Effective field theory for top quark physics

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.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2012

Author dc:creator

• Zhang, Cen

Contributors dc:contributor

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

• top quark
• effective field thoery
• precision electroweak data

Statement dc:rights

• Copyright 2011 Cen Zhang

Language dc:language

en

Handle dc:identifier

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

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/29627