We investigate the effect of different forms of relativistic spin coupling of constituent quarks in the nucleon electromagnetic form factors. The fourdimensional integrations in the two-loop Feynman diagram are reduced to the null-plane, such that the light-front wave function is introduced in the computation of the form factors. The neutron charge form factor is very sensitive to different choices of spin coupling schemes, once its magnetic moment is fitted to the experimental value. The scalar coupling between two quarks is preferred by the neutron data, when a reasonable fit of the proton magnetic momentum is found.

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The bound state of constituent quarks forming a Qqq composite baryon is investigated in a QCD-inspired effective light-front model. The light-front Faddeev equations are derived and solved numerically. The masses of the spin 1/2 low-lying states of the nucleon, ⌳ 0 , ⌳ c ϩ and ⌳ b 0 , are found and compared to the experimental data. The data are qualitatively described with a flavor independent effective interaction.

We investigate the effect of different forms of relativistic spin coupling of constituent quarks on the nucleon electroweak properties. The correlations between the static electroweak observables are found to be independent of the shape of momentum part of the nucleon light-front wave function within each quark spin coupling scheme. The neutron charge form factor is very sensitive to different choices of spin coupling schemes once its magnetic moment is fitted to the experimental value, while it is found insensitive to the details of the momentum part of the three-quark wave function model. The scalar pair from the coupling of two constituent quarks is preferred by the neutron charge form factor data for momentum transfers below 1 (GeV/c) 2 , independent of the shape of the wave function.

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