Generalized Parton Distributions in the Light-Front Constituent Quark Model

The Generalized Parton Distributions (GPDs) of the nucleon are analyzed within the relativistic constituent quark model formulated on the light-front. It is shown that the matrix elements of the plus component of the one-body vector current are plagued by spurious effects related to the dependence on the hyperplane where the nucleon wave function is defined in terms of its constituents. The physical GPDs can be extracted only from the matrix elements of a transverse component of the one-body current. The loss of the polinomiality property is then related to the neglect of the pair creation process for non-vanishing values of the skewness. The need of implementing effective many-body currents corresponding to the Z-graph is stressed and a possible approach to achieve such a goal is proposed. aTo appear in the Proceedings of the International Conference on The Physics of excited Nucleons (N∗ 2004), Grenoble (France), March 24-27, 2004, World Scientific Publishing (Singapore), in press.