Observation of the decay Bc+→ψ(2S)π+

The decay Bc+→ψ(2S)π+ with ψ(2S)→μ+μ- is observed with a significance of 5.2σ using pp collision data corresponding to an integrated luminosity of 1.0  fb-1 collected by the LHCb experiment. The branching fraction of Bc+→ψ(2S)π+ decays relative to that of the Bc+→J/ψπ+ mode is measured to be B(Bc+→ψ(2S)π+)/B(Bc+→J/ψπ+)=0.250±0.068(stat)±0.014(syst)±0.006(B). The last term is the uncertainty on the ratio B(ψ(2S)→μ+μ-)/B(J/ψ→μ+μ-).