Subleading power corrections to the B →γ l ν decay in the perturbative QCD approach

The leptonic radiative decay B →γ ℓν is of great importance in the determination of B -meson wave functions, and evaluating the form factors F_{V ,A} is the essential problem on the study of this channel. We compute the next-to-leading power corrections to the form factors within the framework of PQCD approach, including the power suppressed hard kernel, the contribution from a complete set of three-particle B -meson wave functions up to twist-4 and two-particle off light-cone wave functions, the 1 /m_b corrections in heavy quark effective theory (HQET), and the contribution from hadronic structure of photon. In spite of large theoretical uncertainties, the overall power suppressed contributions decreases about 50% of the leading power result. The λ_B dependence of the integrated branching ratio is reduced after including the subleading power contributions, thus the power corrections lead to more ambiguity in the determination of λ_B from B →γ ℓν decay.