Nucleon form factors in dispersively improved Chiral Effective Field Theory II: Electromagnetic form factors

Understand

We study the nucleon electromagnetic form factors (EM FFs) using a recently developed method combining Chiral Effective Field Theory ($\chi$EFT) and dispersion analysis.

• The spectral functions on the two-pion cut at $t > 4 M_\pi^2$ are constructed using the elastic unitarity relation and an $N/D$ representation.
• $\chi$EFT is used to calculate the real functions $J_\pm^1 (t) = f_\pm^1(t)/F_\pi(t)$ (ratios of the complex $\pi\pi \rightarrow N \bar N$ partial-wave amplitudes and the timelike pion FF), which are free of $\pi\pi$ rescattering.
• Rescattering effects are included through the empirical timelike pion FF $|F_\pi(t)|^2$.