Search for flavour-changing neutral currents in processes with one top quark and a photon using 81 fb−1 of pp collisions at √s = 13 TeV with the ATLAS experiment
Date of Archiving2020
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High Energy Physics
Experimental High Energy Physics
Key wordsHigh Energy Physics; Experiment
A search for flavour-changing neutral current events via the coupling of a top quark, a photon, and an up or charm quark is presented using 81fb−1 of proton-proton collision data taken at a centre-of-mass energy of 13 TeV with the ATLAS detector at the LHC. Events with a photon, an electron or muon, a b-tagged jet, and missing transverse momentum are selected. A neural network based on kinematic variables differentiates between events from signal and background processes. The data are consistent with the background-only hypothesis, and limits are set on the strength of the tqγ coupling in an effective field theory. These are also interpreted as 95 % CL upper limits on the cross section for FCNC tγ production via a left-handed (right-handed) tuγ coupling of 36 fb (78 fb) and on the branching ratio for t→γu of 2.8×10−5 (6.1×10−5). In addition, they are interpreted as 95 % CL upper limits on the cross section for FCNC tγ production via a left-handed (right-handed) tcγ coupling of 40 fb (33 fb) and on the branching ratio for t→γc of 22×10−5 (18×10−5 ).