Göttingen 2025 – wissenschaftliches Programm

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T: Fachverband Teilchenphysik

T 8: Top Physics I (tt+X)

T 8.4: Vortrag

Montag, 31. März 2025, 17:30–17:45, VG 1.103

Measurement of tt+X (heavy flavour) processes at the CMS experiment — •Rufa Kunnilan Muhammed Rafeek, Ulrich Husemann, and Emanuel Pfeffer — Institute of Experimental Par- ticle Physics (ETP), Karlsruhe Institute of Technology (KIT)

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(bb) and tt+bb or tt+Z(bb), share the same signature and very similar 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 addressed by exploring advanced ML techniques such as Graph Neural Networks. The primary objective is to distinguish the additional heavy flavour jets (not part of the tt-system). This differentiation is crucial for subsequent multi-class event classification, encompassing categories such as tt + bb, tt + (bb), tt + (bb) and tt + cc. Effectively, this involves two classification tasks: a binary classification to identify additional jets and a multi-class classification for event categorization, culminating in promising classification results for tt+X events. In this talk, an overview of the ongoing analysis, designed with the Run-2 data of the LHC using the tt single lepton channel, is given.