Dynamical Electroweak Symmetry Breaking On The Lattice

The LHC is expected to fid new physics beyond the Standard Model (BSM). Technicolor models are a class of BSM models which involve a new strongly interacting sector responsible for electroweak symmetry breaking (EWSB). The phenomenological viability of these models depends on features such as the existence of an infrared fixed point (IRFP) at strong coupling, and the size of the mass anomalous dimension at this fixed point. As these features are at strong coupling they are not accessible to perturbative methods, and so need to be investigated non-perturbatively using lattice methods. In this thesis, two candidate Technicolor theories are investigated using two independent and complementary lattice methods, the Schrodinger Functional (SF) and the Monte Carlo Renormalisation Group (MCRG), to measure the running of the coupling and the anomalous mass dimension in these theories.

This volume contains the talks given at the above workshop which was devoted to discussing the newest developments in various models of electroweak symmetry breaking forming the basis of modern particle physics. It includes various aspects of Higgs physics and condensate models embodying dynamical symmetry breaking.

Abstract: In this dissertation I use lattice gauge theory to study models of electroweak symmetry breaking that involve new strong dynamics. Electroweak symmetry breaking (EWSB) is the process by which elementary particles acquire mass. First proposed in the 1960s, this process has been clearly established by experiments, and can now be considered a law of nature. However, the physics underlying EWSB is still unknown, and understanding it remains a central challenge in particle physics today. A natural possibility is that EWSB is driven by the dynamics of some new, strongly-interacting force. Strong interactions invalidate the standard analytical approach of perturbation theory, making these models difficult to study. Lattice gauge theory is the premier method for obtaining quantitatively-reliable, nonperturbative predictions from strongly-interacting theories. In this approach, we replace spacetime by a regular, finite grid of discrete sites connected by links. The fields and interactions described by the theory are likewise discretized, and defined on the lattice so that we recover the original theory in continuous spacetime on an infinitely large lattice with sites infinitesimally close together. The finite number of degrees of freedom in the discretized system lets us simulate the lattice theory using high-performance computing. Lattice gauge theory has long been applied to quantum chromodynamics, the theory of strong nuclear interactions. Using lattice gauge theory to study dynamical EWSB, as I do in this dissertation, is a new and exciting application of these methods. Of particular interest is non-perturbative lattice calculation of the electroweak S parameter. Experimentally S [approximate] -0.15(10), which tightly constrains dynamical EWSB. On the lattice, I extract S from the momentum-dependence of vector and axial-vector current correlators. I created and applied computer programs to calculate these correlators and analyze them to determine S . I also calculated the masses and other properties of the new particles predicted by these theories. I find S [Special characters omitted.] 0.1 in the specific theories I study. Although this result still disagrees with experiment, it is much closer to the experimental value than is the conventional wisdom S [Special characters omitted.] 0.3. These results encourage further lattice studies to search for experimentally viable strongly-interacting theories of EWSB.

The papers presented here focus on new developments in both theoretical and phenomenological aspects of standard theory, with an emphasis on understanding of the mechanism of electroweak symmetry breaking. This workshop covers the formal aspects and the related new models of electroweak symmetry breaking and the present status of the Standard Model.

This is the first systematic volume which presents a detailed introduction to every facet of the modern version of Dynamical Symmetry Breaking which has been rapidly developed in recent years. Most of the lectures are given by pioneers in this new field and are geared mainly to the level of second year graduate students.

The phenomenon of dynamical symmetry breaking (DSB) in quantum field theory is discussed in a detailed and comprehensive way. The deep connection between this phenomenon in condensed matter physics and particle physics is emphasized. The realizations of DSB in such realistic theories as quantum chromodynamics and electroweak theory are considered. Issues intimately connected with DSB such as critical phenomenona and effective lagrangian approach are also discussed.

The aim of the book is to familiarize the new generation of PhD students and postdoctoral fellows with the principles and methods of modern lattice field theory, which aims to resolve fundamental, non-perturbative questions about QCD without uncontrolled approximations.