Data-Driven Determination of $t\overline{t}$ Background to Supersymmetry Searches in ATLAS

The Standard Model process of ttbar production is one of the most important backgrounds to searches for Supersymmetry (SUSY) at the Large Hadron Collider (LHC) at CERN. We describe a new method to estimate the contribution of tt->bblnqq events in SUSY searches with large missing transverse energy, multi-jets and veto against leptons with the first 200 pb^{-1} data of the ATLAS experiment. The performances of this method are evaluated with 10 TeV simulated data.