Göttingen 2012 – scientific programme

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T: Fachverband Teilchenphysik

T 34: Top-Quark: Produktion 3

T 34.4: Talk

Wednesday, February 29, 2012, 17:30–17:45, ZHG 104

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

The ATLAS experiment at CERN has recently collected almost 5 fb^-1 of good quality pp collision data at a centre of mass energy of 7 TeV. This is a great chance for new physics discoveries and precision studies of the Standard Model. In the context of the top quark physics, a specific interest is devoted to the production of single top quarks, since only electroweak couplings are involved, which makes this production very important for identifying and test in detail some slight deviations from the predictions of the Standerd 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, resulting in an ambiguity of final state W bosons, which makes the top very difficult to reconstruct univocally. For this reason a kinematic fitting procedure is used, both to identify the top quark as well as 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, along with the procedure for the rejection of the background exploiting the full potential of the same kinematic fitting tool used for extracting the signal. The last results involving the measurement of the production cross section for the Wt channel will be presented.