| We study the mass difference between the spin singlet and spin triplet states of heavy quarkonium. The quarkonium meson is a non-relativistic quark-antiquark bound-state of quantum chromodynamics (QCD). We set up a matching procedure between the perturbative analysis of the short-distance interactions, and the nonperturbative lattice analysis of the long-distance effects. To this end, we calculate the part of the corresponding Wilson coefficient in the continuum QCD region, to first order in the strong coupling constant. We then improve upon the first order result by all-order resummation of the large logarithms of the lattice spacing. |
