EXCITED-STATES FOR HEAVY-QUARK SYSTEMS IN NRQCD

Following the Non-Relativistic QCD approach we use a gauge invariant smearing method with factorization to measure the excitation energies for a heavy QQBAR system on a 24(3) x 48 lattice at beta = 6.2. The quark Hamiltonian contains only the simplest non-relativistic kinetic energy term. The mass splittings are not sensitive to the quark mass. For an appropriate choice of UV cut-off (a-1 = 3.2Gev) the mass spectrum compares reasonably well with the experimental values for the spin-averaged energy gaps of the UPSILON system. Our results for the DE and DT waves at the lowest bare quark mass exhibit degeneracy between the two D-waves.