Heavy-quark spectroscopy for effective-action models

Results are reported for an application of the effective-action method to the computation of spectra for cc - , bb - , and tt - systems. The method determines static potentials from models for the vacuum dielectric permeability, of which two are considered: the leading-logarithm model and a hard-bag model. The spectra are then computed with standard nonrelativistic techniques. A new value of the leading-logarithm-model parameter κ is obtained from a fit to bb - data; it corresponds to a value of 161 MeV for ΛMS - , the scale mass of quantum chromodynamics (MS - denotes the modified minimal-subtraction scheme).