Radiative Leptonic B Decays in the Light Front Model

Abstract

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