Top-Antitop spin correlation measurement in the semi-leptonic decay channel in the ATLAS experiment.

The study of spin correlation in ttbar events produced at the LHC can probe for possible new physics in the strong production vertex. Effects of a few percent in the decay products observables and a high ttbar event production rate, expected during the first years of running of the ATLAS experiment, should allow the measurement of this correlation. This note presents the sensitivity of the ATLAS experiment to measure ttbar spin correlation in the channel ttbar --> WbWb --> lepton neutrino b jet jet b and compared it with the dileptonic mode ttbar --> WbWb --> lepton neutrino b lepton neutrino b.