Due to the large ttΛ production cross-section at the LHC energies, the
ATLAS experiment is expected to have enough statistics to measure ttΛ
cross-section even at initial luminosities. Recent studies performed in ATLAS
on the development of ttΛ cross-section measurements in the lepton+jets
channel at sβ=10 TeV using the likelihood method will be discussed. The
expected statistical and systematic uncertainties for the cross-section
measurement using the likelihood method are evaluated for an integrated
luminosity of 50 pbβ1 of Monte Carlo (MC) simulated data. Measurements
with data that will be collected in the first year of the LHC operation are
emphasized.Comment: To be published in the proceedings of DPF-2009, Detroit, MI, July
2009, eConf C09072