Heavy quarkonia at high temperature

We present results of the first application of non-relativistic lattice QCD to the study of heavy quarkonia at finite temperature. The aim is to calculate the dependence of the masses of these bound states on temperature from first principles. Our method combines non-relativistic QCD with an improved gluonic action on anisotropic lattices. The efficiency of the approach is demonstrated by the first non-perturbative calculation of the temperature dependence of low-lying quarkonium "pole" masses. For hypothetical ground state meson masses in the region between charmonium and bottomonium we find only very little variation up to our highest temperature which corresponds to T≈1.2 Tc while first excited states indicate a large mass shift.