Aachen 2019 – scientific programme

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T: Fachverband Teilchenphysik

T 30: Suche nach Neuen Teilchen II

T 30.9: Talk

Tuesday, March 26, 2019, 18:00–18:15, H07

Search for heavy resonances decaying into tt in the fully hadronic final state with the ATLAS full Run-2 dataset — Katharina Behr, •Yu-Heng Chen, and Klaus Mönig — Deutsches Elektronen-Synchrotron, Hamburg and Zeuthen, Germany

Heavy resonances decaying into a top-antitop quark pair (tt), such as a heavy gauge boson Z′, are predicted by many extensions of the Standard Model.

We analyse the full dataset recorded by the ATLAS experiment during the second run of the LHC to search for resonances at the high-mass frontier that decay to tt. In this kinematic region, the decay products of each top quark are highly collinear and form a single hadronic jet with a characteristic substructure.

Top-tagging using machine learning techniques as well as b-tagging in a very busy environment are studied and further optimised to better suppress the challenging multijets background while retaining reasonably good signal efficiency. In addition, for the first time in this final state, the background spectrum is estimated using data-driven techniques by a functional form fit to data in order to reduce the impact of limited Monte Carlo (MC) statistics in the high tt mass region. Several ways for signal interpolation are also introduced to obtain a finer signal grid to reduce the need for computing-time intensive Monte Carlo simulations.