Abstract:We calculate the long-distance effect generated by the four-quark operators with c-quarks in the B → K ( * ) ℓ + ℓ − decays. At the lepton-pair invariant masses far below thecc-threshold, q 2 ≪ 4m 2 c , we use OPE near the light-cone. The nonfactorizable softgluon emission from c-quarks is cast in the form of a nonlocal effective operator. The B → K ( * ) matrix elements of this operator are calculated from the QCD light-cone sum rules with the B-meson distribution amplitudes. As a byproduct, we also predict the charm-loop contribution to B → K * γ beyond the local-operator approximation. To describe the charmloop effect at large q 2 , we employ the hadronic dispersion relation with ψ = J/ψ, ψ(2S), ... contributions, where the measured B → K ( * ) ψ amplitudes are used as inputs. Matching this relation to the result of QCD calculation reveals a destructive interference between the J/ψ and ψ(2S) contributions. The resulting charm-loop effect is represented as a q 2 -dependent correction ∆C 9 (q 2 ) to the Wilson coefficient C 9 . Within uncertainties of our calculation, at q 2 below the charmonium region the predicted ratio ∆C 9 (q 2 )/C 9 is ≤ 5% for B → Kℓ + ℓ − , but can reach as much as 20% for B → K * ℓ + ℓ − , the difference being mainly caused by the soft-gluon contribution.

We calculate the D * Dπ and B * Bπ couplings using QCD sum rules on the lightcone. In this approach, the large-distance dynamics is incorporated in a set of pion wave functions. We take into account two-particle and three-particle wave functions of twist 2, 3 and 4. The resulting values of the coupling constants are g D * Dπ = 12.5 ± 1 and g B * Bπ = 29 ± 3. From this we predict the partial width Γ(D * + → D 0 π + ) = 32 ± 5 keV . We also discuss the soft-pion limit of the sum rules which is equivalent to the external axial field approach employed in earlier calculations. Furthermore, using g B * Bπ and g D * Dπ the pole dominance model for the B → π and D → π semileptonic form factors is compared with the direct calculation of these form factors in the same framework of light-cone sum rules.

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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.

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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.

We calculate the form factors for the heavy-to-light transitions B → π, K by means of QCD sum rules using π and K light-cone wave functions. Higher twist contributions as well as gluonic corrections are taken into account. The sensitivity to the shape of the leading-twist wave functions and effects of SU(3)-breaking are discussed. The results are compared with quark model predictions and with the results from QCD sum rules for three-point correlators.