Leptonic Constant from B Meson Radiative Decay

Abstract

We propose a method to determine the leptonic decay constant $f_{B^{\ast }}$ 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 $D^{\ast 0}\to D^0\gamma$.

Comments: LaTex, 14 pages, 2 uuencoded figures. This version will appear on Physics Letters B