Identification of single top-quark production in the Wt channel using a kinematic fit at ATLAS

The Wt channel is predicted to give the second largest contribution to the total single top-quark production cross section in proton-proton collisions at the LHC. Furthermore it still is a discovery channel, as at the Tevatron its cross section is almost negligible. The Wt channel is characterised by the associated production of a top-quark and an on-shell W boson. In the lepton plus jets decay channel this leads to one b-quark jet, two light-quark jets, one charged lepton and a neutrino - manifesting itself in missing transverse energy - in the final state. The study presented tries to reconstruct the decay chain from the measured final state by using a kinematic fitter. The results of the fit are then used to separate the signal from the various brackgrounds, in particular the t anti t channel, which intereferes with single top Wt production at NLO and is therefore of particular importance for any Wt channel analysis.