Dortmund 2021 – scientific programme

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T: Fachverband Teilchenphysik

T 79: Top quark production III

T 79.5: Talk

Thursday, March 18, 2021, 17:00–17:15, Td

Z boson reconstruction in ttZ final states with four charged leptons using deep neural networks at 13 TeV with the ATLAS detector — Steffen Korn, Arnulf Quadt, •Tomke Schröer, Elizaveta Shabalina, and Knut Zoch — II. Physikalisches Institut, Georg-August-Universität Göttingen

The production of a top quark in association with a Z boson gives access to the electroweak coupling between the top quark and the Z boson, which provides sensitivity to the third component of the top-quark’s weak isospin. In the tetralepton channel, the Z boson and both top quarks decay leptonically. This channel is of major interest as it comes with a high signal purity. In this talk, the application of a deep neural network for the reconstruction of the Z boson is presented. The reconstruction includes the correct assignment of the leptons originating from the Z boson and the origin of the Z boson itself. This is an important aspect since it provides access to the t–Z system. When the Z boson is emitted by one of the top quarks, the structure and strength of the coupling between the top quark and the Z boson can be probed within the framework of the Standard Model Effective Field Theory (SMEFT). Deviations from the Standard Model (SM) prediction would indicate physics beyond the SM.