Applying the variational method, the spinless reduced Bethe-Salpeter (RBS) equation is solved for the mesonic systems, and the mass spectra are obtained. The method is applied to the Hamiltonian with the Gaussian and hydrogen-type trial wave functions, and different potential models are examined. The results for the different potentials are in challenge in light mesons, while they are consisten...

Using the local flavor SU(4) gauge invariance in the limit of vanishing vector meson masses, we extend our previous study of charm meson scattering cross sections by pion and rho meson, which is based only on the pseudoscalarpseudoscalar-vector meson couplings, to include also contributions from the couplings among three vector mesons and among four particles. We find that diagrams with light m...

We review the theory of hadronic atoms in QCD + QED, based on a non–relativistic effective Lagrangian framework. We first provide an introduction to the theory, and then describe several applications: meson– meson, meson–nucleon atoms and meson–deuteron compounds. Finally, we compare the quantum field theory framework used here with the traditional approach, which is based on quantum–mechanical...