Leptonic Constant from B Meson Radiative Decay

We propose a method to determine the leptonic decay constant $f_{B^*}$ in the infinite heavy quark mass limit from the analysis of the radiative decay mode $B^- \to \ell^- {\bar \nu}_\ell \gamma$. The method relies on HQET symmetries and on experimental data from $D^{*0} \to D^0 \gamma$.