Study of $t\bar{t}b\bar{b}$ and $t\bar{t}W$ background modelling for $t\bar{t}H$ analyses

This note presents Monte Carlo generator comparisons of the $t\bar{t}b\bar{b}$ and $t\bar{t}W$ processes at particle level. The aim is to compare the modelling of important backgrounds to $t\bar{t}H$ measurements in multi-lepton final states and in the $t\bar{t}H (H \to b\bar{b})$ decay channel and the treatment of the associated theory uncertainties for a combination of the full Run-2 $t\bar{t}H$ results from ATLAS and CMS. As a first step, modelling and theory uncertainties as used in ATLAS and CMS are compared in the relevant analysis regions.