Study of weak radiative decays of $D^0\to V \gamma$

The weak radiative decay of $D^0\to V\gamma$ with $V=\bar{K}^0$, and $\phi$, $\rho^0$, and $\omega$, is systematically studied in the vector meson dominance (VMD) model. It allows us to distinguish the short-distance mechanisms which can be described by the tree-level transitions in the non-relativistic constituent quark model, and the long-distance mechanisms which are related to the final-state interactions (FSIs). We find that the FSI effects play a crucial role in $D^0\to V\gamma$ and the SU(3) flavor symmetry can provide a natural constraint on the relative phase between the short and long-distance transition amplitudes. Our analysis suggests that the $D$ meson weak radiative decays can serve as a good case for investigating the non-perturbative QCD mechanisms at the charm quark mass region.