No abstract

New sum rules for B → π, K and B → ρ, K * form factors are derived from the correlation functions expanded near the light-cone in terms of B-meson distribution amplitudes. The contributions of quark-antiquark and quark-antiquark-gluon components in the B meson are taken into account. Models for the B-meson three-particle distribution amplitudes are suggested, based on QCD sum rules in HQET. Employing the new light-cone sum rules we calculate the form factors at small momentum transfers, including SU (3)-violation effects. The results agree with the predictions of the conventional light-cone sum rules.

We reconsider and update the QCD light-cone sum rules for B → π form factors. The gluon radiative corrections to the twist-2 and twist-3 terms in the correlation functions are calculated. The M S b-quark mass is employed, instead of the one-loop pole mass used in the previous analyses. The light-cone sum rule for f + Bπ (q 2 ) is fitted to the measured q 2 -distribution in B → πlν l , fixing the input parameters with the largest uncertainty: the Gegenbauer moments of the pion distribution amplitude. For the B → π vector form factor at zero momentum transfer we predict f + Bπ (0) = 0.26 +0.04 −0.03 . Combining it with the value of the product |V ub f + Bπ (0)| extracted from experiment, we obtain |V ub | = (3.5 ± 0.4 ± 0.2 ± 0.1) × 10 −3 . In addition, the scalar and penguin B → π form factors f 0 Bπ (q 2 ) and f T Bπ (q 2 ) are calculated.