Revisit the radiative decays of J/Ψ and Ψ′ → γηc (γηc′)

With the new measurements of J/Psi and Psi ' -> gamma eta(c)(gamma eta(c)') from the CLEO and BES-III collaboration, we reinvestigate the intermediate meson loop (IML) contributions to these radiative decays in association with the quark model M1 transitions in an effective Lagrangian approach. It shows that the "unquenched'' effects due to the intermediate hadron loops can be better quantified by the new data for J/Psi -> gamma eta(c). Although the IML contributions are relatively small in J/Psi -> gamma eta(c), they play a crucial role in Psi' -> gamma eta(c)(gamma eta(c)'). A prediction for the IML contributions to Psi(3770) -> gamma eta(c)(gamma eta(c)') is made. Such unquenched effects allow us to reach a coherent description of those three radiative transitions, and gain some insights into the underlying dynamics.