A search for top-antitop quark resonances with the ATLAS detector at the LHC

Duncan, Anna (2019) A search for top-antitop quark resonances with the ATLAS detector at the LHC. PhD thesis, University of Glasgow.

Abstract

Various extensions to the Standard Model postulate the existence of heavy particles that decay to a top-antitop quark pair. If one of these particles exists with a mass of a few TeV then it may be produced during proton-proton collisions at the Large Hadron Collider (LHC). The analysis presented in this thesis searches 36 fb−1 of √s = 13 TeV proton- proton collision data collected by the ATLAS detector for evidence of a top-antitop quark resonance, and sets upper limits on the production cross section of new heavy particles in a set of benchmark models. The observed top-antitop quark invariant mass spectrum agrees well with the spectrum expected under the Standard Model and no evidence of a top-antitop quark resonance is found. A 1% width Z′ boson in a topcolour-assisted technicolour model is observed to be excluded at masses below 3.0 TeV, a 30% (15%) width Kaluza-Klein gluon in a Randall-Sundrum model is observed to be excluded at masses below 3.7 TeV (3.8 TeV), and a 3-6% width Kaluza-Klein graviton in a Randall-Sundrum model is observed to be excluded in the mass interval 0.45 < mGKK < 0.65 TeV. Some techniques developed to improve the sensitivity of the analysis are described: a new method of electron-in-jet overlap removal and a reconstruction of semi-boosted and very boosted top-antitop quark decay topologies. A study evaluating the prospects of this search at the High Luminostiy LHC is also presented. It estimates that a search of 3000 fb−1 of proton-proton collision data collected using an upgraded ATLAS detector will be able to exclude a Z′ boson at masses below 4 TeV.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Supported by funding from Science and Technology Facilities Council (STFC).
• Keywords: LHC ATLAS.
• Subjects: Q Science > QC Physics
• Colleges/Schools: College of Science and Engineering > School of Physics and Astronomy
• Supervisor's Name: Buttar, Professor Craig
• Date of Award: 2019
• Depositing User: Anna Duncan
• Unique ID: glathesis:2019-73014
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 11 Jun 2019 10:13
• Last Modified: 05 Mar 2020 22:22
• Thesis DOI: 10.5525/gla.thesis.73014
• URI: https://theses.gla.ac.uk/id/eprint/73014

Related URLs

• Article DOI
• Enlighten Publications Record
• Article DOI
• Enlighten Publications Record