Qq-bar bound states in the Bethe-Salpeter formalism.

Abstract

We solve the Bethe-Salpeter equation in order to calculate the spectrum of pseudoscalar, vector, and scalar meson bound states for light as well as heavy quarks, extending our previous calculation of pseudoscalar mesons. The fermion propagators appearing in the equation are obtained by solving the Schwinger-Dyson equation consistently with the Bethe-Salpeter equation, a procedure necessary for demonstrating the Goldstone nature of the pion in the chiral limit. We probe in our calculations a model for the gluon propagator which leads to the expected three-dimensional potential in configuration space, while maintaining its known ultraviolet behavior. Our procedure provides a unified description of both the light and heavy mesons and obeys known relations derived on the basis of current algebra for light quarks and a nonrelativistic analysis for heavy quarks. The results are in good agreement with experiment for the mass spectrum and for the pseudoscalar mesons' decay constants. We also calculate electromagnetic and isospin mass splittings for these mesons.