DISPERSION-THEORETICAL ANALYSIS OF THE NUCLEON ELECTROMAGNETIC FORM-FACTORS

Dispersion relations allow for a coherent description of the nucleon e lectromagnetic form factors measured over a large range of momentum tr ansfer, Q(2) similar or equal to 0-35 GeV2. Including constraints from unitarity and perturbative QCD, we present a novel parametrisation of the absorptive parts of the various isoscalar and isovector nucleon f orm factors. Using the current world data, we obtain results for the e lectromagnetic form factors, nucleon radii and meson couplings. We str ess the importance of measurements at large momentum transfer to test the predictions of perturbative QCD.