Isospin violation in low-energy pion-nucleon scattering revisited

Understand

We calculate isospin breaking in pion-nucleon scattering in the threshold region in the framework of covariant baryon chiral perturbation theory.

• All effects due to quark mass differences as well as real and virtual photons are consistently included.
• As an application, we discuss the energy dependence of the triangle relation that connects elastic scattering on the proton pi+- p --> pi+- p with the charge exchange reaction pi- p --> pi0 n.