B¯→K*γfromD→K*l¯ν

Abstract

The $\overline{B}\ensuremath{\rightarrow}{K}^{*}\ensuremath{\gamma}$ branching fraction is predicted using heavy quark spin symmetry at large recoil to relate the tensor and (axial-)vector form factors, using heavy quark flavor symmetry to relate the B decay form factors to the measured $\stackrel{\ensuremath{\rightarrow}}{D}{K}^{*}\overline{l}\ensuremath{\nu}$ form factors, and extrapolating the semileptonic B decay form factors to large recoil assuming nearest pole dominance. This prediction agrees with data surprisingly well, and we comment on its implications for the extraction of $|{V}_{\mathrm{ub}}|$ from $\overline{B}\ensuremath{\rightarrow}\ensuremath{\rho}l\overline{\ensuremath{\nu}}.$