Dissertation/Thesis Abstract

Fermion masses and new symmetries beyond the Standard Model
by Grossmann, Benjamin Nathanial, Ph.D., Oklahoma State University, 2010, 103; 3443393
Abstract (Summary)

The Standard Model (SM) lacks a satisfactory explanation for the large hierarchy of the fermion masses. The use of extra symmetries is used to create a mechanism to explain this hierarchy.

An additional local U(1)S symmetry is appended to the SM along with an electroweak singlet Higgs boson that has a vacuum expectation value at the electroweak scale. Unlike many other models, the SM fields are neutral under this extra symmetry. Using a Froggatt-Nielsen type mechanism, the mass hierarchy is explained through the interaction of the SM quarks. They do not directly interact with each other, but with additional heavy vector-like quarks that have masses at the TeV scale.

How the Higgs singlet contributes to the generation of the mass hierarchy is generalized across a set of 24 model variation. Some of the phenomenology of Higgs interactions with SM fields by Higgs decays and flavor changing neutral currents are also explored.

The direct interaction of a heavy vector-like quark with a SM quark (the bottom quark) is also examined. The signal rates of this heavy vector-like quark and the SM background are calculated for the dominant signals at the high-energy hadron colliders, multilepton and multi-b-jet final states. For a wide range of masses, the signals are above the background at the LHC.

The neutrino masses are addressed by a different symmetry. Imposing a Z2 symmetry, the SM neutrinos have interactions with two new Higgs fields and heavy right-handed neutrinos with masses in electroweak scale. The smallness of the left-handed neutrino masses is the result of a combination of fine tuning between the two new Yukawa couplings and using the see-saw mechanism. The proposed scenario gives interesting new Higgs decay signals and can be tested at the LHC.

Indexing (document details)
Advisor: Nandi, Satyanarayan
Commitee: Babu, Kaladi S., Binegar, Birne, Perk, Jacques H. H.
School: Oklahoma State University
Department: Physics
School Location: United States -- Oklahoma
Source: DAI-B 72/04, Dissertation Abstracts International
Subjects: Theoretical physics, Particle physics
Keywords: Collider phenomenology, Fermions, Fine-tuning, Mass hierarchy, Standard Model, Vector-like quarks
Publication Number: 3443393
ISBN: 978-1-124-48320-7
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