Improved analysis ofB!e from QCD sum rules on the light-cone

We present a new calculation of the B ! form-factorf+, relevant for the measurement ofjVubjfrom semileptonicB!transitions, from QCD sum rules on the light-cone. The new element is the calculation of radiative corrections tonext-to-leadingtwist-3accuracy. Wendthatthesecontributionsarefactorizable atO(s), which lends additional support to the method of QCD sum rules on the light-cone. Weobtainf+(0)=0:260:060:05,wherethersterroraccountsforthe uncertaintyintheinput-parametersandthesecondisaguesstimateofthesystematic 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.