Aad, G.Aakvaag, E.Abbott, B.Abdelhameed, S.Abeling, K.Abicht, N.J.Abidi, S.H.Aboelela, M.Aboulhorma, A.Abramowicz, H.Abreu, H.Abulaiti, Y.Acharya, B.S.Ackermann, A.Adam Bourdarios, C.Adamczyk, L.Addepalli, S.V.Addison, M.J.Adelman, J.Adiguzel, A.et al.2025-08-252025-08-252025Physics Letters B, 2025; 860:139177-1-139177-280370-26930370-2693https://hdl.handle.net/2440/147057Inclusive cross-sections for top-quark pair production in association with charm quarks are measured with proton-proton collision data at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of 140 fb−1, collected with the ATLAS experiment at the LHC between 2015 and 2018. The measurements are performed by requiring one or two charged leptons (electrons and muons), two 𝑏-tagged jets, and at least one additional jet in the final state. A custom flavor-tagging algorithm is employed for the simultaneous identification of 𝑏-jets and 𝑐-jets. In a fiducial phase space that replicates the acceptance of the ATLAS detector, the cross-sections for 𝑡𝑡̄+ ≥2𝑐 and 𝑡𝑡̄+ 1𝑐 production are measured to be 1.28+0.27 −0.24 pb and 6.4+1.0 −0.9 pb, respectively. The measurements are primarily limited by uncertainties in the modeling of inclusive 𝑡𝑡̄ and 𝑡𝑡̄+ 𝑏𝑏̄ production, in the calibration of the flavor-tagging algorithm, and by data statistics. Cross-section predictions from various 𝑡𝑡̄ simulations are largely consistent with the measured cross-section values, though all underpredict the observed values by 0.5 to 2.0 standard deviations. In a phase-space volume without requirements on the 𝑡𝑡̄ decay products and the jet multiplicity, the cross-section ratios of 𝑡𝑡̄ + ≥2𝑐 and 𝑡𝑡̄ + 1𝑐 to total 𝑡𝑡̄ + jets production are determined to be (1.23 ± 0.25)% and (8.8±1.3)%.en© 2024 CERN for the beneϧt of the ATLAS Collaboration. Published by Elsevier B.V. Funded by SCOAP³. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).top-quark pair productionJournal article10.1016/j.physletb.2024.139177723105