Three-Dimensional parton structure of light nuclei

Two promising directions beyond inclusive deep inelastic s cattering experiments, aimed at unveiling the three dimensional structure of the bo und nucleon, are reviewed, considering in particular the 3 He nuclear target. The 3D structure in coordinate space can be accessed through deep exclusive processes, whose non-pe rturbative part is encoded in generalized parton distributions. In this way, the distrib ution of partons in the transverse plane can be obtained. As an example of a deep exclusive proce ss, coherent deeply virtual Compton scattering (DVCS) off 3 He nuclei, important to access the neutron generalized part on distributions (GPDs), will be discussed. In Impulse Approx imation (IA), the sum of the two leading twist, quark helicity conserving GPDs of 3 He, H and E , at low momentum transfer, turns out to be dominated by the neutron contribution. Besid es, a technique, able to take into account the nuclear effects included in the Impulse Approxim ation analysis, has been developed. The spin dependent GPD ̃ H of 3 He is also found to be largely dominated, at low momentum transfer, by the neutron contribution. The knowledge of the GPDs H, E and ̃ H of 3 He is relevant for the planning of coherent DVCS off 3 He measurements. Semi-inclusive deep inelastic scattering processes access the momentum space 3D structur e parameterized through transverse momentum dependent parton distributions. A distorted spin -dependent spectral function has been recently introduced for 3 He, in a non-relativistic framework, to take care of the final state interaction between the observed pion and the remnant in sem i-inclusive deep inelastic electron scattering off transversely polarized 3 He. The calculation of the Sivers and Collins single spin asymmetries for 3 He, and a straightforward procedure to effectively take into account nuclear dynamics and final state interactions, will be reviewed. The Light-front dynamics generalization of the analysis is also addressed