Studies of $t\bar{t}/tW$ interference effects in $b\bar{b}\ell^{+}\ell^{-'}\nu\bar{\nu}'$ final states with Powheg and MG5_aMC@NLO setups

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. Up to now, the interference effects between $t\bar{t}$ and $tW$ production were taken into account by using either a diagram-removal (DR) or a diagram-subtraction (DS) method in the generation of the $tW$ events. The ``$bb4\ell$'' generator is a NLO matrix-element generator for $pp \to b\bar{b}\ell^{+}\ell^{-'}\nu\bar{\nu}'$ final states implemented in the Powheg-Box. 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, off-shell effects, and top-quark decays at NLO. The events simulated with the $bb4\ell$ generator are interfaced with Pythia 8 for the simulation of the Parton Shower (PS) and hadronisation and compared to different $tW$ generator setups. In addition, different DR and DS models implemented in MG5_aMC@NLO are studied. Their NLO predictions are compared to unfolded ATLAS data and to the $bb4\ell$ predictions. The studies are performed in a phase-space for typical $t\bar{t}$ precision measurements as well as in phase-spaces relevant for searches.