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Search for Pair-Produced Supersymmetric Top Quark Partners with the ATLAS Experiment
Stockholm University, Faculty of Science, Department of Physics. (ATLAS)ORCID iD: 0000-0003-0403-3697
2016 (English)Doctoral thesis, monograph (Other academic)
Abstract [en]

Searches for the supersymmetric partner of the top quark (stop) are motivated by natural supersymmetry, where the stop has to be light to cancel the large radiative corrections to the Higgs boson mass. This thesis presents three different searches for the stop at √s = 8 TeV and √s = 13 TeV using data from the ATLAS experiment at CERN’s Large Hadron Collider. The thesis also includes a study of the primary vertex reconstruction performance in data and simulation at √s = 7 TeV using tt and Z events. All stop searches presented are carried out in final states with a single lepton, four or more jets and large missing transverse energy. A search for direct stop pair production is conducted with 20.3 fb−1 of data at a center-of-mass energy of √s = 8 TeV. Several stop decay scenarios are considered, including those to a top quark and the lightest neutralino and to a bottom quark and the lightest chargino. The sensitivity of the analysis is also studied in the context of various phenomenological MSSM models in which more complex decay scenarios can be present. Two different analyses are carried out at √s = 13 TeV. The first one is a search for both gluino-mediated and direct stop pair production with 3.2 fb−1 of data while the second one is a search for direct stop pair production with 13.2 fb−1 of data in the decay scenario to a bottom quark and the lightest chargino. The results of the analyses show no significant excess over the Standard Model predictions in the observed data. Consequently, exclusion limits are set at 95% CL on the masses of the stop and the lightest neutralino.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University , 2016. , 162 p.
Keyword [en]
ATLAS, supersymmetry, SUSY, Beyond Standard Model, stop, pMSSM, Large Hadron Collider, LHC, CERN
National Category
Subatomic Physics
Research subject
Physics
Identifiers
URN: urn:nbn:se:su:diva-132289ISBN: 978-91-7649-475-2OAI: oai:DiVA.org:su-132289DiVA: diva2:951062
Public defence
2016-09-26, sal FB42, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:00 (English)
Opponent
Supervisors
Available from: 2016-09-01 Created: 2016-08-05 Last updated: 2016-08-24Bibliographically approved

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Abulaiti, Yiming
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Department of Physics
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