Evidence for the decay X(3872) -> psi(2S)gamma

Abstract

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/ψγ decay is measured to be B(X(3872) → ψ(2S)γ) B(X(3872) → J/ψγ) = 2.46 ± 0.64 ± 0.29, where the first uncertainty is statistical and the second is systematic. The measured value agrees with expectations for a pure charmonium interpretation of the X(3872) state and a mixture of charmonium and molecular interpretations. However, it does not support a pure DD¯ ∗ molecular interpretation of the X(3872) state.