Heavy-quark--antiquark potential in the MIT bag model

The MIT bag model for a meson composed of a heavy quark and a heavy antiquark is solved using the Born-Oppenheimer approximation. For fixed qq-bar separations the color-electric fields and bag shapes are determined by solving numerically the Yang-Mills equations with bag boundary conditions to lowest order in the quark-gluon coupling constant. Spin effects are not included. The resulting bag energy is used as a potential energy in the Schroedinger equation for the relative motion of the quarks. Good agreement with the experimental psi and UPSILON spectra and leptonic decay widths is found. When the same potential is applied to strange-quark systems, a consistent picture of the masses of the phi and F* mesons emerges. The relation between spectroscopy and the variation of the coupling constant with distance is explored