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A search for the pair production of scalar top quarks in hadronic final states with the CMS detector

McColl, Nickolas W.
Degree Grantor:
University of California, Santa Barbara. Physics
Degree Supervisor:
Joseph Incandela
Place of Publication:
[Santa Barbara, Calif.]
University of California, Santa Barbara
Creation Date:
Issued Date:
High energy physics
Scalar top
Dissertations, Academic and Online resources
Ph.D.--University of California, Santa Barbara, 2015

The known elementary particles and their interactions are described with incredible accuracy by the Standard Model of particle physics. Despite its success, strong experimental and theoretical concerns point to the likely existence of physics beyond the standard model, including the lack of an explanation for the vast quantity of Dark Matter and Dark Energy within this framework and the incredible level of fine-tuning required for the theory to be compatible with the measured Higgs boson mass. Supersymmetry is a broader theory that addresses many of these problems. In this dissertation I describe a search for the direct pair production of the supersymmetric partner of the top quark in hadronic final states with missing transverse momentum. This search is performed on a dataset of proton-proton collisions corresponding to an integrated luminosity of 18.9 fb-1 collected at sqrt(s) = 8 TeV with the Compact Muon Solenoid experiment at the Large Hadron Collider.

The pair production of top quarks with a single lepton in the final state, the production of a Z boson decaying to two neutrinos, and the associated production of a top quark pair with no leptons in the final state and a Z boson decaying to neutrinos form significant Standard Model backgrounds to this search. The background is suppressed with a number of techniques that include high efficiency lepton identification, a dedicated top quark pair reconstruction algorithm, and search regions defined with multivariate techniques. The background yields in the search regions are estimated with an extensive study of the processes in data control regions. The data are compatible with the predicted backgrounds and the results are interpreted as exclusion limits in terms of the Simplified Model Spectra framework.

The sensitivity of this search to models with a top squark decaying to jets and a neutralino through a on-shell top quark extends to 775 GeV in top squark mass and to 650 GeV in models with a top squark decaying through an intermediate chargino.

Physical Description:
1 online resource (242 pages)
UCSB electronic theses and dissertations
Catalog System Number:
Inc.icon only.dark In Copyright
Copyright Holder:
Nickolas McColl
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