Observation of the decay $B_c^+ \rightarrow J/\psi K^+ K^- \pi^+$

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The decay $B_c\rightarrow J/\psi K^+ K^- \pi^+$ is observed for the first time, using proton-proton collisions collected with the LHCb detector corresponding to an integrated luminosity of 3fb$^{-1}$. A signal yield of $78\pm14$ decays is reported with a significance of 6.2 standard deviations. The ratio of the branching fraction of $\B_c \rightarrow J/\psi K^+ K^- \pi^+$ decays to that of $B_c \rightarrow J/\psi \pi^+$ decays is measured to be $0.53\pm 0.10\pm0.05$, where the first uncertainty is statistical and the second is systematic.

Figures and captions

Mass distribution for selected (a) $ B _ c ^+ \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K ^+ K ^- \pi ^+ $ and (b) $ B _ c ^+ \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \pi ^+ $ candidates. The result of the fit described in the text is superimposed (solid line) together with the background component (dashed line).

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Background-subtracted invariant mass distributions for (a) $ K ^- \pi ^+ $, (b) $ K ^+ K ^- $, (c) $ K ^+ K ^- \pi ^+ $, (d) $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K ^+ K ^- $, (e) $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K ^- \pi ^+ $ and (f) $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K ^+ $ in $ B _ c ^+ \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K ^+ K ^- \pi ^+ $ decay. The (red) full line in the $ K ^- \pi ^+ $ mass distribution (a) is composed of a resonant $\overline{ K }^{*0}$ contribution and a non-resonant component indicated by the dashed line. The (blue) full line in (b)--(f) shows the predictions of the model [20] used in the simulation. The regions $\pm 18 {\mathrm{ Me V /}c^2} $ around the $ D ^+_ s $ mass and $\pm 51 {\mathrm{ Me V /}c^2} $ around the $ B ^0_ s $ mass are excluded from the analysis and are indicated by the shaded areas on (c) and (d), respectively.

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Animated gif made out of all figures.


Tables and captions

Parameters of the signal function of the fit to the $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K ^+ K ^- \pi ^+ $ mass distribution. Uncertainties are statistical only.

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Relative systematic uncertainties for the ratio of branching fractions of $ B _ c ^+ \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K ^+ K ^- \pi ^+ $ and $ B _ c ^+ \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \pi ^+ $. The total uncertainty is the quadratic sum of the individual components.

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Created on 19 February 2021.