Untersuchungen zur Kombinatorik von Jets in Ereignissen mit Top-Paaren sowie zusätzlicher Jets im Atlas-Experiment am LHC

The detailed measurement of top-quarks allows one to draw conclusions about theories beyond the standard model. Due to its high mass, the top-quark is important for electroweak symmetry breaking, which generates mass terms for fermions and gauge bosons. Top-quarks at the LHC are mainly produced via t¯t-pairs. The combinatorics of all decay channels is challenging because of multiple similar particles in the final state. Therefore algorithms for the correct reconstruction were developed. In this thesis the methods to identify the correct combination in a semileptonic sample are compared in the efficiency-purity-plane. The evaluation shows, that the use of mass information allows higher efficiency and purity than pure geometric variables. For a better use in comparison with first data, the features of additional jets are calculated with the use of these methods. Furthermore the ongoing change from AtlasCone to AntiKt jet algorithms is investigated, showing an equivalent behavior for both algorithms.