at a centre-of-mass energy of $\sqrt{\mathrm{s}}=7~\mathrm{TeV}$. The analysis is based on a data sample of 37~pb$^{-1}$ collected between April and November 2010 at the Large Hadron Collider. We observe $175 \pm 19$ $\mathrm{B^{\pm} \rightarrow J/\psi \pi^{\pm}}$ events and $5026 \pm 73$ $\mathrm{B^{\pm} \rightarrow J/\psi K^{\pm}}$ events. The ratio of the branching fractions is measured to be $\cal{B}\mathrm{(B^{\pm} \rightarrow J/\psi \pi^{\pm})}/\cal{B}\mathrm{(B^{\pm} \rightarrow J/\psi K^{\pm})} = \mathrm{(3.94 \pm 0.39(stat.) \pm 0.17(syst.)) \times 10^{-2}}$. Description Collaboration with: LHCb Learning Resource Type Notes Rights License Preprint: (License: CC-BY-4.0) Organization The LHCb Collaboration