Radiative decay of the X(3872) as a mixed molecule-charmonium state in QCD Sum Rules

Abstract

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 $[c\bar{q}][q\bar{c}]$ states with $J^{PC}=1^{++}$. We find that in a small range for the values of the mixing angle, $5^0\le \theta \le 13^0$, we get the branching ratio $\Gamma (X\to J/\psi \gamma )/\Gamma (X\to J/\psi {\pi }^{+}{\pi }^{-})=0.19\pm 0.13$, which is in agreement, with the experimental value. This result is compatible with the analysis of the mass and decay width of the mode $J/\psi (n\pi )$ performed in the same approach.

Comments: 7 pages, 9 figures; revised version accepted for publication in Phys. Rev. D