Exploring chiral dynamics with low-energy electron- and positron-nucleon scattering

Abstract

Low-energy lepton-nucleon scattering probes various expressions of the long-distance dynamics in the baryon sector of QCD, governed by chiral symmetry breaking and the $\Delta$ resonance. We discuss some specific studies that could be performed with combined electron- and positron-nucleon scattering at lab energies $E_{e\pm} \lesssim$ 500 MeV. They include: (a) chiral dynamics in the low-$Q^2$ nucleon elastic form factors (peripheral charge and current densities); (b) two-photon exchange effects in the target normal single-spin asymmetry and beam charge asymmetry in elastic and inclusive scattering ($\Delta$ excitation); (c) nucleon generalized polarizabilities in virtual Compton scattering with beam charge asymmetry measurements.