Electromagnetic decays of vector mesons as derived from QCD sum rules
  We apply the method of QCD sum rules in the presence of external electromagnetic fields $F_{\mu\nu}$ to the problem of the electromagnetic decays of various vector mesons, such as $\rho\to\pi\gamma$, $K^\ast\to K\gamma$ and $\eta'\to\rho\gamma$. The induced condensates obtained previously from the study of baryon magnetic moments are adopted, thereby ensuring the parameter-free nature of the present calculation. Further consistency is reinforced by invoking various QCD sum rules for the meson masses. The numerical results on the various radiative decays agree very well with the experimental data. 
Shi-lin Zhu(1,2), W.-Y.P. Hwang (3) and Ze-sen Yang(1) ((1) Physics   Department, Peking University, (2) Institute of Theore...