Modelling of top quark pairs production in association with Standard Model bosons or heavy quark pairs.

Production of top quark pairs in association with heavy Standard Model bosons or with heavy flavour quark-pairs is important both as a signal and a background in several ATLAS analyses. Strong constraints on such processes cannot at present be obtained from data, and therefore their modeling by Monte Carlo simulation as well as the associated uncertainties are important. This poster documents the Monte Carlo samples currently being used in ATLAS for the ttH and ttV (V=W,Z vector bosons) and tt+bottom and charm quark pairs processes for sqrt(s)=13 TeV proton-proton collisions.