Onium Masses with Three Flavors of Dynamical Quarks

We have greatly extended an earlier calculation of the charmonium spectrum on three flavor dynamical quark ensembles by using more recent ensembles generated by the MILC collaboration. The heavy quarks are treated using the Fermilab formulation. The charmonium state masses are in reasonable agreement with the observed spectrum; however, some of the spin splittings may still be too small.