S and P - wave heavy - light mesons in lattice NRQCD

The mass spectrum of S and P-wave mesons containing a single heavy quark is computed in the quenched approximation, using NRQCD up to third order in the inverse heavy quark mass expansion. Previous results found the expansion to break down near the charm quark mass for the S-wave spin splitting. The present work considers variations such as anisotropic lattices, Landau link tadpole improvement, and a highly-improved light quark action, but finds that these modifications do not enhance convergence for charmed mesons. The expansion is reasonable for bottom mesons, and is also found to be wellbehaved for the P-wave charmed masses. The relative orderings among Pwave charmed and bottom mesons, and the sizes of the mass splittings, are discussed in light of experimental data and existing calculations. Typeset using REVTEX