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Complete Measurement of the Top-quark Polarization in T-channel Single Top-quark Production Using Pp Collisions at 13 TeV with the ATLAS Detector

Bi, Runyu (2020) Complete Measurement of the Top-quark Polarization in T-channel Single Top-quark Production Using Pp Collisions at 13 TeV with the ATLAS Detector. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Abstract

The top quarks are undoubtedly one of the most promising and experimentally relevant probes into finding new physics. They can be produced in charged-current electroweak processes via a W tb vertex. Its unique mass scale led to a late discovery in experiment — until 1995 at the Tevatron proton-antiproton collider at Fermilab on the events from top pair production. The observation of the electroweak single top process was established even later — in 2009, also at Fermilab based on 2.3 fb-1 and 3.2 fb-1 of CDF/DØ data. Nowadays, the high energy proton-proton collider — the Large Hardon Collider (LHC), with a data set of 139 fb-1 from the ATLAS detector, makes it possible to perform precision measurements on top quarks using both tt ̄and single top channels.
At the LHC, electroweak production of single top quarks in the t-channel leads, in the standard model, to a high degree of top quark polarization. Two subprocesses, ub ! dt and db ! u ̄t contribute to t-channel production of single top, while the charge-conjugate processes contribute to production of antitop. The top (antitop) quark spin is expected to be polarized along(opposite to) the direction of the light-quark momentum. In this thesis I present a measurement of the top quark polarization produced within a fiducial region of acceptance, using an integrated luminosity 139 fb-1 of proton-proton collisions at 13 TeV, collected by the ATLAS detector. The top decay chain: t->W+b-> l+mu+b, include a lepton, a neutrino and a b quark in the final state, which interact with the ATLAS detector, allowing the top quark to be fully reconstructed. From the angular distribution of the top quark decay products, we obtain all three components of the polarization of both top quarks and top anti-quarks.


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Details

Item Type: University of Pittsburgh ETD
Status: Unpublished
Creators/Authors:
CreatorsEmailPitt UsernameORCID
Bi, Runyurunyu.bi@pitt.edurub170000-0002-5115-2288
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairBoudreau, Josephboudreau@pitt.eduboudreau
Committee MemberMuelluer, Jamesmueller@pitt.edumueller
Committee MemberHan, Taothan@pitt.eduthan
Committee MemberZentner, Andrewzentner@pitt.eduzentner
Committee MemberPaulini, Manfredpaulini@cmu.edun.a
Date: 16 September 2020
Date Type: Publication
Defense Date: 15 May 2020
Approval Date: 16 September 2020
Submission Date: 6 July 2020
Access Restriction: 1 year -- Restrict access to University of Pittsburgh for a period of 1 year.
Number of Pages: 168
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Physics
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: High Energy Physics Experiments, Top quark Physics
Date Deposited: 16 Sep 2020 13:30
Last Modified: 16 Sep 2020 13:30
URI: http://d-scholarship.pitt.edu/id/eprint/39606

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  • Complete Measurement of the Top-quark Polarization in T-channel Single Top-quark Production Using Pp Collisions at 13 TeV with the ATLAS Detector. (deposited 16 Sep 2020 13:30) [Currently Displayed]

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