Understanding the radiative decays of vector charmonia to light pseudoscalar mesons

We show that the newly measured branching ratios of vector charmonia (J/psi, psi' and psi(3770)) into gamma P, where P stands for light pseudoscalar mesons pi(0), eta and eta', can be well understood in the framework of vector meson dominance (VMD) in association with the eta(c)-eta(eta') mixings due to the axial gluonic anomaly. These two mechanisms behave differently in J/psi and psi' -> gamma P. A coherent understanding of the branching ratio patterns observed in J/psi(psi') -> gamma P can be achieved by self-consistently including those transition mechanisms at hadronic level. The branching ratios for psi (3770) -> gamma P are predicted to be rather small. (C) 2011 Elsevier B.V. All rights reserved.