Lattice QCD determination of weak decays of B mesons

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Harrison, Judd Gavin Ivo Henry 

This thesis uses a variety of numerical and statistical techniques to perform high precision calculations in high energy physics using quantum field theory. It introduces the experimental motivation for the calculation of B meson form factors and includes a discussion of previous work. It then describes the modern theoretical framework describing these phenomena, outlining quantum chromodynamics and electroweak theory, and then illustrating the procedure of gauge fixing, the quantum effective action and background field gauge which is required for subsequent perturbative work. Details of the basic methodology of lattice quantum field theory are given as well as the specific formulation of the relativistic theory and nonrelativistic approximations used in this work to describe quantum chromodynamics. A comprehensive calculation of the zero recoil B to D* form factor is then presented, using state of the art lattice techniques with relativistic charm sea quarks and light sea quarks with correct physical masses, leading to a discussion of the dominant sources of uncertainty and possible resolutions of experimental tensions. Also included is preliminary work towards the full calculation of nonzero recoil matrix elements, with the aim of outlining possible future work. Finally, this thesis presents the computation of parameters correcting for radiative one loop phenomena and corrections to the kinetic coupling parameters in nonrelativistic quantum chromodynamics in order to achieve a desirable level of precision in future calculations. This is done using Monte-Carlo integration to evaluate integrals from diagrams generated using automated lattice perturbation theory in background field gauge in order to match the coefficients of the effective action between the lattice and the continuum.

Wingate, Matthew
Lattice QCD, Quantum Chromodynamics, Quantum Field Theory, B mesons
Doctor of Philosophy (PhD)
Awarding Institution
University of Cambridge