We find that the evolution equation for the three-particle quark-gluon B-meson light-cone distribution amplitude (DA) of subleading twist is completely integrable in the large $N_c$ limit and can be solved exactly. The lowest anomalous dimension is s
eparated from the remaining, continuous, spectrum by a finite gap. The corresponding eigenfunction coincides with the contribution of quark-gluon states to the two-particle DA $phi_-(omega)$ so that the evolution equation for the latter is the same as for the leading-twist DA $phi_+(omega)$ up to a constant shift in the anomalous dimension. Thus, ``genuine three-particle states that belong to the continuous spectrum effectively decouple from $phi_-(omega)$ to the leading-order accuracy. In turn, the scale dependence of the full three-particle DA turns out to be nontrivial so that the contribution with the lowest anomalous dimension does not become leading at any scale. The results are illustrated on a simple model that can be used in studies of $1/m_b$ corrections to heavy-meson decays in the framework of QCD factorization or light-cone sum rules.
We update the theoretical framework for the QCD calculation of transition form factors $gamma^*gammatoeta$ and $gamma^*gammatoeta$ at large photon virtualities including full next-to-leading order analysis of perturbative corrections, the charm quark
contribution, and taking into account SU(3)-flavor breaking effects and the axial anomaly contributions to the power-suppressed twist-four distribution amplitudes. The numerical analysis of the existing experimental data is performed with these improvements.
We study the electromagnetic nucleon form factors within the approach based on light-cone sum rules. We include the next-to-leading-order corrections for the contributions of twist-three and twist-four operators and a consistent treatment of the nucl
eon mass corrections in our calculation. It turns out that a self-consistent picture arises when the three valence quarks carry $40%:30%:30%$ of the proton momentum.
We derive light-cone sum rules for the electromagnetic nucleon form factors including the next-to-leading-order corrections for the contribution of twist-three and twist-four operators and a consistent treatment of the nucleon mass corrections. The e
ssence of this approach is that soft Feynman contributions are calculated in terms of small transverse distance quantities using dispersion relations and duality. The form factors are thus expressed in terms of nucleon wave functions at small transverse separations, called distribution amplitudes, without any additional parameters. The distribution amplitudes, therefore, can be extracted from the comparison with the experimental data on form factors and compared to the results of lattice QCD simulations. A selfconsistent picture emerges, with the three valence quarks carrying 40%:30%:30% of the proton momentum.
We present an improved light-cone sum rule analysis of the decay form factors of $D$ and $D_s$ into $eta$ and $eta^{prime}$ and argue that these decays offer a very promissing possibility to determine the leading Fock-state gluonic contribution of th
e $eta$ at future experimental facilities as FAIR or Super-KEKB. We also give the corresponding branching ratios for B decays.
We provide a theoretical update of the calculations of the pi0-gamma*-gamma form factor in the LCSR framework, including up to six polynomials in the conformal expansion of the pion distribution amplitude and taking into account twist-six corrections
related to the photon emission at large distances. The results are compared with the calculations of the B-> pi l nu decay and pion electromagnetic form factors in the same framework. Our conclusion is that the recent BaBar measurements of the pi0-gamma*-gamma form factor at large momentum transfers are consistent with QCD, although they do suggest that the pion DA may have more structure than usually assumed.
