Top-Quark Pair Production Cross Sections and Calibration of the Top-Quark Monte-Carlo Mass: Measurements Performed with the CMS Detector Using LHC Run I Proton-Proton Collision Data
This thesis presents the first experimental calibration of the top-quark Monte-Carlo mass. It also provides the top-quark mass-independent and most precise top-quark pair production cross-section measurement to date. The most precise measurements of the top-quark mass obtain the top-quark mass parameter (Monte-Carlo mass) used in simulations, which are partially based on heuristic models. Its interpretation in terms of mass parameters used in theoretical calculations, e.g. a running or a pole mass, has been a long-standing open problem with far-reaching implications beyond particle physics, even affecting conclusions on the stability of the vacuum state of our universe.
In this thesis, this problem is solved experimentally in three steps using data obtained with the compact muon solenoid (CMS) detector. The most precise top-quark pair production cross-section measurements to date are performed. The Monte-Carlo mass is determined and a new method for extracting the top-quark mass from theoretical calculations is presented. Lastly, the top-quark production cross-sections are obtained – for the first time – without residual dependence on the top-quark mass, are interpreted using theoretical calculations to determine the top-quark running- and pole mass with unprecedented precision, and are fully consistently compared with the simultaneously obtained top-quark Monte-Carlo mass.
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3 The LHC and the CMS Experiment
4 Event Reconstruction and Selection
5 Measurement of the TopQuark Pair Production Cross Section
6 Extraction of the TopQuark Mass
7 Calibration of the TopQuark MonteCarlo Mass
8 Summary and Conclusions
Appendix AMonte Carlo Parameters
Appendix BDetermination of Trigger Efficiencies
Appendix CFitted Parameters and Correlations
Appendix DExtraction of mt from mlb
Appendix EFitted Parameters and Correlationsin the Fit of σtt and mMCt
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7TeV added in quadrature additional jets b-tagged background 2 b-jets background 7TeV background processes beam bjet boson calculations calorimeter CERN CMS Collaboration collisions correlations corresponding defined determined Diboson background distribution efficiency employed energy scale event reconstruction event yields extracted extrapol fermion gluon hadron colliders Higgs boson interaction invariant mass Jet energy resolution JHEP lepton candidate luminosity MadGraph+pythia mcfm ME-PS matching measured minimum pt Mistag mMCt mminlb mminlb,pred mMSt modeling mp,convt mpolet Name Pull Constr/o NNLO nuisance parameters Pair Production Cross particles phase space photon Phys Pileup precision predicted production cross section quantum chromodynamics quark quark mass reconstructed Relative Stat renormalization resulting scale 8 TeV scale factors shaded band simulation statistical uncertainty systematic uncertainties t¯t production cross t¯t signal Tevatron Top pt top-quark mass Top-Quark Pair Production top-quark pole mass total uncertainty trigger variations vº HLT W-boson