Abstract:
This Letter reports the observation of single top quarks produced together with a photon using 139 fb−1 of 13 TeV proton-proton collision data collected with the ATLAS detector at the Large Hadron Collider. The analysis uses the presence of a forward jet, characteristic of t-channel production, and separates the signal from the background with neural networks. Requiring a photon with transverse momentum larger than 20 GeV and within the detector acceptance, the fiducial cross section is measured to be 688 ± 23 (stat.) +75−71 (syst.) fb, to be compared with the Standard Model prediction of 515 +36−42 fb at next-to-leading order in QCD.

To the paper:  
arXiv:[2302.01283]

Our other publications on the subject of particle physics can be found on the corresponding list of publications.