Pion-nucleon scattering inside the Mandelstam triangle

We study the third order pion-nucleon scattering amplitude obtained from he avy baryon chiral perturbation theory inside the Mandelstam triangle. We re construct the pion-nucleon amplitude in the unphysical region by use of dis persion relations and determine the pertinent low-energy constants by a fit to this amplitude. A detailed comparison with values obtained from phase s hift analysis is given. Our analysis leads to a pion-nucleon sigma-term of sigma(0) = 40 MeV based on the Karlsruhe partial wave analysis. We have rep eated the same procedure: using the latest solution of the VPI group and fi nd a much larger value for sigma(0). (C) 2000 Elsevier Science B.V. All rig hts reserved.