UC San Diego

In this paper we consider the effects of top-quark compositeness on the electroweak parameters T^ and S^ and the ZbLb̄L coupling. We do so by using an effective field theory analysis to identify several promising patterns of mixing between standard-model-like and vector fermions, and then analyzing simple extensions of the standard model that realize those patterns. These models illustrate four ways in which an extended O(4) symmetry, which controls the size of radiative corrections to the observables discussed, may be broken. These models may also be viewed as highly deconstructed versions of five-dimensional gauge theories dual to various strongly interacting composite Higgs theories. We comment on how our results relate to extra-dimensional models previously considered, and we demonstrate that one pattern of O(4) breaking is phenomenologically favored. © 2011 American Physical Society.