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. © 1984 The American Physical Society.

We have formulated a relativistic two-body equation for quark-antiquark bound states using the expansion in intermediate states. We have used the asymptotically free QCD gluon exchange with either a scalar or equal vector and scalar linear potential. Using these we have fitted the upsilon, charmonium, D, F, ss, s-u, d and u, d quark mesons for the rho and above. We have also calculated relativistically their widths, singlet-triplet and P-state splittings. © 1984.