PT Journal AU ATLAS Collaboration (Aad, Gea Amos, KR Aparisi Pozo, JA Bailey, AJ Bouchhar, N Cabrera Urban, S Cantero, J Cardillo, F Castillo Gimenez, V Chitishvili, M Costa, MJ Didenko, M Escobar, C Fiorini, L Fullana Torregrosa, E Fuster, J Garcia, C Garcia Navarro, JE Gomez Delegido, AJ Gonzalez de la Hoz, S Gonzalvo Rodriguez, GR Guerrero Rojas, JGR Higon-Rodriguez, E Lacasta, C Lozano Bahilo, JJ Marti-Garcia, S Martinez Agullo, P Miralles Lopez, M Mitsou, VA Monsonis Romero, L Moreno Llacer, M Munoz Perez, D Navarro-Gonzalez, J Poveda, J Prades Ibañez, A Rubio Jimenez, A Ruiz-Martinez, A Sabatini, P Salt, J Sanchez Sebastian, V Sayago Galvan, I Senthilkumar, V Soldevila, U Sanchez, J Torro Pastor, E Valero, A Valls Ferrer, JA Varriale, L Villaplana Perez, M Vos, M TI Measurement of the charge asymmetry in top-quark pair production in association with a photon with the ATLAS experiment SO Physics Letters B JI Phys. Lett. B PY 2023 BP 137848 EP 21pp VL 843 DI 10.1016/j.physletb.2023.137848 AB A measurement of the charge asymmetry in top-quark pair (tt¯) production in association with a photon is presented. The measurement is performed in the single-lepton tt¯ decay channel using proton-proton collision data collected with the ATLAS detector at the Large Hadron Collider at CERN at a centre-of-mass-energy of 13 TeV during the years 2015-2018, corresponding to an integrated luminosity of 139 fb−1. The charge asymmetry is obtained from the distribution of the difference of the absolute rapidities of the top quark and antiquark using a profile likelihood unfolding approach. It is measured to be AC=−0.003±0.029 in agreement with the Standard Model expectation. ER