UBC Theses and Dissertations
Measurement of the ttZ production cross section in the three lepton final state with 13.0 fb−¹ of √s = 8 TeV pp collision data collected by the ATLAS detector Khazraie Zamanpour, Arash
A measurement of the ttZ production cross section with the ATLAS detector in pp collisions at the LHC is presented. The search is performed on 13.0 fb−¹ of data collected in 2012. Only final states with three leptons are considered, in which the Z boson decays to a pair of leptons and one of the W bosons coming from t → bW decays gives rise to a lepton after decay. An excess of 8.95 ± 0.62 (stat) +0.37 -0.59(sys) events above background is observed with a significance of 3.64 standard deviations above zero. We have assumed no statistical error on the acceptance or efficiency of detection. In the trilepton channel, a direct measurement of the ttZ production cross section of σ = 254 ± 104 (stat) ± 19 (sys) fb is obtained.
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