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Humboldt-Universität zu Berlin - Mathematisch-Naturwissen­schaft­liche Fakultät - Experimentelle Elementarteilchenphysik

Humboldt-Universität zu Berlin | Mathematisch-Naturwissen­schaft­liche Fakultät | Institut für Physik | Experimentelle Elementarteilchenphysik | ATLAS | Theses | Combined Measurement of Single Top-Quark Production in the s and t-Channel with the ATLAS Detector and Effective Field Theory Interpretation

Sören Stamm (2018)

Combined Measurement of Single Top-Quark Production in the s and t-Channel with the ATLAS Detector and Effective Field Theory Interpretation

PhD Thesis, Humboldt-Universität zu Berlin.

This thesis presents a combined measurement of single top-quark production in the s and t-channel with the ATLAS detector at the Large Hadron Collider. The 2012 data set of proton--proton collisions at a centre-of-mass energy of 8 TeV corresponding to an integrated luminosity of 20.3 fb^{-1} is used. The event selection for both channels requires one isolated electron or muon and two jets in the final state. In order to separate signal from background events, a discriminant variable is built from likelihoods obtained with the matrix element method. The cross section for both channels are determined by a combined maximum likelihood fit, which yields sigma_{s} = 4.9 +- 1.7 pb and sigma_{t} = 82.32^{+7.0}_{-5.5} pb for the s-channel and t-channel, respectively. The correlation of the two cross section measurements is 8%. These results together with an independent measurement of the associated Wt production are used to set limits on two parameters, cbar_{phiq} and cbar_{qq}, within the framework of an effective field theory. Acceptance corrections are derived as a function of the model parameters by using fast and simplified detector simulations. These corrections are included in the statistical model and the smallest intervals that correspond to 95.5% probability are -0.132 < cbar_{phiq} < 0.048 and -0.0283 < cbar_{qq} < 0.0062 for the two parameters.