Radiative Leptonic B Decays in the Light Front Model

Within the light front framework, we calculate the form factors for $B\to \gamma$ transitions directly in the entire physical range of momentum transfer. Using these form factors, we study the radiative decays of $B\to l\nu_l\gamma$and$B_{s(d)}\to\nu\bar{\nu}\gamma$. We show that the decay rates of $B\to l{\nu }_l\gamma (l=e,\mu )$ and $B\to \nu \bar{\nu }\gamma$ are larger than that of the corresponding purely leptonic modes. Explicitly, in the standard model, we find that the branching ratios of $B\to \mu {\nu }_{\mu }\gamma$ and $B_s\to \nu \bar{\nu }\gamma$ are $3.7\times {10}^{-6}$ and $5.0\times {10}^{-8}$, in contrast with $3\times {10}^{-7}$ and 0 for $B\to \mu {\nu }_{\mu }$ and $B\to \nu \bar{\nu }$, respectively.