Investigating GPDs in the framework of the double distribution model

In this paper, we construct the generalized parton distribution (GPD) in terms of the kinematical variables [Formula: see text], [Formula: see text], [Formula: see text], using the double distribution model. By employing these functions, we could extract some quantities which makes it possible to gain a three-dimensional insight into the nucleon structure function at the parton level. The main objective of GPDs is to combine and generalize the concepts of ordinary parton distributions and form factors. They also provide an exclusive framework to describe the nucleons in terms of quarks and gluons. Here, we first calculate, in the Double Distribution model, the GPD based on the usual parton distributions arising from the GRV and CTEQ phenomenological models. Obtaining quarks and gluons angular momenta from the GPD, we would be able to calculate the scattering observables which are related to spin asymmetries of the produced quarkonium. These quantities are represented by [Formula: see text] and [Formula: see text]. We also calculate the Pauli and Dirac form factors in deeply virtual Compton scattering. Finally, in order to compare our results with the existing experimental data, we use the difference of the polarized cross-section for an initial longitudinal leptonic beam and unpolarized target particles [Formula: see text]. In all cases, our obtained results are in good agreement with the available experimental data.

A NONEXTENSIVE STATISTICAL MODEL FOR THE NUCLEON STRUCTURE FUNCTION

We studied an application of nonextensive thermodynamics to describe the structure function of nucleon, in a model where the usual Fermi–Dirac and Bose–Einstein energy distribution were replaced by the equivalent functions of the q-statistical. The parameters of the model are given by an effective temperature T, the q parameter (from Tsallis statistics), and two chemical potentials given by the corresponding up (u) and down (d) quark normalizations in the nucleon.

Transverse Spin Structure Function

The transverse spin-dependent nucleon structure function at large is computed within the Wandzura-Wilczek relation, using NLO fit. Also we investigate the twist-3 contribution of via calculating . It turns out that although the twist-3 part of can be negligible for DIS processes, it has a significant value in resonance region.

EXPLICIT MODEL REALIZING PARTON–HADRON DUALITY

We present a model that realizes both resonance-Regge (Veneziano) and parton–hadron (Bloom–Gilman) duality. We first review the features of the Veneziano model and we discuss how parton–hadron duality appears in the Bloom–Gilman model. Then we review limitations of the Veneziano model, namely that the zero-width resonances in the Veneziano model violate unitarity and Mandelstam analyticity. We discuss how such problems are alleviated in models that construct dual amplitudes with Mandelstam analyticity (so-called DAMA models). We then introduce a modified DAMA model, and we discuss its properties. We present a pedagogical model for dual amplitudes and we construct the nucleon structure function F2(x, Q2). We explicitly show that the resulting structure function realizes both Veneziano and Bloom–Gilman duality.

(ANTI-)STRANGE DENSITY AND CONTRIBUTION OF HEAVY FLAVOR, $F_2^c$, TO THE NUCLEON STRUCTURE FUNCTION IN THE CHIRAL QUARK MODEL

A new approach is employed to provide the required expressions for the bare constituent quark densities in the proton. In this approach, we assume the bare quark densities take a Gaussian form in four-momentum space, which fulfill more properly the desired constrains of parton densities inside the proton. Using the modified chiral quark model and the related convolutions, the parton densities inside the proton are obtained. By evolving the gluon density to high energy scale, the contribution of charm quark to the proton structure function can be extracted and it is found in good agreement with the available experimental data. Sea quark ((anti-)strange) densities are calculated and compared with the ones from some phenomenological and experimental groups in which consistent results are obtained. What makes the results more valuable is that the initial framework is completely theoretical and we do not need to resort to any parametrizations in our calculations.

NON-SINGLET PART OF THE LONGITUDINAL STRUCTURE FUNCTION FL UP TO $O(\alpha_s^3)$

The unpolarized longitudinal nucleon structure function FL, measured in the deep inelastic lepton-nucleon scattering, is contained of three parts, singlet, non-singlet and gluon. The aim of this paper is to perform a QCD analysis of the longitudinal heavy and light structure functions FL(x, Q2) in the non-singlet part up to [Formula: see text]. We use the light and heavy flavor Wilson coefficients and distribution functions in Mellin space. Also we need to use the Padé approximation for αs analysis.