G. Aad, B. Abbott, D. C. Abbott, K. Abeling, B. Ali, K. Augsten, B. Bergmann, T. Billoud, M. Havránek, Z. Hubáček et al.: Observation of Single-Top-Quark Production in Association with a Photon Using the ATLAS Detector. Physical Review Letters 131(18), 181901 (2023). doi:10.1103/PhysRevLett.131.181901