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

Evidence for the decay mode X(3872) → ψ(2S) 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(2S) γ decay to that of the X(3872) → J/ψ γ decay is measured to be B(X(3872) → ψ(2S) 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 anti-D* molecular interpretation of the X(3872) state