# 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. Fig1.pdf [22 KiB] HiDef png [97 KiB] Thumbnail [32 KiB] *.C file 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. Fig2a.pdf [36 KiB] HiDef png [287 KiB] Thumbnail [234 KiB] *.C file Fig2b.pdf [33 KiB] HiDef png [299 KiB] Thumbnail [231 KiB] *.C file 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). Fig3.pdf [39 KiB] HiDef png [283 KiB] Thumbnail [205 KiB] *.C file 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. Fig4a.pdf [21 KiB] HiDef png [198 KiB] Thumbnail [169 KiB] *.C file Fig4b.pdf [17 KiB] HiDef png [160 KiB] Thumbnail [138 KiB] *.C file Fig4c.pdf [20 KiB] HiDef png [216 KiB] Thumbnail [190 KiB] *.C file Animated gif made out of all figures. PAPER-2020-028.gif Thumbnail

## Tables and captions

 Summary of systematic uncertainties on the ratio of branching fractions. Table_1.pdf [74 KiB] HiDef png [88 KiB] Thumbnail [39 KiB] tex code

Created on 06 March 2021.