The interaction of bottom squark-mediated top quark pair production, occuring in the R-parity violating minimal supersymmetric standard model (MSSM), is proposed as an explanation of the anomalously large forward-backward asymmetry (FBA) observed at the Tevatron. It is found that this model can give a good fit to top quark data, both the inclusive and invariant mass-dependent asymmetries, while remaining consistent with the total and differential production cross-sections. The model faces very strict constraints from atomic parity violation (APV), resulting from contributions to the effective down quark-Z vertex, but this constraint may be weakened by the additional diagram which is included when top squark mixing is accounted for, and can be satisfied for suitable values of the top squark mass and mixing angle. The model is also challenged by large contributions to flavour-changing neutral currents, however these may be avoided in scenarios admitting heavy first and second generation squarks. / Ce travail propose comme explication à l'asymétrie avant-arrière, anormalement large, observée au Tevatron, le processus de production de quark top par échange de squark bottom qui s'inscrit dans le Modèle Standard Supersymétrique Minimal, avec violation de R-parité. Les resultats démontrent une bonne concordance entre les données d'asymétrie du quark top, tout en restant en accord avec la section efficace totale de production et la section efficace differentielle. Le modèle développé est fortenant contraint par les données de violation de la parité atomique, resultant des contributions au couplage effectif entre le quark down et le boson Z, mais il est possible de limiter cet effet, en prenant en considération le mélange du squark top. Ce modèle est aussi contraint par les contributions importantes aux courants neutres de changement de saveur. Cependant, si les squarks de troisième génération sont légers, ces contributions peuvent être évitées.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.114564 |
| Date | January 2013 |
| Creators | Dupuis, Grace |
| Contributors | James M Cline (Internal/Supervisor) |
| 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 | Master of Science (Department of Physics) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | Electronically-submitted theses. |
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