Dispersion-theoretical analysis of the nucleon electromagnetic form factors: Inclusion of time-like data

We update a recent dispersion-theoretical fit to the nucleon electromagnetic form factors by including the existing data in the time-like region. We show that while the time-like data for the proton can be described consistently with the existing world space-like data, this is not the case for the neutron. Another measurement of the process e+e− → nn is called for. We furthermore sharpen the previous estimate of the separation between the perturbative and the non-perturbative regime, which is characterized by a scale parameter Λ2 ⋍ 10 GeV2.