First observation of the decay Bc+→J/ψπ ⁺π ^-π ⁺

The decay Bc+→J/ψπ ⁺π ^-π ⁺ is observed for the first time, using 0.8fb ^-1 of pp collisions at √s=7TeV collected by the LHCb experiment. The ratio of branching fractions B(Bc+→J/ψπ ⁺π ^-π ⁺)/ B(Bc+→J/ψπ ⁺) is measured to be 2.41±0.30±0. 33, where the first uncertainty is statistical and the second is systematic. The result is in agreement with theoretical predictions.