Global QCD Analysis and Electroweak Symmetry Breaking in High Energy Collider Phenomenology

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Current understanding of high energy physics is embodied in the Standard Model (SM). According to that theory, protons and neutrons, along with all other strongly interacting particles, are composed of even more fundamental particles called partons (quarks and gluons). Interactions between the partons are described by the theory of Quantum Chromodynamics (QCD). The proposed research involves continued refinement in understanding the interplay between QCD theory and experiment, which is necessary to deepen the understanding of QCD and to determine the probability distributions of the partons in the proton by global analysis. The resulting CTEQ Parton Distributions are essential to the interpretation of experiments at the world's leading high energy collider facilities: Fermilab (Batavia, IL), DESY (Hamburg, Germany), RHIC (Brookhaven, NY), and CERN (Geneva, Switzerland). The Electroweak sector of the SM is extremely successful in explaining and predicting experimental data spanning a range in energy from the atomic scale to the Z boson mass.However, one major aspect of the model remains to be elucidated: the mechanism of Electroweak Symmetry Breaking (EWSB), which generates masses for the W and Z bosons while leaving electromagnetic gauge symmetry intact. In the SM, EWSB is economically implemented through a single scalar particle called the Higgs boson. However, the SM cannot explain observations such as the hierarchical pattern of fermion masses, or the existence of dark matter; so it is widely believed that new measurements at very high energies, or very high precision, will soon turn up deviations from the SM that will point to new physics.A second part of the project represents continuation of research to probe the EWSB mechanism in high energy collisions. Special consideration is given to measuring the couplings of the top quark to W and Z gauge bosons and to (elementary or composite) Higgs boson(s); and to searching for the Higgs boson and determining its properties. These are prime objectives of experiments at the Fermilab Tevatron collider and the CERN Large Hadron Collider (LHC).The broader impacts of this project are as follows: The achievement of the project will contribute to understanding of the fundamental interactions in Nature. The project trains graduate students and postdoctoral fellows in theoretical high energy physics at MSU and at the CTEQ summer schools. It also provides opportunities for undergraduate students to participate in research through the REU program, and for high school teachers and middle school students to experience forefront research through Summer programs sponsored by MSU and the State of Michigan.