B^+ --> D^{*+}_s gamma and B^+ --> D^{*+} gamma as Probes of V_{ub}

Abstract

The decays B^+ --> D^{*+}_s gamma and B^+ --> D^{*+} gamma can be used for an extraction of |V_{ub}|. When the b and c quarks are nearly degenerate the rate for these modes can be determined in terms of other observed rates, namely B\bar{B} mixing and D^* --> D gamma decay. To this end we introduce a novel application of heavy quark and flavor symmetries. Although somewhat unrealistic, this limit provides us with a first estimate of these rates.