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.