Study of the Powheg-bb4l generator including non-resonant and off-shell effects in comparison with other MC generator predictions

The precise simulation of $t\bar{t}$ processes is crucial for precision tests of the Standard Model and in the search for new physics at the Large Hadron Collider (LHC). The bb4l generator is a next-to-leading order (NLO) matrix-element generator for $pp \rightarrow l^+\nu_{l}l^{-}\bar{\nu}_{l}b\bar{b}$ final states implemented in Powheg. It includes theoretical improvements in the simulation of $t\bar{t}$ processes, which allows the production of $t\bar{t}$ and $tW$ events including interference and off-shell effects. The events simulated with the bb4l generator are interfaced with Pythia 8 for the simulation of the Parton Shower (PS) and hadronisation. They are compared to $t\bar{t} + tW$ samples produced with various NLO+PS setups, where different diagram-removal and diagram-subtraction methods are used in the generation of the $tW$ events. The studies include comparisons between different Monte Carlo generator setups. In particular, the studies are performed in an inclusive phase-space relevant for measurements such as the top-quark mass and in phase-spaces relevant for searches.