The Role of the Top Quark in Theories of Dynamical Electroweak Symmetry Breaking

Available from UMI in association with The British Library. We study various models which attempt to break electroweak symmetry dynamically and simultaneously give a realistic fermion spectrum. A truncation of the Schwinger -Dyson equations of the field theory called the ladder Gap Equation is used as our basic calculational tool. Throughout we concentrate on whether these models can predict a top quark in the range expected from the limits of delta p. We find a top quark mass larger than 100GeV can be obtained in these models but that none of the models considered is completely satisfactory from a theoretical viewpoint. We first consider the tope mode standard model in which the top quark plays a central role in breaking electroweak symmetry. We study the prediction of the model for the mass of the top quark as well as a fine tuning problem associated with the model. We proceed to consider an extension of the model in which higher dimensional operators are included. Next we consider a technicolor model where the interactions of technifermions and top quarks are both important for breaking electroweak symmetries and providing the correct fermion spectrum. Finally we consider an extended technicolor model and study in detail the mass spectrum of fermions and technifermions that arises.