The πN partial waves at low energies and in the unphysical region

Abstract

The real parts of theπN partial wave amplitudesf ⁽⁻⁾_l± have been calculated from fixed-t dispersion relations, using phase shifts up to 2 GeV and the reggeizedp-exchange model at higher energies. The comparison with Ref ⁽⁻⁾_l± as calculated directly from phase shifts shows to what extent the input is consistent with the fixed-t relation. The result is also of interest for the test of simple models, in particular for the comparison with predictions from current algebra. — A new evaluation of the partial wave dispersion relation forf ⁽⁻⁾₀₊ is presented. Combined with the first method it shows that the determination of thep-coupling parameter is based on an assumption which is difficult to justify.