Karlsruhe 2024 – scientific programme
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T: Fachverband Teilchenphysik
T 103: Top physics 4 (tt+X)
T 103.2: Talk
Thursday, March 7, 2024, 16:15–16:30, Geb. 30.95: Audimax
Classification of tt+X (heavy flavour) processes at the CMS experiment — •Rufa Kunnilan Muhammed Rafeek1, Ulrich Husemann1, Emanuel Pfeffer1, Jan van der Linden2, and Michael Wassmer1 — 1Institute of Experimental Particle Physics (ETP), Karlsruhe Institute of Technology (KIT) — 2Institute of Experimental Particle Physics and Gravity, Ghent University (BE)
Top quark - antiquark pairs (tt) produced in association with other particles (X) where X can be the Higgs boson, Z/W boson or QCD-initiated heavy flavour jets (bb/cc), plays a significant role in experimental studies at the LHC.
The analysis is challenging as these processes, particularly when the bosons decay into heavy flavour quarks, like for example, tt+H (H→ bb) and tt+bb or tt+Z (Z→ bb), share the same signature and kinematic features. These high jet multiplicity final states create ambiguities in the reconstruction and identification of these processes and thus, it is hard to differentiate them from each other.
The complex task of simultaneously measuring these tt+X processes is made by exploring advanced machine learning techniques such as Graph Neural Networks. The primary objective is to distinguish the additional heavy flavour jets, treated as a binary classification task, from the one originating in the tt-system. This differentiation is crucial for subsequent multi-class event classification, encompassing categories such as tt+bb, tt+H (bb), tt+Z (bb) and tt+cc.
In this talk the current status of such a measurement for the separation of these events, using the tt single lepton channel is presented.
Keywords: Top quark, heavy flavour quarks; ttbar; GNNs