Tuning of parameters sensitive to colour reconnection in the Pythia 8 event generator using top-quark-antiquark pair production events recorded with the ATLAS detector

In this master thesis, Monte Carlo models describing the reorientation of QCD colour interactions (”colour reconnection”) in an event are fitted to experimental data taken at ATLAS. For this purpose, new techniques for evaluating the sensitivity and envelopment of the reference data are developed and applied. Furthermore, an adjustment of the weighting of individual observables to reduce the influence of redundant observables is investigated. The three resulting ”tunes” are presented in Table 1. These are compared in the thesis on the basis of their contribution to the2 goodness-of-fit $\chi^2$. In addition, a comparison is made to the widely used A14 tune. The masses of top quarks and $W$ bosons reconstructed using the produced tunes are compared to A14.