RELATIVISTIC DESCRIPTION OF QUARK-ANTIQUARK BOUND-STATES .2. SPIN-DEPENDENT TREATMENT

We present the results of a study of light- and heavy-quark-antiquark bound states in the context of the reduced Bethe-Salpeter equation, including the full spin dependence. We obtain good fits to the observed spin splittings in the bb» and cc» systems using a short-distance single-gluon-exchange interaction, and a long-distance scalar confining interaction. However, we cannot obtain satisfactory fits to the centers of gravity of the bb» and cc» spin multiplets at the same time, and the splittings calculated for qQ» mesons containing the lighter quarks are very poor. The difficulty appears to be intrinsic to the reduced Salpeter equation for reasons which we discuss. © 1990 The American Physical Society.