Isospin-breaking corrections to the pion–nucleon scattering lengths
نویسندگان
چکیده
We analyze isospin breaking through quark mass differences and virtual photons in the pion– nucleon scattering lengths in all physical channels in the framework of covariant baryon chiral perturbation theory. The so-called triangle relation is found to be violated by about 1.5 %. We encounter a substantial isospin-breaking correction to neutral-pion–nucleon scattering beyond Weinberg’s prediction due to a cusp effect. Finally, the application to hadronic atoms is briefly discussed.
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