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HK: Physik der Hadronen und Kerne

HK 32: Theory V

HK 32.3: Group Report

Wednesday, March 10, 2004, 15:00–15:30, D

The structure of the nucleon in relativistic baryon chiral perturbation theory — •Stefan Scherer, Thomas Fuchs, Matthias R. Schindler, and Jambul Gegelia — Institut für Kernphysik, Johannes Gutenberg-Universität, Mainz

The implementation of a successful effective field theory program requires two main ingredients, namely: (a) a knowledge of the most general effective Lagrangian and (b) an expansion scheme for observables in terms of a consistent power counting method. We discuss a renormalization scheme for manifestly Lorentz-invariant baryon chiral perturbation theory which provides a simple and consistent power counting for renormalized diagrams. The method involves finite subtractions of dimensionally regularized diagrams beyond the standard modified minimal subtraction scheme of chiral perturbation theory to remove contributions violating the power counting. This is achieved by a suitable renormalization of the parameters of the most general effective Lagrangian. As applications we discuss the mass of the nucleon, the σ term, and the scalar and electromagnetic form factors. Our approach may be used in an iterative procedure to renormalize higher-order loop diagrams and also allows for implementing a consistent power counting when vector (and axial-vector) mesons are explicitly included.