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 the $eta$ 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.
We present a new calculation of the semileptonic tree-level and flavor-changing neutral current form factors describing $B$-meson transitions to tensor mesons $T=D_2^*,K_2^*,a_2,f_2$ ($J^{P}=2^{+}$). We employ the QCD Light-Cone Sum Rules approach wi
th $B$-meson distribution amplitudes. We go beyond the leading-twist accuracy and provide analytically, for the first time, higher-twist corrections for the two-particle contributions up to twist four terms. We observe that the impact of higher twist terms to the sum rules is noticeable. We study the phenomenological implications of our results on the radiative ${B} to K_2^{*}gamma$ and semileptonic ${B} to D_2^* ell {bar u}_ell$, ${B} to K_2^{*}ell^+ell^-$ decays.
The form factors of $gamma^* N rightarrow Delta(1600)$ transition is calculated within the light-cone sum rules assuming that $Delta^+(1600)$ is the first radial excitation of $Delta(1232)$. The $Q^2$ dependence of the magnetic dipole $tilde{G}_M(Q^2
)$, electric quadrupole $tilde{G}_E(Q^2)$, and Coulomb quadrupole $tilde{G}_c(Q^2)$ form factors are investigated. Moreover, the $Q^2$ dependence of the ratios $R_{EM} = -frac{tilde{G}_E(Q^2)}{tilde{G}_M{Q^2}}$ and $R_{SM} = - frac{1}{4 m_{Delta(1600)}^2} sqrt{4 m_{Delta(1600)}^2 Q^2 + (m_{Delta(1600)}^2 - Q^2 - m_N^2)^2} frac{tilde{G}_c(Q^2)}{tilde{G}_M(Q^2)}$ are studied. Finally, our predictions on $tilde{G}_M(Q^2)$, $tilde{G}_E(Q^2)$, and $tilde{G}_C(Q^2)$ are compared with the results of other theoretical approaches.
We present a new calculation of the $Dtopi$ and $D to K$ form factors from QCD light-cone sum rules. The $overline{MS}$ scheme for the $c$-quark mass is used and the input parameters are updated. The results are $f^+_{Dpi}(0)= 0.67^{+0.10}_{-0.07}$,
$f^+_{DK}(0)=0.75^{+0.11}_{-0.08}$ and $f^+_{Dpi}(0)/f^+_{DK}(0)=0.88 pm 0.05$. Combining the calculated form factors with the latest CLEO data, we obtain $|V_{cd}|=0.225pm 0.005 pm 0.003 ^{+0.016}_{-0.012}$ and $|V_{cd}|/|V_{cs}|= 0.236pm 0.006pm 0.003pm 0.013$ where the first and second errors are of experimental origin and the third error is due to the estimated uncertainties of our calculation. We also evaluate the form factors $f^-_{Dpi}$ and $f^-_{DK}$ and predict the slope parameters at $q^2=0$. Furthermore, calculating the form factors from the sum rules at $q^2<0$, we fit them to various parameterizations. After analytic continuation, the shape of the $Dto pi,K $ form factors in the whole semileptonic region is reproduced, in a good agreement with experiment.
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.