NPAC Technical Report SCCS-760
Radial Excitations in NRQCD
Simon Catterall, Frank Devlin, Ian Drummond, Ron Horgan
Submitted April 10 1996
Abstract
Following the Non-Relativistic QCD approach we use a gauge invariant
smearing method with factorization to measure the
excitation energies for a heavy $Q\bar{Q}$ system on a $24^3\times 48$
lattice at $\beta=6.2$. The results come from averaging over an ensemble of
60 QCD configurations. In order to enhance the signal from each configuration
we use wall sources for quark propagators. The quark Hamiltonian contains
only the simplest non-relativistic kinetic energy term.
insensitive to this variable though there are a slight trends with
increasing quark mass.
For an appropriate choice of UV cut-off ($a^{-1}=3.2$Gev)
the mass spectrum compares reasonably well with the experimental
values for the spin-averaged energy gaps of the $\Upsilon$ system.
We also present results for the $DE$ and $DT$ waves for the lowest bare
quark mass.
This encourages the idea that even with our simple quark Hamiltonian the
departure from rotational invariance is not great.