Observation of the decay -> J/psi K (+) K (-) pi (+)

The decay -> J/psi K (+) K (-) pi (+) is observed for the first time, using protonproton collisions collected with the LHCb detector corresponding to an integrated luminosity of 3 fb(-1). A signal yield of 78 +/- 14 decays is reported with a significance of 6.2 standard deviations. The ratio of the branching fraction of -> J/psi K (+) K (-) pi (+) decays to that of -> J/psi IEuro (+) decays is measured to be 0.53 +/- 0.10 +/- 0.05, where the first uncertainty is statistical and the second is systematic.