Effective Field Theory of the PionNucleonInteraction.pdfVIP

Effective Field Theory of the Pion-Nucleon-Interaction∗ H. Leutwyler Institute for Theoretical Physics, University of Bern, Sidlerstr. 5, CH-3012 Bern, Switzerland Abstract In the first part of the talk, I discussed the nature of the effective theory that describes the properties of the pion-nucleon-interaction at low energies, using the static model as a starting point. In the second part, I then pointed out that the infrared singularities occurring in the πN scattering amplitude are stronger and of a 0 more complex structure than those encountered in ππ scattering. A formulation of the 0 effective theory that properly accounts for these was described and the results obtained 0 2 thereby were illustrated with a few examples. In the following, I restrict myself to a discussion of some qualitative aspects of this work. g u A INTRODUCTION 2 The static model represents a forerunner of the effective theories of the pion-nucleon 1 interaction used today. In this model, the kinetic energy of the nucleon is neglected: The nucleon is described as a fixed source that only carries spin and isospin degrees of freedom. 1 For an excellent review of the model and its application to several processes of interest, I v refer to the book of Henley and Thirring[1]. 3 2 The systematic formulation of the effective theory relies on an expansion of the effective 1 Lagrangian in powers of derivatives and quark