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| Report/Dissertation / PhD Thesis | PUBDB-2015-03093 |
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2015
Verlag Deutsches Elektronen-Synchrotron
Hamburg
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Please use a persistent id in citations: doi:10.3204/DESY-THESIS-2015-034
Report No.: DESY-THESIS-2015-034
Abstract: The mass of the top quark is measured using a sample of ttbar candidate events with one electron or muon and at least four jets in the final state, collected by CMS in proton-proton collisions at sqrt{s}=8 TeV at the LHC. The candidate events are selected from data corresponding to an integrated luminosity of 19.7 fb^-1. For each event the top-quark mass is reconstructed from a kinematic fit of the decay products to a ttbar hypothesis. In order to minimize the uncertainties from jet energy corrections, the top-quark mass is determined simultaneously with a jet energy scale factor (JSF), constrained by the known mass of the W boson decaying to quark-antiquark pairs. A joint likelihood fit taking into account multiple interpretations per event -- the ideogram method -- is used. From the simultaneous fit, a top-quark mass of 172.15 +/- 0.19 (stat.+JSF) +/- 0.61 (syst.) GeV is obtained. Using an additional constraint from the determination of the jet energy scale in photon/Z+jet events yields m_t = 172.38 +/- 0.16 (stat.+JSF) +/- 0.49 (syst.) GeV. The results are discussed in the context of different event generator implementations. Possible kinematic biases are studied by performing the measurement in different regions of the phase space.
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