Scaling of the Υ spectrum in lattice nonrelativistic QCD

We present results for the spectrum of bb̄ bound states in the quenched approximation for three different values of the lattice spacing, in the range 0.05 fm to 0.15 fm. 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 discretization 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.