Technicolor and new matter generations

Abstract

This work consists of an overview part and three research papers. The subject of this work is a class of models for dynamical electroweak symmetry breaking, and new generations of fermionic matter. An introductory overview of the standard model of electroweak interactions is given, as well as an overview of some of the recent developments in the field of walking technicolor models. We study some recently proposed models for dynamical electroweak symmetry breaking, namely the minimal walking technicolor (MWT) and next to minimal walking technicolor (NMWT) model. We show that, as a result of cancellation of the global and gauge anomalies associated with the technicolor sector, a non sequential SM-like matter generation may naturally arise. We study the effects of this new matter generation on electroweak and flavor observables and derive constraints for the masses of the new fermions. We show that the new fermions may have a significant impact on the physics of the composite Higgs boson of the technicolor theory. We present the resulting decay branching ratios and production cross sections of the composite Higgs boson. We also find that the fermions themselves should be visible in the LHC experiment, and outline basic search strategies. We construct a model framework for the origin of fermion masses, in which a technicolor sector is accompanied by a scalar boson. In this bottom-up-approach the scalar represents the low energy spectrum of the yet unkown full gauge theory responsible for fermion masses. We construct a low energy effective Lagrangian and use electroweak and flavor precision observables, as well as direct detection limits, to constrain the parameters of the model. We find that the low energy particle spectrum of the model consists of one light and one heavy Higgs-like scalar, accompanied by three massive technipions. We find that all of the models studied in this work are viable in the light of all existing electroweak and flavor precision data. The LHC experiment will be able to give crucial information on the subject, and possibly confirm or rule out some of the models studied in this work.