Upsilon Spectroscopy Using Lattice QCD

[摘要] The non-relativistic QCD theory developed by the NRQCD collaboration is employed in simulations reproducing the upsilon spectrum. Correlations are analysed using multi-correlation fitting routines yielding energies and amplitudes. Good reproduction of the experimental upsilon spectrum is found with statistical errors comparable with systematic errors. The effects of three such systematic errors, lattice spacing, truncation of the relativistic expansion and quenching, are investigated. Radial and orbital splittings are found to have lattice spacing errors and truncation errors that are much smaller than statistical errors. These splittings give good to excellent agreement with experiment on the removal of quenching errors. Spin splittings and the wavefunction at the origin are found to have large lattice spacing, truncation and radiative correction errors which are of the order of 10%, comparable with statistical errors. These quantities give reasonable agreement with experiment on the removal of quenching errors and a prediction for the S state hyperfine splitting of 41(6) MeV is obtained. The method developed by the NRQCD collaboration to obtain the strong coupling constant in the MS scheme at the Z0 mass is followed with lattice spacings determined from the upsilon radial and orbital splittings used to scale the coupling values. A best value of 0.1171(23) was obtained for this coupling. Sources of systematic error affecting this value are investigated and are found to be at the few percent level.

[发布机构] University:University of Glasgow

[关键词] Theoretical physics