Studies of simultaneous measurements of top quark pair production associated with an off-shell $Z$-/$W$-Boson in the trileptonic channel with ATLAS

This Bachelor’s thesis studies the simultaneous measurements of top quark pair events with a $Z$/$W$-boson in off-shell regions. These processes are difficult to distinguish because their measured signals are similar. The trileptonic channel is exclusively analysed since it provides a cleaner event signature in comparison to hadronic or single leptonic channels. For the classification, two separate approaches are used. One is based on cuts to several variables which are derived from event distributions. For the other approach, a neural network is implemented and trained to define abstract class scores which are used for classification. Additionally, EFT sensitivity is analysed in these off-shell regions because SM-EFT contributions are expected to increase for higher energy scales.