SPIN-DEPENDENT INTERACTIONS IN HEAVY QUARK SYSTEMS

Some features of spin-dependent forces in heavy quark-antiquark systems are studied in QCD perturbation theory. The spin-dependent potentials in these systems are shown to depend non-trivially on the heavy quark mass. This dependence arises from processes taking place at distances on the order of the quark Compton wavelength. Using these results, the limitations of schemes which have been introduced recently to compute spin-dependent forces due to instantons are illustrated. © 1979.