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

The Λb0→Λc+K+K−π− decay is observed for the first time using a data sample of proton-proton collisions at centre-of-mass energies of s=7 and 8TeV collected by the LHCb detector, corresponding to an integrated luminosity of 3fb−1 . The ratio of branching fractions between the Λb0→Λc+K+K−π− and the Λb0→Λc+Ds− decays is measured to be B(Λb0→Λc+K+K−π−)B(Λb0→Λc+Ds−)=(9.26±0.29±0.46±0.26)×10−2, where the first uncertainty is statistical, the second systematic and the third is due to the knowledge of the Ds−→K+K−π− branching fraction. No structure on the invariant mass distribution of the Λc+K+ system is found, consistent with no open-charm pentaquark signature.