This talk presents the ATLAS Collaboration’s first measurement of the inclusive cross-section for top-quark pair production in association with charm quarks. Using the full Run~2 proton–proton collision data sample at s = 13\, TeV s = 13 TeV, collected with the ATLAS experiment at the LHC between 2015 and 2018, the measurement selects tt t t ‾ events with one or two charged leptons and at least one additional jet in the final state. A custom flavour-tagging algorithm is employed to simultaneously identify b b -jets and c c -jets. The fiducial cross-sections for tt+≥2c t t ‾ + ≥ 2 c and tt+1c t t ‾ + 1 c production are found to largely agree with predictions from various tt t t ‾ simulations, though all underpredict the observed values.
Knut Zoch (Thu,) studied this question.