Effects of heavy meson loops on heavy quarkonium radiative transitions.

Radiative transitions between charmonium states offer an insight into the internal structure of heavy quark bound states within QCD. In this work, we systematically investigate the coupled-channel effects of intermediate charmed mesons to charmonium radiative transitions utilizing an effective Lagrangian approach. Our results show that the coupled-channel effects of these decays under the open charm thresholds are relatively weak, while the coupled-channel effects of the excited P-wave states close to the charmed pairs thresholds are relatively important. [ABSTRACT FROM AUTHOR]