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T: Fachverband Teilchenphysik

T 38: Top-Produktion III

T 38.8: Talk

Wednesday, March 30, 2011, 18:30–18:45, 30.22: 130

Single-top in Wt Associated Production at ATLAS — •Michelangelo Giorgi — Humboldt Universität zu Berlin, Berlin, Deutschland

The ATLAS experiment at CERN has recently collected over 40 pb^-1 of pp collision data at a centre of mass energy of 7 TeV, opening a new window for discoveries and precision studies of the Standard Model. In this view, within the context of top quark physics a specific interest is devoted to the production of single top quarks, since only electro-weak couplings are involved, which make this production a very important framework to identify and test in detail some deviations from the predictions of the Standard Model which might appear. The Wt-channel is the second most important contribution to the total single-top production at the LHC. It is characterized by the production of a single top quark plus an associated real W boson in the final state. The subsequent weak decay of the t-quark is cause of an ambiguity between both W bosons in the final state which makes the top very difficult to reconstruct univocally. For this reason a kinematic fitting procedure is used, both to identify the top quark and the associated W boson in the event. The channel is analyzed in the semi-leptonic decay mode of the two W bosons, leading to a final state composition of one b-jet, two light jets, one lepton and missing transverse energy. The kinematics of the Wt production mode will be shown as well as the background rejection and the application of a tt veto based on the same kinematic fitting tool used for extracting the signal. Some first results obtained from data will be presented.