Effective Lagrangian for Heavy and Light Mesons: Radiative B Decays

We make use of the information obtained from semileptonic decays of $B$ and $D$ mesons, within an effective lagrangian description based on heavy quark theory and on chiral expansion, to study the radiative decays $B \to K^\star \gamma$ and $B_S \to \phi\gamma$, and the pair conversion processes $B \to K e^+e^-$ and $B \to K^\star e^+e^-$. We discuss with care the required extrapolations from zero recoils. We obtain a BR($B\to K^\star\gamma$) between $1.3\times 10^{-5}$ and $4.1\times 10^{-5}$ and BR($B_s \to\phi\gamma$) between $1.4\times 10^{-5}$ and $4.5\times 10^{-5}$, with errors mainly arising from the present uncertainty in the Kobayashi-Maskawa element $|V_{ts}|$. For the pair conversion processes we study in particular the lepton effective mass distributions whose measurements would allow for an understanding both long distance and short distance contributions to such processes.