Karlsruhe 2024 – scientific programme

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T: Fachverband Teilchenphysik

T 103: Top physics 4 (tt+X)

T 103.4: Talk

Thursday, March 7, 2024, 16:45–17:00, Geb. 30.95: Audimax

Inclusive cross-section measurements of top-quark pair production in association with charm quarks with the ATLAS experiment — •Matthew Kingston, Arnulf Quadt, and Elizaveta Shabalina — II. Physikalisches Institut, Georg-August-Universität Göttingen

The production of top-quark pairs in association with charm quarks is an irreducible background to rare final states such as ttH and tttt, as well as being a particular challenge for QCD modelling due to the uncertainties in the choice of factorisation and renormalisation scales. The first ATLAS measurement of the inclusive total and fiducial cross-section of this process is performed using data corresponding to an integrated luminosity of 140 fb⁻¹, collected by the ATLAS experiment at the LHC between 2015 and 2018 at a centre-of-mass energy of 13 TeV. Measurements are performed in both the dileptonic and semi-leptonic channels, and their combination. A custom heavy-flavour tagging algorithm is used to distinguish jets originating from b and c quarks, based on the standard ATLAS DL1r tagger. This presentation will focus on the work done to understand systematic uncertainties. The measurements of the cross-section as well as of the ratio of tt + ≥2c and tt + 1c production over inclusive production of tt+jets are compared with predictions of the state-of-the-art NLO+PS Monte Carlo simulations of tt production.