Non-relativistic QCD for heavy quark systems

Abstract We employ a non-relativistic version of QCD (NRQCD) to study heavy q q bound states in the lowest approximation without fine structure. We use gluon configurations on a 63×48 lattice at β=6.2 from the UKQCD Collaboration. For a bare quark mass near that of the b-quark (Ma=1.6) we obtain the bound state masses for the S-, P- and both types of D-waves. We also detect signals for two types of hybriges ( q q g states). The results are sufficiently accurate to confirm that the values of the D-wave mass from both D-waves coincide thus indicating that the cubical invariance of the lattice is restored to full rotational invariance to a good approximation. We also study S- and P-wave masses for values of the range of bare quark mass Ma=1.0, 1.3, 1.6 and 1.9. The results confirm the idea that the S/P-splitting is relatively insensitive to the value of the bare quark mass.