QCD factorization approach for rare ${\bar{B}}^0\to D^{\ast }\gamma$ decay

Abstract

We present the estimate of the branching ratio for the rare decay ${\bar{B}}^0\to D^{\ast }\gamma$. We use QCD factorization approach in order to compute the amplitude of the process. The calculation is carried out with the leading order accuracy. % Our consideration is based on the % factorization for the amplitude of the process which % has been derived with the leading order accuracy. The appearing non-perturbative matrix elements have been estimated using the large$-N_c$ limit and QCD sum rule approach. We obtained that $\mathcal{B}({\bar{B}}^0\to D^{\ast }\gamma )\simeq 1.52\times 10^{-7}$. Such value of the branching fraction is too small in order to be measured at present experiments.