Related papers: Stability Analysis of Sum Rules for Compton Scatte…
I discuss in this talk the physics of the $Q^2$ dependence of the $G_1(x,Q^2)$ structure function sum rule. For $Q^2>3$ GeV$^2$, the $Q^2$ variation is controlled by pure QCD radiative corrections. For $0.5<Q^2<3$ GeV$^2$, the twist-four…
The relativistic scattering of a spin-1/2 particle from an infinitely long solenoid is considered in the framework of covariant perturbation theory. The first order term agrees with the corresponding term in the series expansion of the…
We develop a formalism to calculate form factor and charge density distribution of pion in the chiral limit using the holographic dual model of QCD with hard-wall cutoff. We introduce two conjugate pion wave functions and present analytic…
We discuss the pion form factor calculation in QCD.We shortly consider the main points of the nonlocal condensate QCD sum rule approach and show its results for the pion form factor, $F_\pi(Q^2)$. These results are compared with predictions…
We present an improved Standard-Model (SM) prediction for the dilepton decay of the neutral pion. The loop amplitude is determined by the pion transition form factor for $\pi^0\to\gamma^*\gamma^*$, for which we employ a dispersive…
We calculate the forward spin-dependent photon-nucleon Compton amplitudes $S_1$ and $S_2$ as functions of photon energy $\nu$ and mass $Q^2$ at the next-to-leading (${\cal O}(p^4)$) order in chiral perturbation theory, from which we extract…
In response to Kim's comment (nucl-th/9903040) on the sum rules for pion-baryon coupling constants obtained in hep-ph/9512259 and hep-ph/9606471, we point out that our treatment of the continuum is consistent with duality and with the fact…
This review article discusses the experimental and theoretical status of various Parton Model sum rules. The basis of the sum rules in perturbative QCD is discussed. Their use in extracting the value of the strong coupling constant is…
We extend the investigation of the Generalized Parton Distribution for a charged pion within a fully covariant constituent quark model, in two respects: (i) calculating the tensor distribution and (ii) adding the treatment of the evolution,…
We compute the scattering amplitude for pion scattering in Wilson chiral perturbation theory for two degenerate quark flavors. We consider two different regimes where the quark mass m is of order (i) a\Lambda_QCD^2 and (ii)…
Momentum sum rule can be used as an inequality to estimate the lower and upper bounds of the momentum fractions of quarks and gluons in a model of proton valid in a limited \textit{x} range. We compute such bounds in a self-similarity based…
The nonperturbative $Q^2$- dependence of the sum rules for the structure functions of polarized $e(\mu)N$ scattering is discussed. The determination of twist-4 corrections to the structure functions at high $Q^2$ by QCD sum rules is…
We present a lattice QCD calculation of the double-virtual neutral pion transition form factor, with the goal to cover the kinematic range relevant to hadronic light-by-light scattering in the muon $g-2$. Several improvements have been made…
The status of Compton scattering by the nucleon at energies of the first and second resonance is summarized. In addition to a general test of dispersion theories and a precise determination of polarizabilities, the validities of four…
The pion-pole contribution to hadronic light-by-light scattering in the anomalous magnetic moment of the muon $(g-2)_\mu$ is fully determined by the doubly-virtual pion transition form factor. Although this crucial input quantity is, in…
We re-analyze data on deep inelastic polarized lepton-nucleon scattering, with particular attention to testing the Bjorken sum rule and estimating the quark contributions to the nucleon spin. Since only structure function data at fixed…
We discuss a consistent treatment of the light-front gauge-boson and meson wave functions in the analyses of the generalized parton distributions(GPDs) and the scattering amplitudes in deeply virtual Compton scattering(DVCS) for the pion.…
The pion structure function is investigated in a simple model, where pion and constituent quark fields are coupled through the simplest pseudoscalar coupling. The imaginary part of the forward gamma* pi-> gamma* pi scattering amplitude is…
Recent measurement of the $\gamma\gamma^\ast$ form factor of the neutral pion in the high $Q^2$ region disagrees with {\em a priori} predictions of QCD-based calculations. We comment on existing explanations, and analyze a possibility that…
We present a parameterization of the non-collinear (virtual) Compton scattering tensor in terms of form factors, in which the Lorentz tensor associated with each form factor possesses manifest electromagnetic gauge invariance. The main…