Coulomb Distortion in Quasielastic (e,e′)(e,e') Scattering on Nuclei: Effective Momentum Approximation and Beyond

The role of the effective momentum approximation to disentangle Coulomb distortion effects in quasielastic $(e,e')$ reactions is investigated. The separation of the cross section in longitudinal and transverse components is discussed including higher order DWBA corrections due to the focusing of the electron waves.The experimental studies performed, in the last few years, making use of different approximate treatments are shown to be sometime inconsistent. As a consequence some of the longitudinal and transverse responses, extracted from the inclusive cross sections cannot be considered reliable. A separation procedure based on the effective momentum approximation is discussed in connection with the recent experimental data on electron/positron quasielastic scattering on $^{12}$C and $^{208}$Pb.Comment: latex, no figures, submitted to Nucl. Phys.

Hadronic degrees of freedom

I report on the research activities performed under the (italian) MURST-PRIN project "Fisica Teorica del Nucleo e dei sistemi a pi\'u corpi" covering part of the topics on hadronic degrees of freedom. The most recent achievements in the field are summarized focusing on the specific role of the nuclear physics community.Comment: To appear in the Proceedings of 8th Convegno su Problemi di Fisica Nucleare Teorica (Cortona 2000), Cortona, Italy, 18-21 Oct. 2000, uses ws-p8-50x6-00.cl

Parton distributions in a constituent quark scenario

A simple picture of the constituent quark as a composite system of point-like partons is used to construct the unpolarized and polarized parton distributions by a convolution between constituent quark momentum distributions and constituent quark structure functions. We achieve good agreement with experiments in the unpolarized, as well as, in the polarized case. When our results are compared with similar calculations using non-composite constituent quarks, the accord with the experiments of the present scheme is impressive. We conclude that DIS data are consistent with a low energy scenario dominated by composite constituents of the nucleon.Comment: 4 pages; latex using espcrc1.sty; 4 postscript figures; Invited talk at the Workshop ``Nucleon '99'', Frascati; Italy 7-9 June 1999. Submitted to Nuc. Phys.

Double parton correlations in Light-Front constituent quark model

Double parton distribution functions (dPDF) represent a tool to explore the 3D proton structure. They can be measured in high energy proton-proton and proton nucleus collisions and encode information on how partons inside a proton are correlated among each other. dPFDs are studied here in the valence quark region, by means of a constituent quark model, where two particle correlations are present without any additional prescription. This framework allows to understand the dynamical origin of the correlations and to clarify which, among the features of the results, are model independent. Use will be made of a relativistic light-front scheme, able to overcome some drawbacks of the previous calculation. Transverse momentum correlations, due to the exact treatment of the boosts, are predicted and analyzed. The role of spin correlations is also shown. Due to the covariance of the approach, some symmetries of the dPDFs are seen unambigously. For the valence sector, the study of the QCD evolution of the model results, which can be performed safely thanks to the property of good support, has been also completed.Comment: 8 pages, 12 figures, invited talk at the "XLIV ISMD Conference", Bologna, Italy, 8-12 September 2014. Submitted to EPJ Web of Conference

A model calculation of double parton distribution functions of the pion

Two-parton correlations in the pion are investigated in terms of double parton distribution functions. A Poincar\'e covariant Light-Front framework has been adopted. As non perturbative input, the pion wave function obtained within the so-called soft-wall AdS/QCD model has been used. Results show how novel dynamical information on the structure of the pion, not accessible through one-body parton distribution, are encoded in double parton distribution functions.Comment: 14 pages, 8 figure