Scaling of the Upsilon Spectrum in Lattice NRQCD
  We present results for the spectrum of b-bbar bound states in the quenched approximation for three different values of the lattice spacing, in the range 0.05fm to 0.15fm. We find our results for spin-independent splittings in physical units to be independent of the lattice spacing, indicating the absence of systematic errors from discretisation effects. Spin-dependent splittings are more sensitive to the lattice spacing and higher order corrections to the action; we discuss the size of these effects and what can be done to arrive at a physical result. 
C. T. H. Davies, K. Hornbostel, G. P. Lepage, A. Lidsey, P. McCallum,   J. Shigemitsu, J. Sloan