Mainz 2014 – scientific programme

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T: Fachverband Teilchenphysik

T 61: Top-Quarks: Single Top

T 61.6: Talk

Tuesday, March 25, 2014, 18:00–18:15, P102

Optimization of the Wt associated production analysis at ATLAS using kinematic fitting and neural networks — Ian C. Brock, •Irina Cioara, Sebastian Mergelmeyer, Pienpen Seema, Jan A. Stillings, and Thomas Velz — Physikalisches Institut, University of Bonn

The second largest contribution to single top-quark production at the LHC comes from the associated production of a top quark and a real W boson (Wt channel). The lepton + jets decay topology of this channel produces one b-quark jet, one charged lepton, two light-quark jets and one neutrino.

The main sources of background for the Wt signal are top-quark pair production and events with a W boson and extra jets. An artificial neural network is used to separate signal from background. The signal extraction procedure is optimized by including a kinematic fit of the Wt signal and studying only subsets of events that have a cleaner event topology. These consist of events that contain a hadronically decaying top quark or events in which the light-quark jets are matched to truth particles from the Monte Carlo information. The expected signal significance, including systematic uncertainties was evaluated.