Relativistic treatment of quark-antiquark spectra in quantum chromodynamics

A fully relativistic bound-state equation is used to study the spectra (and leptonic widths) of charmonium, $b$-quarkonium, $D$ mesons, $F$ mesons, $B$ mesons, and mesons composed of light quarks. The short-distance behavior of the interaction is that of asymptotically free QCD, while the largedistance interaction is a linear confining one whose Lorentz nature is either pure scalar or an equal mixture of vector and scalar. Multiquark states are accounted for in an approximate manner. An interesting dependence of the quark masses on the Lorentz nature of the long-distance interaction and on the overall mass scale of the system is obtained.