Two-loop corrections and top threshold effects in calculation of observables at the Z peak
Increasingly precise high-energy experiments now make possible tests at the quantum level of the Standard Model. This requires computation of the experimental observables in the field theory beyond tree level. Through these higher-order calculations one can relate experimental measurements to unknown parameters of the theory, such as the masses of the top quark and Higgs boson. The authors put limits on allowable values for the top quark mass, and once that mass is known the results will provide either a consistency check of the gauge field theory or evidence for new physics beyond the Standard Model. In this thesis electroweak observables and the Z peak, recently measured with high precision, are evaluated, consistently including all of the dominant two-loop corrections. Corrections are expressed using the parameters {Delta}r, {rho}, and sin {sup 2}{bar {theta}}{sub W}, which are formulated in terms of the dressed gauge boson propagators and are properly resummed. Top quark threshold effects are also studied in this framework. These are essentially non-perturbative; that is, they do not appear as a result of loop calculations. The effect of the threshold is calculated using dispersion relation techniques. They discuss the variation of the values of m{sub t} extracted from the LEP observables caused by inclusion of the two-loop corrections and of the threshold, comparing them to the uncertainty created by the lack of knowledge, of M{sub H}. The two-loop corrections are sizeable, and should be included in any attempt to extract the unknown top and Higgs masses from high-energy data. The threshold likewise changes the extracted value of m{sub t} significantly.
- Research Organization:
- Univ. of Wisconsin, Madison, WI (United States)
- OSTI ID:
- 39357
- Resource Relation:
- Other Information: TH: Thesis (Ph.D.); PBD: 1993
- Country of Publication:
- United States
- Language:
- English
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