Unitarity Constraints on effective interaction in $ÏN$ scattering
arXiv:hep-ph/0611325 · doi:10.1016/j.physletb.2007.03.052
Abstract
Positivity constraints are derived on pion-nucleon scattering amplitudes and their even-order derivatives inside the Mandelstam Triangle with the help of dispersion relations. Fairly interesting constraints are obtained on some of the low energy constants, by a combination of the chiral perturbation theory for heavy baryons and existing fitting results from available pion-nucleon phase shifts at intermediate energies.
version to appear in Phys. Lett. B. 6 pages