Scaling of the Υ spectrum in lattice nonrelativistic QCD

We present results for the spectrum of $b\overline{b}$ 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.