Unquenched Lattice Upsilon Spectroscopy

Marcantonio, Laurence Mark (2001) Unquenched Lattice Upsilon Spectroscopy. PhD thesis, University of Glasgow.

Abstract

A non-relativistic effective theory of QCD (NRQCD) is used in calculations of the upsilon spectrum. Simultaneous multi-correlation fitting routines are used to yield lattice channel energies and amplitudes. The lattice configurations used were both dynamical, with two flavours of sea quarks included in the action; and quenched, with no sea quarks. These configurations were generated by the UKQCD collaboration. The dynamical configurations used were "matched", having the same lattice spacing, but differing in the sea quark mass. Thus, it was possible to analyse trends of observables with sea quark mass, in the certainty that the trend isn't partially due to varying lattice spacing. The lattice spacing used for spectroscopy was derived from the lattice 11P1 -13S1 splitting. On each set of configurations two lattice bare b quark masses were used, giving kinetic masses bracketing the physical Upsilon mass. The only quantity showing a strong dependence on these masses was the hyperfine splitting, so it was interpolated to the real T mass. The radial and orbital splittings gave good agreement with experiment. The hyperfine splitting results showed a clear signal for unquenching and the dynamical hyperfine splitting results were extrapolated to a physical sea quark mass. This result, combined with the quenched result yielded a value for the hyperfine splitting at nf = 3, predicting an rib mass of 9.517(4) GeV. The NRQCD technique for obtaining a value of the strong coupling constant in the MS scheme was followed. Using quenched and dynamical results a value was extrapolated to nf = 3. Employing a three loop beta function to run the coupling, with suitable matching conditions at heavy quark thresholds, the final result was obtained for nf = 5 at a scale equal to the Z boson mass. This result was alpha(5)/MS(Mz)=0.110(4). Two methods for finding the mass of the b quark in the MS scheme were employed. The results of both methods agree within error but the errors were too large to see any clear signal of unquenching in mb. The best result obtained was 4.42(33) GeV.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Adviser: Christine Davies
• Keywords: Theoretical physics
• Date of Award: 2001
• Depositing User: Enlighten Team
• Unique ID: glathesis:2001-76001
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 19 Dec 2019 09:15
• Last Modified: 19 Dec 2019 09:15
• URI: https://theses.gla.ac.uk/id/eprint/76001