Dresden 2013 – scientific programme

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T: Fachverband Teilchenphysik

T 38: Top-Quarks: Single-Top 1

T 38.2: Talk

Tuesday, March 5, 2013, 17:00–17:15, HSZ-04

Search for Single Top Quark Production via Flavour Changing Neutral Currents in 8 TeV ATLAS data — •Conrad Friedrich — Deutsches Elektronen-Synchrotron (DESY), Zeuthen, Germany

In the Standard Model (SM) single top quarks are produced via charged current interactions with the W boson. Transitions between top quarks and other quark flavours mediated by neutral gauge bosons, so-called Flavour Changing Neutral Currents (FCNC), are forbidden at tree level and highly suppressed at higher orders due to the Glashow-Iliopoulos-Maiani (GIM) mechanism. However, there exist several new physics models, which significantly enhance their rate compared to the Standard Model predictions by allowing for FCNC interactions already at tree level and / or introducing new particles in higher order loop diagrams. Therefore any observation of such processes would be a strong indirect indicator for new physics.

In this analysis data collected with the ATLAS detector at a center-of-mass energy of √s=8 TeV are searched for FCNC events in which a light quark (u,c) interacts with a gluon to produce a single top quark with or without the associated production of another quark or gluon. Candidate events of top quarks decaying leptonically are selected and classified into signal- and background-like events using a neural network. If no signal is observed, new upper limits on the production cross-sections multiplied by the t→Wb branching fraction and the coupling strengths of the involved FCNC interactions can be placed.