Updated description of quarkonium by power-law potentials

The spectra and decay rates of charmonium (cc̄) and bottomonium (bb̄) levels are well described, for the most part, by a power-law potential V(r)=λ(r^α-1)α+const, where α0. The results of an up-to-date fit to the data on spin-averaged levels are presented. A fit to levels alone favors α=-0.045 and gives very little preference for quark masses, while inclusion of leptonic width data leads to α=-0.14 and a b-quark mass in the vicinity of 5 GeV. A fit to the known electric dipole transitions in bb̄ systems favors a slightly smaller b-quark mass, but with large errors.