MC modelling uncertainty studies of the t anti tH process

Among the Higgs production channels with H → b anti b, the Higgs boson production in association with top quarks is especially important since it allows the measurement of the Higgs boson to top quark couplings predicted by the Standard Model. Besides the need for high statistics, one challenging factor in background dominated t anti tH searches is the minimization of systematic uncertainties. The Monte Carlo (MC) signal and background modelling represents one of the main sources of systematic uncertainties in the analysis. To evaluate the systematic uncertainty on the t anti tH signal model, recent theoretical calculations at NLO QCD accuracy were compared to simulations performed by Pythia. Furthermore, the effect of the variation of the renormalization and factorization scales in NLO MC is studied as well as the difference in the t anti tH signal model between Pythia 6 and 8 that were used to generate t anti tH signal at √(s) = 7 and 8 TeV, respectively.