Improved analysis of B→π e ν from QCD sum rules on the light-cone

We present a new calculation of the B-->pi form-factor f(+), relevant for the measurement of \V-ub\ from semileptonic B-->pi transitions, from QCD sum rules on the light-cone. The new element is the calculation of radiative corrections to next-to-leading twist-3 accuracy. We find that these contributions are factorizable at O(alpha(s)), which lends additional support to the method of QCD sum rules on the light-cone. We obtain f(+)(0) = 0.26+/-0.06+/-0.05, where the first error accounts for the uncertainty in the input-parameters and the second is a guesstimate of the systematic uncertainty induced by the approximations inherent in the method. We also obtain a simple parametrization of the form-factor which is valid in the entire kinematical range of semileptonic decays and consistent with vector-meson dominance at large momentum-transfer.