Radiative decay of the X(3872) state as a mixture of molecule and charmonium

We use QCD sum rules to calculate the width of the radiative decay of the meson X(3872), assumed to be a mixture between charmonium and exotic molecular [cq¯][qc¯] states with JPC=1++. We find that in a small range for the values of the mixing angle, 5°⩽θ⩽13°, we get the branching ratio Γ(X→J/ψγ)/Γ(X→J/ψπ+π−)=0.19±0.13, which is in agreement, with the experimental value. This result is compatible with the analysis of the mass and decay width of the mode J/ψ(nπ) performed in the same approach.