Insights into the higher-twist distribution e(x)e(x) at CLAS

We present the extraction of the twist-3 PDF, $e(x)$, through the analysis of the preliminary data for the $\sin\phi$-moment of the beam-spin asymmetry for di-hadron Semi-Inclusive DIS at CLAS at 6 GeV. Pion-pair production off unpolarized target in the DIS regime provide an access to the higher-twist Parton Distribution Functions $e(x)$ and to Di-hadron Fragmentation Functions. The latter have been extracted from the semi-inclusive production of two hadron pairs in back-to-back jets in $e^+e^-$ annihilation at Belle. The $e(x)$ PDF offers important insights into the physics of the largely-unexplored quark-gluon correlations, and its $x$-integral is related to the marginally-known scalar-charge of the nucleon, and to the pion-nucleon $\sigma$-term, a fundamental property of the nucleon

The Tensor and the Scalar Charges of the Nucleon from Hadron Phenomenology

We discuss the impact of the determination of the nucleon tensor charge on searches for physics Beyond the Standard Model. We also comment on the future extraction of the subleading-twist PDF $e(x)$ from Jefferson Lab soon-to-be-released Beam Spin Asymmetry data as well as from the expected data of CLAS12, as the latter is related to the scalar charge. These analyses are possible through the phenomenology of Dihadron Fragmentation Functions related processes, which we report on here as well.Comment: To appear in the proceedings of the ISMD 2017, held in Tlaxcala, Mexico, September 11-15, 2017. Includes .cls and .bst files for EPJ Web of Conferences. arXiv admin note: substantial text overlap with arXiv:1608.0442

The Pion-Photon Transition Distribution Amplitudes in the Nambu-Jona Lasinio Model

We define the pion-photon Transition Distribution Amplitudes (TDA) in a field theoretic formalism from a covariant Bethe-Salpeter approach for the determination of the bound state. We apply our formalism to the Nambu - Jona Lasinio model, as a realistic theory of the pion. The obtained vector and axial TDAs satisfy all features required by general considerations. In particular, sum rules and polynomiality condition are explicitly verified. We have numerically proved that the odd coefficients in the polynomiality expansion of the vector TDA vanish in the chiral limit. The role of PCAC and the presence of a pion pole are explicitly shown.Comment: 14 pag. and 6 fig, final version (to appear in Phys. Rev. D

The Strong Coupling Constant from Hadron Structure Phenomenology

We present recent developments on the role of the running coupling constant at the intersection of perturbative and nonperturbative QCD. A number of experiments show a smooth transition from small to large scales given by the four-momentum transfer in the reactions. This is at variance with perturbative QCD where the running coupling constant becomes infinite when the scale equals $\Lambda_{{\tiny QCD}}$. Approaches using an effective coupling constant could help interpret the opposite trend of data as compared to standard perturbative QCD predictions. We give an overview of the role of the coupling constant in the procedure to match nonperturbative hadronic model to perturbative QCD and we propose an extraction of an effective coupling constant from inclusive electron proton scattering data at large Bjorken x.Comment: To appear in the proceedings of the QCD Evolution Workshop, JLab, May 14-17, 2012. Includes ws-ijmpcs.cl

Distribution amplitude for the photon-pion transition

The exclusive production of \pi\pi and \pi\rho in hard \gamma^{\star}\gamma scattering in the forward kinematical region where the virtual photon is highly off-shell are studied through the \gamma\to\pi^- Transition Distribution Amplitudes. The calculation is based on a covariant Bethe-Salpeter approach, applied to the Nambu - Jona-Lasinio model, for the determination of the pion bound state. In particular it is shown that the pion pole contribution produces a large enhancement of the differential cross section for the pion pair production with respect to previous estimates.Comment: To appear in the proceedings of Light Cone 2008: Relativistic Nuclear and Particle Physics (LC2008), Mulhouse, France, 7-11 Jul 200

Model calculations of the Sivers function satisfying the Burkardt Sum Rule

It is shown that, at variance with previous analyses, the MIT bag model can explain the available data of the Sivers function and satisfies the Burkardt Sum Rule to a few percent accuracy. The agreement is similar to the one recently found in the constituent quark model. Therefore, these two model calculations of the Sivers function are in agreement with the present experimental and theoretical wisdom.Comment: 9 pages, 4 figures; one figure added; references added; slightly revised version accepted for publication in Phys. Rev.

The Dihadron fragmentation functions way to Transversity

Observations of the transversity parton distribution based on an analysis of pion-pair production in deep inelastic scattering off transversely polarized targets are presented. This extraction relies on the knowledge of dihadron fragmentation functions, which are obtained from electron-positron annihilation measurements. This is the first attempt to determine the transversity distribution in the framework of collinear factorization.Comment: To appear in the proceedings of XIX International Workshop on Deep-Inelastic Scattering and Related Subjects (DIS 2011), April 11-15, 2011, Newport News, VA USA ; AIP style files include