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Accurate nucleon electromagnetic form factors from dispersively improved chiral effective field theory
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 GeV^2. Our parametrization provides proper
analyticity and theoretical uncertainty estimates and can be used for low-Q^2
FF studies and proton radius extraction.Comment: 5 pages, 3 figures, 2 table
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