Generalized Parton Distribution Functions Research Articles

Generalized parton distribution functions and the nucleon spin sum rules in the chiral quark soliton model

The theoretical predictions are given for the forward limit of the unpolarized spin-flip isovector generalized parton distribution function $(E^u - E^d)(x, \xi, t)$ within the framework of the chiral quark soliton model, with full inclusion of the polarization of Dirac sea quarks. We observe that $[(H^u - H^d) + (E^u - E^d)](x,0,0)$ has a sharp peak around $x=0$, which we interpret as a signal of the importance of the pionic $q \bar{q}$ excitation with large spatial extension in the transverse direction. Another interesting indication given by the predicted distribution in combination with Ji's angular momentum sum rule is that the $\bar{d}$-quark carries more angular momentum than the $\bar{u}$-quark in the proton, which may have some relation with the physics of the violation of the Gottfried sum rule.

Generalized parton distribution function(Eu+Ed)(x,ξ,t)of the nucleon in the chiral quark soliton model

The unpolarized spin-flip isoscalar generalized parton distribution function $({E}^{u}+{E}^{d})(x,\ensuremath{\xi},t)$ is studied in the large-${N}_{c}$ limit at a low normalization point in the framework of the chiral quark-soliton model. This is the first study of generalized parton distribution functions in this model, which appear only at the subleading order in the large-${N}_{c}$ limit. Particular emphasis is put therefore on the demonstration of the theoretical consistency of the approach. The forward limit of $({E}^{u}+{E}^{d})(x,\ensuremath{\xi},t)$ of which only the first moment--the anomalous isoscalar magnetic moment of the nucleon--is known phenomenologically, is computed numerically. Observables sensitive to $({E}^{u}+{E}^{d})(x,\ensuremath{\xi},t)$ are discussed.

Generalized parton distributions from lattice QCD.

We perform a quenched lattice calculation of the first moment of twist-two generalized parton distribution functions of the proton, and assess the total quark (spin and orbital angular momentum) contribution to the spin of the proton.

Single-spin asymmetry parameter from deeply virtual Compton scattering of hadrons up to twist-3 accuracy

The study of deeply virtual Compton scattering (DVCS) has shown that electromagnetic gauge invariance requires, to leading order, not only twist-two but additional twist-three contributions. We apply this analysis and, using the Ellis-Furmanski-Petronzio factorization scheme, compute the single- (electron) spin asymmetry arising in the collision of longitudinally polarized electrons with hadrons up to twist-3 accuracy. In order to simplify the kinematics we restrict the actual calculation to pions in the chiral limit. The process is described in terms of the generalized parton distribution functions which we obtain within a bag model framework.