This thesis introduces readers to the Standard Model, the top quark and its properties, before explaining the concept of spin correlation measurement. The first measurement of top quark spin correlations at the LHC in the lepton+jets decay channel is presented.
As the heaviest elementary particle, the top quark plays an essential role in the Standard Model of elementary particle physics. In the case of top quarks being produced in pairs at hadron colliders, the Standard Model predicts their spins to be correlated. The degree of correlation depends on both the production mechanism and properties of the top quark. Any deviation from the Standard Model prediction can be an indicator for new physics phenomena. The thesis employs an advanced top quark reconstruction algorithm including dedicated identification of the up- and down-type quarks from the W boson decay.

Auteur
Boris Lemmer studied physics at the Universities of Gießen and Umeå. He worked within the CrystalBall/TAPS collaboration on the study of in-medium properties of hadrons. For his PhD thesis at the University of Göttingen he joined the ATLAS collaboration and studied the properties of the top quark, which is still his research focus.

Contenu
Standard Model, Top Quarks and Spin Correlation.- Experimental Setup.- Analysis Objects.- Dataset, Signal and Background Modelling.- Event Selection and Reconstruction.- Analysis Strategy.- Systematic Uncertainties.- Results.- Summary, Conclusion and Outlook.