Quark mass hierarchy and dynamical symmetry breaking
Abstract
The origin of fermion masses is one of the current outstanding problems of particle physics. The concepts of gauge invariance and spontaneous symmetry breaking, or Higgs Mechanism, have been very successful in providing masses for the Standard Model (SM) gauge bosons. The SM, however, assumes the existence of a scalar field, the Higgs field whose vacuum expectation value breaks electroweak symmetry, and in the process giving the W and Z bosons their mass. While there are some questions as to whether a scalar field is actually responsible for EWSB, it is possible that other mechanisms maybe at work, alternative theories include Technicolor (TC) and Extended Technicolor (ETC). This thesis consists of two parts: In part A the fermion mass terms as they appear in the SM are examined. In particular, the fermion mass matrices are studied using the Triangular Matrices technique. The mass matrices are classified by their texture zero pattern, and the corresponding CKM matrices are calculated, and compared with experimental values. It is found that only four possible textures are compatible with experiment. Also, the application of one of the textures to Flavor Changing Neutral Currents (FCNC) is discussed. In part B, the possible origin of the fermion masses is briefly discussed in the context of TC and ETC theories, and a few of the shortcomings of these models are outlined. A new model for the generation of fermion masses is presented. This model draws heavily on the success of the SM, but differs in the absence of a scalar field. It also differs from other ETC models by introducing a different type of gauge group, the ``composite gauge group'', and also by introducing a charged boson exchange. It is found that the present fermion masses can be generated as condensates from ETC fermions, where, the observed hierarchy is related to the CKM matrix. It is also found that the ETC confinement scale must be of the order of 54 times the exchanged ETC boson mass in order to observe the ETC quarks in the 1-2 Tev scale. Other effects such FCNC's are also discussed. It is shown that FCNC's are suppressed by a GIM mechanism as in the SM.
- Publication:
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Ph.D. Thesis
- Pub Date:
- August 2001
- Bibcode:
- 2001PhDT........28V
- Keywords:
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- Physics: Elementary Particles and High Energy