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Higgs coupling characteristics of the phenomenological study

Author: LiuZuoZuo
Tutor: MaWenZuo
School: University of Science and Technology of China
Course: Particle Physics and Nuclear Physics
Keywords: University of Science and Technology of China Gauge bosons The standard model Radiative correction Doctoral Dissertation Fermions Quark New physical Generating process Supersymmetric
CLC: O572.23
Type: PhD thesis
Year: 2007
Downloads: 141
Quote: 0
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Abstract


The origin of the electroweak symmetry breaking is the most important open question of contemporary particle physics which was first answered in 1964 by Higgs, Kibble, Guralnik, Hagen, Englert, and Brout. The mechanism of spontaneous symmetry breaking they proposed known as Higgs mechanism gives mass to all elementary particles in particle physics. The unification of the electromagnetic and weak interactions into a single electroweak force - a feat that earned Salam, Weinberg and Sheldon Glashow the Nobel prize in 1979 - named as Standard Model which contains 12 spin-1/2 fermions (6 quarks and 6 leptons), 4 spin-1 ’gauge’ bosons and a spin-0 Higgs boson.One of the major motivations for physics beyond the Standard Model (SM) is to resolve the hierarchy and fine-tuning problems between the electroweak scale and the Planck scale. The cancellations of the quadratic divergence in the littlest Higgs model occur between particles with the same statistics: divergences due to gauge bosons are canceled by new gauge bosons and similarly for the heavy quarks. One of the most important task of present and future experiments is to search for Higgs boson and investigate its properties. Studying the properties of the Higgs potential will reveal details of mass-generation mechanism in spontaneously broken gauge theories, which can be obtained through measuring the Higgs boson self-interactions. Theoretically, the study of top quark rare decay channels can be used as a tool in searching for new physics. The top quark due to its large mass, is very sensitive to new physics and its short lifetime makes the top quark decays before binding into hadrons with other lighter quarks. The Flavor Changing Neutral Gurrent(FCNC) decay of top quark into a charm quark and a neutral Higgs boson t→cH0 is a content of top physics, can present some important information about new physics.Supersymmetric theories introduce an extended space-time symmetry and quadrat-ically divergent quantum corrections are canceled due to the symmetry between the bosonic and fermionic partners. In both theories of the SM and the MSSM the Higgs mechanism predicts the Yukawa coupling. Because of the heavy top-quark mass, the couplingλh0tt is the strongest one among all the Higgs-fermion-antifermion couplings, and the cross section of the tth0 associated production is dominated by the amplitudes describing Higgs boson radiation off the top or the anti-top-quark. Therefore, the process of tth0 associated production at future colliders is not only particularly suitable in discovering the Higgs boson with the intermediate mass, but also helpful in measuring the Yukawa coupling strength. The charged Higgs boson in MSSM plays an important role in the extensions of the SM, its discovery in experiment will unequivocally imply the existence of the physics beyond the SM. An important production mode is the production of single charged Higgs boson, especially when the charged Higgs boson is too heavy to be produced in pair at linear colliders. Among various single charged Higgs boson production channels, e+e-→Φ0H±W? (Φ0 = h0,H0,A0), are excellent channels in studying the interactions among neutral Higgs boson(h0, H0 or A0), charged Higgs boson and gauge boson, and is a useful alternative channel for studying the phenomenology of charged Higgs boson.The main innovations in this thesis are listed below:For the first time we investigate the effect of the LH model on neutral Higgs boson pair production via both gluon and bottom fusions at the CERN Large Hadron Collider (i.e., gg→H0H0 and bb→H0H0 ) at the complete lowest order in detail, and discuss the top quark FCNC rare decay t→cH0 in the LH model. Further more, we independently deduce part of interaction Feynman rules of the Littlest Higgs model.The process of tth0 associated production at future colliders is an important instrument in measuring the Yukawa coupling strength. The precise calculation is necessary to distinguish the property of the Yukawa coupling in different models. We study the full one-loop electroweak correction of this process accurately, and use tree-level Higgs masses through out the loop calculation to keep the gauge invariance, while for the phase space integration, the matrix element needs to be expressed in terms of physical masses for the external final-states.The charged Higgs boson plays an important role in MSSM, its discovery in experiment will unequivocally imply the existence of the physics beyond the SM. We precisely investigate the full one-loop electroweak correction of the process e+e-→Φ0H±W? (Φ0 = h0,H0,A0). In the calculation, we present the details for treating the charged Higgs boson resonance in the calculation up to one-loop level, and generally adopt the MSSM parameters at the reference point SPS1a’ defined in the SPA project.

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CLC: > Mathematical sciences and chemical > Physics > Nuclear physics,high energy physics > High-energy physics > Particle physics > Symmetrical nature of conservation theorems
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