Higher Order QCD Radiation in Top Pair Production with the CMS Detector

The Large Hadron Collider at CERN will collide protons with a centre-of-mass energy of up to √s = 14TeV, thereby offering the opportunity to explore a wide range of physics topics. In this thesis the effects of QCD radiation in top pair events are examined. Due to the large top mass, top pairs are well suited for an investigation of gluon emissions. An extensive study comparing different radiation models implemented in Monte Carlo event generators is presented. The transverse momentum distribution of the $t\bar{t}$ system is rather sensitive to radiation influences and therefore analysed in detail. As hard emissions can be associated with jets, a thorough investigation of these jets is performed. The transverse momentum of hard jets and the rapidity distribution of the hardest jet in the $t\bar{t}$ rest frame are examined. Moreover an analysis of samples incorporating different radiation models after the full CMS detector simulation is presented, studying the same observables as on generator level. The potential of the CMS experiment to distinguish between different models is estimated and a method to obtain the underlying transverse momentum distribution of the $t\bar{t}$ system is described.