Effective field theory for top quark physics

Zhang, Cen

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https://hdl.handle.net/2142/29627 Copy

Description

Title

Effective field theory for top quark physics

Author(s)

Zhang, Cen

Issue Date

2012-02-06T20:07:38Z

Director of Research (if dissertation) or Advisor (if thesis)

Willenbrock, Scott S.

Committee Member(s)

• Willenbrock, Scott S.
• Stack, John D.
• Stelzer, Timothy J.

Department of Study

Physics

Discipline

Physics

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• top quark
• effective field thoery
• precision electroweak data

Abstract

The top quark plays an important role in the search for physics beyond the standard model because of its large mass. In the situation where new physics exist at an energy scale higher than the scale we can probe directly, it is desirable to have a model-independent approach, which we can use to parametrize and to constrain possible new physics. In this dissertation an effective-field-theory approach to top quark physics is suggested. In this approach, the leading effects of new physics at relatively low energy scale is parametrized by effective operators which have mass dimension six. We first consider top-quark decay, single top production, and top-quark pair production in hadron colliders. We classify all dimension-six operators and identify 15 operators that contribute to these processes. We compute the deviation from the standard model induced by these operators. The results provide a systematic way of searching for (or obtaining bounds on) physics beyond the standard model. We then turn to precision electroweak experiments. We study the effect of one dimension-six operator involving the top quark and the electroweak gauge bosons on precision electroweak data via a top-quark loop. We demonstrate the renormalizability, in the modern sense, of the effective field theory. We use the oblique parameter U to bound the coefficient of this operator, and compare with the bound derived from measurements on top-quark decay. Finally, we extend this analysis to include 8 dimension-six operators which generate anomalous interactions among the electroweak gauge bosons and the top quark. We calculate their corrections to all major precision electroweak observables. The corrections are compared with data to obtain constraints on these operators.

Graduation Semester

2011-12

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http://hdl.handle.net/2142/29627

Copyright and License Information

Copyright 2011 Cen Zhang

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