Abstract

We present a theoretical parametrization of the nucleon electromagnetic form factors (FFs) based on a combination of chiral effective field theory and dispersion analysis. The isovector spectral functions on the two-pion cut are computed using elastic unitarity, chiral pion-nucleon amplitudes, and timelike pion FF data. Higher-mass isovector and isoscalar $t$ -channel states are described by effective poles, whose strength is fixed by sum rules (charges, radii). Excellent agreement with the spacelike proton and neutron FF data is achieved up to $Q^{2}\sim 1$ GeV2. Our parametrization provides proper analyticity and theoretical uncertainty estimates and can be used for low- $Q^{2}$ FF studies and proton radius extraction.