A search for supersymmetry is presented based on proton-proton collision events containing identified hadronically decaying top quarks (i.e., events with no identified leptons), and an imbalance EmissT in transverse momentum. The data were collected with the Compact Muon Solenoid (CMS) detector at the CERN Large Hadron Collider (LHC) at a center-of-mass energy of 13 TeV, and correspond to an integrated luminosity of 35.9 fb-1. The 84 exclusive search regions are defined in terms of the multiplicity of bottom quark jet and top quark candidates, the missing energy, the scalar sum of jet transverse momenta HT, and the transverse mass variable sensitive to the pair production of heavy particles, each of which decays into an invisible particle MT2. A novel and robust top quark reconstruction algorithm which is based on multivariate approach and is capable of identifying top quarks in the wide spectrum of top quark transverse momentum is developed. Methods in the modeling of events arising from quantum chromodynamics and electroweak boson production, which are major backgrounds in searches for new physics at the LHC, are also presented. No statistically significant excess of events is observed relative to the expectation from the standard model. Discussion of the non-excluded regions of the model parameter space is given. Lower limits on the masses of supersymmetric particles are determined at 95% confidence level in the context of simplified models with top quark production. For a model with direct top squark pair production followed by the decay of each top squark to a top quark and a neutralino, top squark masses up to 1020 GeV and neutralino masses up to 430 GeV are excluded. For a model with pair production of gluinos followed by the decay of each gluino to a top quark-antiquark pair and a neutralino, gluino masses up to 2040 GeV and neutralino masses up to 1150 GeV are excluded. These limits extend previous results obtained with 8 TeV data and 2.3 fb-1 13 TeV data.
| Identifer | oai:union.ndltd.org:fiu.edu/oai:digitalcommons.fiu.edu:etd-4937 |
| Date | 08 June 2018 |
| Creators | Joshi, Yagya R |
| Publisher | FIU Digital Commons |
| Source Sets | Florida International University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | FIU Electronic Theses and Dissertations |
| Rights | http://creativecommons.org/licenses/by-nc-nd/4.0/ |
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