Transverse Momentum Dependent Factorization for Radiative Leptonic Decay of B-Meson

Abstract

With a consistent definition of transverse-momentum-dependent(TMD) light-cone wave function of $B$-meson, we show that the amplitude of the radiative leptonic B-decay can be factorized at one-loop level as a convolution with the wave function and a perturbative coefficient function, combined with a soft factor. In this TMD factorization, the transverse momenta of partons in the $B$-meson are taken into account and all soft divergences are contained in the wave function and the soft factor. The coefficient function is infrared-safe. The factorization works on a diagram-by-diagram basis and is possible to extend beyond one loop. With the factorization the large logarithms in the perturbative function can be simply resummed. Our work shows that the result of collinear factorization for the decay can be derived from that of TMD factorization. Therefore, the two factorizations for the case here are simply related to each other.