Elmar Biernat

Universidade Técnica de Lisboa, Portugal

Meson properties from two different covariant approaches

I consider two different manifestly covariant approaches to mesons, Point-Form Quantum Mechanics (PFQM) and the Covariant Spectator Theory (CST). In the first part of my seminar I present a Poincare-invariant coupled-channel approach based on PFQM to investigate the electromagnetic structure of pseudoscalar and vector mesons. We calculate the bound-state current from the 1-photon-exchange optical potential for electron-meson scattering. The problem of cluster separability will be addressed and its consequences on the bound-state current will be discussed. In the second part I consider a unified covariant model for all mesons formulated within the CST-framework, which incorporates both confinement and chiral symmetry breaking. A fully consistent formulation requires the calculation of the quark's self-interaction with the interaction kernel. To this end I analyze the analytic structure of the CST contribution to the self-energy amplitude for a simple \phi^2-\chi theory. Finally, I sketch how our model will be applied to the pion.

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