Muon Reconstruction Performance Of The Atlas Detector In Proton Proton Collision Data At S

Muon Reconstruction Performance of the ATLAS Detector in Proton-proton Collision Data at S√

Muon Reconstruction Performance of the ATLAS Detector in Proton{u2013}proton Collision Data at {u221A}s

This article documents the performance of the ATLAS muon identification and reconstruction using the LHC dataset recorded at √s=13 TeV in 2015. Using a large sample of J/? → ?? and Z → ?? decays from 3.2 fb-1 of pp collision data, measurements of the reconstruction efficiency, as well as of the momentum scale and resolution, are presented and compared to Monte Carlo simulations. Furthermore, the reconstruction efficiency is measured to be close to 99% over most of the covered phase space (

Spin Correlations in tt Events from pp Collisions

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.