Quantum effective field theories in heavy quark physics and phase transitions in cosmology

Citation

Lee, Clarence L. Y. (1994) Quantum effective field theories in heavy quark physics and phase transitions in cosmology. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/tr7n-vw39. https://resolver.caltech.edu/CaltechTHESIS:04182012-104107815

Abstract

This thesis is concerned with aspects of quantum effective field theories, effective actions, and their applications. New spin-flavor symmetries of the strong interactions, which arise in the limit of very large quark masses, can be incorporated into a heavy quark effective field theory (HQEFT). A general method for deriving the effective Lagrangian of this theory to any order in 1/m_Q (where m_Q is the heavy quark mass) is developed; it is used to calculate terms up to order 1/m^3_Q. The renormalization of terms in the Lagrangian to order 1/m^2_Q is performed. Such operators break these new symmetries and consequently are important corrections to the leading-order predictions. HQEFT can be combined with chiral perturbation theory into a heavy meson chiral perturbation theory (HMChPT) which describes the low-momentum interactions of hadrons containing a heavy quark with pseudo-Goldstone bosons. HMChPT is used to investigate the semi-leptonic four-body decay of B and D mesons into final states with at least one Goldstone boson. Such processes may be utilized to test the above heavy quark symmetries. The remainder of this dissertation deals with the evaluation of effective actions and their implications. A method to efficiently compute the one-loop effective action at zero and finite temperatures is elucidated. In a first order cosmological phase transition, the decay rate and the temperature at which it occurs depends on the free energy of a critical bubble configuration. Since this free energy is related to the effective action but is usually approximated with an effective potential, the calculational method developed above is used to study the validity of of this approximation. The corrections are found to be important for quantitative work.

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