He, J (reprint author), CCAST, World Lab, POB 8730, Beijing 100080, Peoples R China.
We use a diquark model of the nucleon to calculate the electromagnetic forrn factors of the nucleon described as a scalar and axialvector diquark bound state. We provide an analysis of the zero-mode contribution in the diquark model. We find that there are zero-mode contributions to the form factors arising from the instantaneous part of the quark propagator, which cannot be neglected compared with the valence contribution but can be removed by the choice of wavefunction. We also find,that the charge, magnetic radii and magnetic moment of the proton can be reproduced, while the magnetic moment of the neutron is too small. The dipole shape of the form factors. G(M)(P) (Q(2))/mu(p) and G(M)(n) (Q(2))/mu(n,beta) can be reproduced. The ratio mu G(E)(P)/G(M)(P) decreases with but Q(2), too fast.