B0→D0/emph>+γdecay as a probe for short-distance QCD corrections

We argue that, barring a large gqq¯ component in the $B^0$ or $D^{0\mathrm{*}}$ meson wave functions, the $B^0$→$D^{0\mathrm{*}}$+γ decay will be highly suppressed by QCD short-distance corrections. This decay proceeds mainly through flavor annihilation, and ‘‘color thaw’’ by gluon emission from the initial quark legs is not expected to be operative here. Thus the relevant color suppression factor $A_{\mathrm{QCD}=(2\mathrm{}{C}_{+}\mathrm{-}{C}_{\mathrm{-}}{)}^2\lesssim 0.1}$ should be in place. We calculate the decay rate in a nonrelativistic approximation and obtain the estimate B($B^0$→$D^{0\mathrm{*}}$+γ)≊2×${10}^{\mathrm{-}6}$. .AE