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First observation of the decay $B_{c}^{+}\to J/\psi K^+$

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Abstract

The decay $B_c^+\to J/\psi K^+$ is observed for the first time using a data sample, corresponding to an integrated luminosity of 1.0 ${\,fb}^{-1}$, collected by the LHCb experiment in $pp$ collisions at a centre-of-mass energy of $7\mathrm{\,TeV}$. A yield of $46\pm12$ events is reported, with a significance of 5.0 standard deviations. The ratio of the branching fraction of $B_c^+\to J/\psi K^+$ to that of $B_c^+\to J/\psi\pi^+$ is measured to be $0.069\pm0.019\pm0.005$, where the first uncertainty is statistical and the second is systematic.

Figures and captions

Diagram for a $ B _ c ^+ \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \pi ^+ ( K ^+ )$ decay.

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Mass distributions of $ B _ c ^+$ candidates in four $\mathrm{DLL}_{ K \pi }$ bins and the superimposed fit results. The solid shaded area (red) represents the $ B _ c ^+ \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K ^+ $ signal and the hatched area (blue) the $ B _ c ^+ \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \pi ^+ $ signal. The dot-dashed line (blue) indicates the partially reconstructed background and the dotted (red) the combinatorial background. The solid line (black) represents the sum of the above components and the points with error bars (black) show the data. The labels $(a)$, $(b)$, $(c)$ and $(d)$ correspond to $\mathrm{DLL}_{ K \pi } <-5$, $-5<\mathrm{DLL}_{ K \pi } <0$, $0<\mathrm{DLL}_{ K \pi } <5$ and $\mathrm{DLL}_{ K \pi } >5$ for the bachelor track, respectively.

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Animated gif made out of all figures.

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Tables and captions

Relative systematic uncertainties on the ratio of branching fractions.

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tex code
Table_1.pdf

Created on 09 December 2018.Citation count from INSPIRE on 18 December 2018.