Evidence for the Decay X(3872) → ψ(2S)γ

Abstract Evidence for the decay mode X ( 3872 ) → ψ ( 2 S ) γ in B + → X ( 3872 ) K + decays is found with a significance of 4.4 standard deviations. The analysis is based on a data sample of proton–proton collisions, corresponding to an integrated luminosity of 3 fb −1 , collected with the LHCb detector, at centre-of-mass energies of 7 and 8 TeV. The ratio of the branching fraction of the X ( 3872 ) → ψ ( 2 S ) γ decay to that of the X ( 3872 ) → J / ψ γ decay is measured to be B ( X ( 3872 ) → ψ ( 2 S ) γ ) B ( X ( 3872 ) → J / ψ γ ) = 2.46 ± 0.64 ± 0.29 , where the first uncertainty is statistical and the second is systematic. The measured value does not support a pure D D ¯ ⁎ molecular interpretation of the X ( 3872 ) state.