White Rose University Consortium logo
University of Leeds logo University of Sheffield logo York University logo

Searches for supersymmetric partners of third generation quarks and measurement of the ttbar+Z process using the ATLAS detector at the CERN Large Hadron Collider

McFayden, Joshua A (2013) Searches for supersymmetric partners of third generation quarks and measurement of the ttbar+Z process using the ATLAS detector at the CERN Large Hadron Collider. PhD thesis, University of Sheffield.

This is the latest version of this item.

[img]
Preview
Text
PHD.pdf
Available under License Creative Commons Attribution-Noncommercial-No Derivative Works 2.0 UK: England & Wales.

Download (6Mb) | Preview

Abstract

This thesis presents results using data collected by the ATLAS experiment during 2011 and 2012 at √s = 7 TeV and 8 TeV respectively. The focus of the work presented in this thesis is separated into two areas, measurement of the tt ̄+Z process and searches for the supersymmetric partners to third generation quarks. Firstly, a search for tt ̄+ Z production using 4.7 fb−1 of √s = 7 TeV data is described including the generation of the dedicated simulated signal Monte Carlo samples for the analysis. The result is interpreted in terms of a 95% probability upper limit on the tt ̄+ Z production cross section of 0.71 pb. This is compatible with NLO Standard Model prediction of 0.14 pb. Secondly, a number of searches for the supersymmetric partners of bottom (sbottom) and top (stop) quarks are described. The first is a search for sbottom squark pair production in the b_1 → b_1 χ^0_1 decay channel using 2.05 fb−1 of √s = 7 TeV ATLAS data. No significant excess is observed above the Standard Model expectation and exclusion limits at the 95% confidence level are set in the m_b_1 − m_χ^0_1 plane. For a massless neutralino sbottom masses are excluded up to 390 GeV. For neutralino mass of 120 GeV sbottom masses are excluded for 275 < m_b_1 < 350 GeV. Finally two searches for stop squark pair production in the t_1 → t_! χ^0_1 decay channel are described, one using 4.7 fb−1 of √s = 7 TeV data and the other using 20.5 fb−1 of √s = 8 TeV data. Again, no significant excess is observed above the Standard Model expectation and exclusion limits at the 95% confidence level are set in the m_t1 − m_χ^0_1 plane. For a nearly massless neutralino, stop masses between 320 and 660 GeV are excluded. For neutralino mass of 150 GeV, stop masses are excluded between 400 and 620 GeV.

Item Type: Thesis (PhD)
Academic Units: The University of Sheffield > Faculty of Science (Sheffield) > Physics and Astronomy (Sheffield)
Identification Number/EthosID: uk.bl.ethos.595068
Depositing User: Mr Joshua A McFayden
Date Deposited: 11 Mar 2014 15:05
Last Modified: 03 Oct 2016 11:04
URI: http://etheses.whiterose.ac.uk/id/eprint/5264

Available Versions of this Item

You do not need to contact us to get a copy of this thesis. Please use the 'Download' link(s) above to get a copy.
You can contact us about this thesis. If you need to make a general enquiry, please see the Contact us page.

Actions (repository staff only: login required)