Wei, ZT (reprint author), CCAST, World Lab, POB 8730, Beijing 100080, Peoples R China.
The study of exclusive B decays in perturbative QCD are complicated by the endpoint problem. In order to perform the perturbative calculation, the Sudakov effects are introduced to regulate the endpoint singularity. We provide a systematic analysis with leading and next-to-leading twist corrections for B --> pi form factors in pQCD approach. The intrinsic transverse momentum dependence of hadronic wave function and threshold resummation effects are included in pQCD approach. There are two leading twist B meson distribution amplitudes (or generally wave functions) in general. The QCD equations of motion provide important constraints on B meson wave functions. The reliability of pQCD approach in B --> pi form factors is discussed. 70% of the result comes from the region alpha(s)(t)/pi < 0.2 and 38% comes from the region where the momentum transfer t greater than or equal to 1 GeV. The conceptual problems of pQCD approach are discussed in brief. Our conclusion is that pQCD approach in the present form cannot provide a precise prediction for B --> pi transition form factors. (C) 2002 Elsevier Science B.V. All rights reserved.