Quantum Chromodynamics is the underlying theory of hadrons and their interactions. In deriving results from this theory one relies on perturbative calculations. Sometimes indirect methods have been explored to circumvent direct calculation of pure gluonic amplitudes. For example, it has been shown that supersymmetric extension of QCD along with supersymmetric Ward identities can be used to establish relations between amplitudes with the same total number of particles but a different number of gluons. Such relations are used here to connect pure gluonic and pure fermionic amplitudes in the case of 4-pt and 6-pt functions. These relations offer an indirect way of calculating tree level pure gluonic amplitudes since these amplitudes are identical in supersymmetric and non-supersymmetric QCD. The aforementioned relations however, provide no insight into the relation between Feynman diagram of the amplitudes involved. In this regard, we investigate the relation between individual Feynman diagrams in the Wess-Zumino model. / Another calculational difficulty arises when one is concerned with high energy scattering in QCD. In the high energy regime, because the effective coupling constant is relatively large, it is necessary to sum up an infinite number of diagrams. This is made even more difficult due to the cancellations in certain color channels that occurs at any perturbative order. The new non-abelian cut diagram technique provides considerable assistance by giving the result with the cancellations already built into its rules. Sixth-order calculations are carried out to show the efficiency of this technique. Finally, we consider the question of diagram with fermion loops that need regularization because of their UV divergence. We find that regularization leads to an enhancement in their high energy behavior.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.34641 |
| Date | January 1997 |
| Creators | Hamidi-Ravari, Omid. |
| Contributors | Lam, C. S. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Physics.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001618321, proquestno: NQ36979, Theses scanned by UMI/ProQuest. |
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