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Observation of the $\varLambda^{0}_{b}\to\varLambda^{+}_{c}K^{+}K^{-}\pi^{-}$ decay

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Abstract

The $\varLambda^0_b \to \varLambda^+_c K^+ K^- \pi^-$ decay is observed for the first time using a data sample of proton-proton collisions at centre-of-mass energies of $\sqrt{s}=7$ and 8 $\rm{TeV}$ collected by the $ LHCb$ detector, corresponding to an integrated luminosity of $3{\rm{fb}^{-1}}$. The ratio of branching fractions between the $\varLambda^0_b \to \varLambda^+_c K^+ K^- \pi^-$ and the $\varLambda^{0}_{b}\to\varLambda^{+}_{c}D^{-}_{s}$ decays is measured to be \begin{equation*} \frac{\mathcal{B} ( \varLambda^0_b \to \varLambda^+_c K^+ K^- \pi^-) } {\mathcal{B} ( \varLambda^0_b \to \varLambda^+_c D^-_s)} = (9.26 \pm 0.29 \pm 0.46 \pm 0.26)\times10^{-2}, \end{equation*} where the first uncertainty is statistical, the second systematic and the third is due to the knowledge of the $D^-_s \to K^+ K^- \pi^-$ branching fraction. No structure on the invariant mass distribution of the $\varLambda^+_c K^+$ system is found, consistent with no open-charm pentaquark signature.

Figures and captions

Feynman diagram of the leading contribution to the $\Lambda ^0_ b \rightarrow \Lambda ^+_ c K ^+ K ^- \pi ^- $ signal decay.

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Invariant mass distribution of (a) $\Lambda ^0_ b \rightarrow \Lambda ^+_ c K ^+ K ^- \pi ^- $ and (b) $\Lambda ^0_ b \rightarrow \Lambda ^+_ c D ^-_ s $ candidates. Fit projections are overlaid as a blue solid line. For (a), the red solid line represents the signal component, the blue dashed line is the background due to random combinations, and the violet dotted line is the contribution from $\Lambda ^0_ b \rightarrow \Sigma _ c ^+ K ^+ K ^- \pi ^- $ decays. For (b), the red solid line is the normalization channel component, the violet dotted line is the $\Lambda ^0_ b \rightarrow \Lambda ^+_ c D ^{*-}_ s $ background, the green dashed-dotted line is the contribution from $\Lambda ^0_ b \rightarrow \Lambda ^+_ c K ^+ K ^- \pi ^- $ decays, and the blue dashed line represents combinatorial background.

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Invariant mass distributions of $\Lambda ^+_ c $ $ K ^+$ candidates in the $\Lambda ^0_ b \rightarrow \Lambda ^+_ c K ^+ K ^- \pi ^- $ signal channel for the simulation (red line) and the background-subtracted data (blue points with error bars).

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Invariant mass distributions of (a) the $\Lambda ^+_ c $ $\pi ^-$ , (b) $ K ^+$ $\pi ^-$ , and (c) $ K ^+$ $ K ^-$ $\pi ^-$ systems in the $\Lambda ^0_ b \rightarrow \Lambda ^+_ c K ^+ K ^- \pi ^- $ signal channel, for the background-subtracted data. The red dashed vertical lines indicate the veto mass intervals for $\overline{ D } {}^0 $ mesons in the $ K ^+ \pi ^- $ distribution, and $ D ^-_ s $ in the $ K ^+ K ^- \pi ^- $ distribution.

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Animated gif made out of all figures.

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Tables and captions

Summary of systematic uncertainties on the ratio of branching fractions.

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Table_1.pdf

Created on 06 March 2021.