We suggest a simple phenomenological parametrization for all three deuteron electromagnetic form factors, and show that a good fit on the available data, with a minimal number of parameters, can be obtained. The present description of the deuteron electromagnetic structure is based on two components with different radii, one corresponding to two nucleons separated by ≃2 fm, and a standard isoscalar contribution, saturated by ω and φ mesons, only.

A system of linear homogeneous algebraic equations for coupling constant ratios of vector-mesons to hadrons is derived by imposing an assumed asymptotic behaviour upon the VMD pole parametrization of an hadron electromagnetic form factor. A similar system of equations with a simpler structure of coefficients, taken as even powers of vector-meson masses, is derived by means of integral superconvergent sum rules for the imaginary part of the considered form factor using its appropriate δ-function approximation. Although both systems have been derived starting from different properties of the electromagnetic form factor and they look each in its own way, it is shown explicitly that they are fully equivalent.

The axial form factor of the nucleon is studied in a two-component model consisting of a threequark intrinsic structure surrounded by a meson cloud. The experimental data in the space-like region are well reproduced with a minimal number of parameters. The results are similar to those obtained from a dipole fit for 0 < Q 2 < 1 GeV 2 , but outside this region there are important deviations from the dipole parametrization. Finally, the theoretical formula for the axial form factor is extrapolated by analytic continuation to the time-like region, thus providing the first predictions in this kinematical region which is of interest for present and future colliders.