A Study of the ttbar+jets Background at LHC

A study of \ttb production at Next-to-Leading Order at $\sqrt{s}=14~$TeV using the MC@NLO model is presented. A comparison between MC@NLO and standard Monte Carlo programs with Leading Order treatment of the hard process is performed. The MC@NLO model predicts a dramatic increase of the hard radiation/jets which are not part of the decay of the \ttb system, when compared to PYTHIA. MC@NLO also provides a reasonable description of the subleading radiation. As an application, the MC@NLO \ttb production prediction is used to provide a control background sample for the Vector Boson Fusion $H \ra WW \ra ll\nu\nu$ channel. The sample obtained can be tested against data in the early stages of ATLAS data taking.