Observation of the ${\Lambda }_b^0\to {\Lambda }_c^{+}{K}^{+}{K}^{-}{\pi }^{-}$ decay

The ${\Lambda }_b^0\to {\Lambda }_c^{+}{K}^{+}{K}^{-}{\pi }^{-}$ 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 $\mathrm{T}\mathrm{e}\mathrm{V}$ collected by the $LHCb$ detector, corresponding to an integrated luminosity of $3{\mathrm{f}\mathrm{b}}^{-1}$. The ratio of branching fractions between the $\varLambda^0_b \to \varLambda^+c K^+ K^- \pi^-$andthe$\varLambda^{0}{b}\to\varLambda^{+}{c}D^{-}{s}$ 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 ${\Lambda }_c^{+}{K}^{+}$ system is found, consistent with no open-charm pentaquark signature.