The perturbative regime of Quantum Chromodynamics (QCD) is considered and certain aspects related with higher order corrections (HOC) are studied. Certain large correction terms in the perturbative expansion are determined, in particular for large transverse momentum $(p sb{T})$ direct photon production. The origin of these terms is specified and simple forms, called K-factors, are provided (soft gluon approach). / Furthermore, for processes initiated by 2 $ to$ 2 particle subprocesses the structure of the complete HOC is analyzed. It is shown that when structure functions and/or fragmentation functions are involved, there is a gauge invariant part that dominates HOC over a sizable kinematic range. Simple and general expressions are derived allowing an easy calculation of this part. Also, it is shown that, under certain approximations, this part reduces to the form of the simple K-factors. / Other aspects of HOC, in particular the dependence on the choice of scales, are considered. Using complete HOC, detailed analysis of recent and old data on large-$p sb{T}$ direct photon production is carried out. The dependence of the form of the gluon distribution on the choice of the scales (physical versus optimal scales) is discussed and it is concluded that appreciable ambiguity in this distribution still remains.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.74317 |
| Date | January 1989 |
| Creators | Papadopoulos, Stavros |
| 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: 001072544, proquestno: AAINN63607, Theses scanned by UMI/ProQuest. |
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