### 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.

Back to the Theory seminar page.