A Search for Evidence of New Particle Production in Semi-leptonic Top Quark Pair Events with at least one Photon and MET of pp Collisions at sqrt(s) of 13 TeV

Author: ORCID icon orcid.org/0000-0001-9039-1380
Xia, Fan, Physics - Graduate School of Arts and Sciences, University of Virginia
Cox, Bradley, AS-Physics, University of Virginia

This dissertation presents a search for evidence of new particle production motivated by the theory of Supersymmetry beyond the Standard Model, in particular the scenario of gauge mediated supersymmetry breaking models. The strong production of top squark pairs yields events with top quark pairs and pairs of neutralinos where each neutralino decays to photon and undetected gravitino which leads to the significant missing transverse momentum. Semi-leptonic top quark pair events with exactly one lepton (electron or muon), b-jet, and at least one energetic photon are selected. The spectra of missing transverse momenta of observation against the expected spectra of Standard Model processes are compared to search for the imbalance which would result from Supersymmetry. The search is performed on the full 2016 dataset of proton-proton collisions at the center-of-mass energy 13 TeV collected by the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC), corresponding to an integrated luminosity of 35.87 /fb. No evidence of Supersymmetry is found in this analysis. The result of this search is interpreted to set an upper limit which excludes top squark masses up to 1000 GeV/cc, exceeding previous results by 250 GeV/cc.

PHD (Doctor of Philosophy)
Particle physics, Supersymmetry, High energy experiment, CMS
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