Factorization inB→Vγdecays

The factorization properties of the radiative decays $B\to V\gamma$ are analyzed at leading order in $1/m_b$ using the soft-collinear effective theory. It is shown that the decay amplitudes can be expressed in terms of a $B\to V$ form factor evaluated at $q^2=0$, light-cone distribution amplitudes of the $B$ and $V$ mesons, and calculable hard-scattering kernels. The renormalization-group equations in the effective theory are solved to resum perturbative logarithms of the different scales in the decay process. Phenomenological implications for the $B\to K^{*}\gamma$ branching ratio, isospin asymmetry, and $CP$ asymmetries are discussed, with particular emphasis on possible effects from physics beyond the standard model.