DESCRIPTION OF RELATIVISTIC HEAVY-LIGHT Q UARK-ANTIQUARK SYSTEMS VIA DIRAC-EQUATION

Starting from the QCD Lagrangian and taking into account both perturba tive and nonperturbative effects, we use the method of vacuum correlat ors to derive the Dirac equation (rigorously for the Coulomb interacti on and heuristically for the confining potential) for a system consist ing of a light quark and heavy antiquark. As a result the confining po tential is a Lorentz scalar, and the Coulomb part is the fourth compon ent of a 4-vector. The energy spectrum of the Dirac equation is consid ered for these potentials. Numerical calculations of energy eigenvalue s E = E(nkappa) are performed, and some exact solutions of the Dirac e quation in the case E = 0 are found. An effective-potential method con venient for qualitative study of the solution of the Dirac equation is developed. The connection with experimental spectra of D- and B-meson s is briefly discussed.