Studies of tt+cc production with MadGraph5_aMC@NLO and Herwig++ for the ATLAS experiment

Studies of the simulation of ttcc at the LHC, at a centre-of-mass energy of 13 TeV, based on next-to-leading order calculations with MadGraph5_aMC@NLO matched to Herwig++ are presented. Samples with ttcc in the three flavour scheme, in a next-to-leading order matrix element are compared to an inclusive tt sample with the charm contribution coming from the parton shower. The effects of generator-level cuts, the functional form of the renormalization and factorization scales, and the starting scale of the parton shower are investigated.