Isospin Breaking in Low-Energy Pion-Nucleon Scattering

We have analyzed low-energy pion-nucleon data for isospin invariance by comparing charge-exchange amplitudes derived from charge-exchange data with those predicted from recent ${\pi }^{\pm }p$ elastic data through the application of isospin invariance. A discrepancy of the order of 7% is observed beyond the contributions of the ${\pi }^{\pm }p$ Coulomb interaction and the hadronic mass differences.