Related papers: Quark-Hadron Duality and $\gamma^* p \to \Delta$ F…
We use local quark-hadron duality to estimate the purely nonperturbative soft contribution to the $\gamma^* p \to \Delta$ form factors. Our results are in agreement with existing experimental data. We predict that the ratio…
The purely nonperturbative soft contribution to the $\gamma^* p \to \Delta^+$ transition form factors is estimated using the local quark-hadron duality approach. Our results show that the soft contribution is dominated by the magnetic…
We discuss two types of contributions to hadronic form factors in QCD: hard gluon exchange and soft wave function overlap. Within the QCD sum rule approach, the hard contribution has strong numeric suppression by factor (\alpha_s/\pi) ~ 0.1…
The local-duality formulation of QCD sum rules allows for the prediction of hadronic form factors without knowledge of the subtle details of their structure. With the aid of this formalism, we take a fresh look at the behaviours of the…
We present an updated extraction of the proton electromagnetic form factor ratio, mu_p G_E/G_M, at low Q^2. The form factors are sensitive to the spatial distribution of the proton, and precise measurements can be used to constrain models…
The three electromagnetic form factors of the $\Delta(1232)$ resonance, $G^*_M(q^2)$, $G^*_E(q^2)$, and $G^*_C(q^2)$ are obtained in the space-like region using a Dual Resonance Model realization of QCD in the large $N_c$ limit…
In this talk I report on recent progress in a few areas closely related to the virtual Compton scattering studies. In particular, I discuss the quark-hadron duality estimate of the $\gamma^* p \to \Delta^+$ transition, QCD sum rule…
The meson-photon transition form factors $\gamma\gamma^*\to P$ ($P$ stands for $\pi$, $\eta$ and $\eta'$) provide strong constraints on the distribution amplitudes of the pseudoscalar mesons. In this paper, these transition form factors are…
Recent experiment indicates that the behavior exhibited by the ratios $E_{1^+}/M_{1^+}$ and $S_{1^+}/M_{1^+}$ of the $\gamma^* N \leftrightarrow \Delta$ transition remain small and negative for $Q^2 \le 4.0 GeV^2$. It implies that the…
This work addresses the calculation of local form factors involved in the theoretical predictions of semileptonic $B$-meson decays at low $q^2$. We present a new approach to the method of QCD light-cone sum rule with $B$-meson light-cone…
We analyze the electromagnetic pion and kaon form factor by including radiative and higher-twist effects within the framework of resummed pQCD in the space-like region. We focus on the transition from the perturbative to non-perturbative…
Quark-hadron duality is an interesting and potentially very useful phenomenon, as it relates the properly averaged hadronic data to a perturbative QCD result in some kinematic regions. While duality is well established experimentally, our…
It is demonstrated in several exclusive processes involving the pion that a local quark-hadron duality prescription is equivalent to using an effective $ \bar q q $ (two-body) light-cone wave function $\Psi^{(LD)}(x,k_{\perp})$ for the…
The method of light-cone QCD sum rules is applied to the calculation of the form factors of $\gamma^*\rho \to \pi$ and $\gamma^*\gamma \to \pi^0$ transitions. We consider the dispersion relation for the $\gamma^*(Q^2)\gamma^*(q^2) \to…
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…
The \gamma* N -> \Delta(1232) transition is a window on hadron shape deformation, the applicability of perturbative QCD at moderate momentum transfers, and the influence of nonperturbative phenomena on hadronic observables. We explain that…
Recent studies of the Q^2 dependence of ep scattering in the large x region and in the Q^2 range: 1 < Q^2 <leq 30 Gev^2, confirm the validity of the phenomenon of quark-hadron duality - the similarity of the deep inelastic (parton) and…
We present a leading-order pQCD calculation of the helicity-flip $\Delta\to N\gamma^*$ matrix element $G_0$ (Coulomb quadrupole amplitude $C2$), taking into account the transverse momenta of the quarks and the contribution from the gluons.…
We study the $P\to\gamma\,\gamma^*$ ($P=\pi^0,\eta,\eta'$) transition form factors by means of the local-duality (LD) version of QCD sum rules. For the case of $\eta$ and $\eta'$, the conventional LD model provides a good description of the…
While quark-hadron duality is well-established experimentally, the current theoretical understanding of this important phenomenon is quite limited. To expose the essential features of the dynamics behind duality, we use a simple model in…