Description
- Abstract:
- The top quark is the heaviest of the six observed quarks in the Standard Model (SM). Its mass is more than an order of magnitude greater than any other SM fermion, and hence a precise measurement of this mass provides constraints on the Higgs boson and many other hypothetical particles. In this analysis, we measure the mass of the top quark using the 36 pb-1 of data collected by the CMS experiment from the collisions of the LHC at √s = 7 TeV center-of-mass energy during the year 2010.<br/> <br/> At the LHC, top-antitop quark pairs are expected to be produced predominantly through gluon fusion and decay almost exclusively to two W bosons and a bottom-antibottom quark pair. We consider a W boson decay leptonic if it results in a muon or an electron and label the decay channel based on the number of leptonic W decays. Here, we report on the measurement of the mass of the top quark in the dilepton channel.<br/> <br/> The dilepton final state consists of two jets originating from the bottom quarks, two charged leptons and two neutrinos. The latter are not visible to our detector, which results in six unknown parameters. Five of these can be solved for using constraints arising from transverse momentum conservation, the mass of the W boson and the equality of masses of the top and antitop quarks. To deal with the under-constrained system, we use the Analytical Matrix Weighting Technique. This method iterates over many values of the top quark mass and analytically solves the system using the top quark mass as the missing constraint. Each value of the mass is given a weight based on the kinematics of top quark production and decay. The mass estimator for each event is the value with the highest weight and the mass of the top quark is extracted from these estimators by performing a maximum likelihood fit to simulated templates constructed for various masses. The measured value of the top quark mass from this analysis is mt = 175.8 ± 4.9 (stat) ± 4.5 (syst) GeV/c2.
- Notes:
- Thesis (Ph.D. -- Brown University (2012)
Access Conditions
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Citation
Avetisyan, Aram,
"Measurement of the Top Quark Mass in the Dilepton Channel at the CMS Experiment"
(2012).
Physics Theses and Dissertations.
Brown Digital Repository. Brown University Library.
https://doi.org/10.7301/Z07D2SFG
