Studies of Dynamical Electroweak Symmetry Breaking.

An important outstanding problem of high energy physics is the question of what breaks the electroweak symmetry. One possibility is that it is broken dynamically. There may be new dynamics, analogous to quantum chromodynamics, called technicolor (TC), which would become strong at around a TeV and cause the condensation of technifermion pairs. These bilinear fermion condensates would then break the electroweak symmetry and give masses to the W and Z gauge bosons. A TC model also must explain the spectrum of SM fermion masses and so must be embedded into a larger theory called extended technicolor (ETC), which communicates the breaking to the standard-model fermions and gives them mass. The research of this thesis focuses on the analysis of TC/ETC models. In one work we analyze constraints on a class of ETC models from flavor-changing neutral current processes. This involves a detailed study of a model with a high degree of ultraviolet completeness for the ETC dynamics. In another work we note the momentum dependence of fermion masses produced dynamically and derive and apply a new test for these models. We also construct a TC model that produces an optimally small correction to precision electroweak quantities and still has the desired property of a large but slowly running gauge coupling. Finally, we construct an explicit ultraviolet-complete ETC model that appropriately splits the masses mt and mb without excessive contributions to the rho parameter or to flavor-changing neutral current processes.