The spin structure of the nucleon in light-cone quark models

The quark spin densities related to generalized parton distributions in impact-parameter space and to transverse-momentum dependent parton distributions are reviewed within a light-cone quark model, with focus on the role of the different spin-spin and spin-orbit correlations of quarks.Results for azimuthal spin asymmetries in semi-inclusive deep-inelastic scattering due to T-even transverse-momentum dependent parton distributions are also discussed.Comment: proceedings of the workshop "Recent Advances in Perturbative QCD and Hadronic Physics", 20-25 July 2009, ECT*, Trento (Italy), in Honor of Prof. Anatoly Efremov's 75th Birthday Celebration; also based on the talk given at the workshop "Transverse Partonic Structure of Hadrons", 21-26 June 2009, Yerevan (Armenia); to appear in Mod. Phys. Lett.

Transverse pion structure beyond leading twist in constituent models

The understanding of the pion structure as described in terms of transverse-momentum dependent parton distribution functions (TMDs) is of importance for the interpretation of currently ongoing Drell-Yan experiments with pion beams. In this work we discuss the description of pion TMDs beyond leading twist in a pion model formulated in the light-front constituent framework. For comparison, we also review and derive new results for pion TMDs in the bag and spectator models.Comment: 17 pages, 7 figures; v2: modified presentation, updated references; matches the journal versio

Naive time-reversal odd phenomena in semi-inclusive deep-inelastic scattering from light-cone constituent quark models

We present results for leading-twist azimuthal asymmetries in semi-inclusive lepton-nucleon deep-inelastic scattering due to naively time-reversal odd transverse-momentum dependent parton distribution functions from the light-cone constituent quark model. We carefully discuss the range of applicability of the model, especially with regard to positivity constraints and evolution effects. We find good agreement with available experimental data from COMPASS and HERMES, and present predictions to be tested in forthcoming experiments at Jefferson Lab.Comment: 10 pages, 7 figures, discussion of evolution effects extended, to appear in Phys.Rev.