Note on the!so-Vector Part of the Nucleon Electromagnetic Form Factors

The iso-vector part of the nucleon electromagnetic form factors are reinvestigated in order to study the following properties: the difference between the dispersion relations for the Dirac and the Sachs form factors, the asymptotic behaviours of these form factors in large momentum transfer regions, and the stability of results on the variation of parameters which have been predetermined. In the momentum transfer region O>t>-1 (Gev /c) 2, we find an excellent agreeement between experiment and dispersion relations both for the Dirac and the Sachs form factors, for rather widely different values of the p-meson width and the cutoff momentum. For the high momentum transfer region it is shown that the Sachs conditions can be satisfied by adding pole terms with the mass of about 1.6 Gev. By this modification we also get a result consistent with the pp->ee experiment for the time-like momentum transfer region