Evidence for the decay $X(3872)\rightarrowψ(2S)γ$

Abstract

Evidence for the decay mode $X(3872)\rightarrowψ(2S)γ$ in $B^+\rightarrow X(3872)K^+$ 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 3fb$^{-1}$ collected with the LHCb detector, at centre-of-mass energies of 7 and 8TeV. The ratio of the branching fraction of the $X(3872)\toψ(2S)γ$ decay to that of the $X(3872)\rightarrow J/ψγ$ decay is measured to be $$ \frac{Br(X(3872)\rightarrowψ(2S)γ)}{Br(X(3872)\rightarrow J/ψγ)} = 2.46\pm0.64\pm0.29, %\pm0.06,$$ 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 $D\bar{D}^{*}$ molecular interpretation of the $X(3872)$state.

19 pages, 4 figures