Search for flavour-changing neutral currents in processes with one top quark and a photon using 81 fb−1of ppcollisions at √s=13 TeV with the ATLAS experiment Aad, G. Aguilar Saavedra, Juan Antonio Atlas Collaboration A search for flavour-changing neutral current (FCNC) events via the coupling of a top quark, a photon, and an up or charm quark is presented using 81 fb−1of 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 tγproduction 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 tγproduction 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). 2020-01-24T08:01:56Z 2020-01-24T08:01:56Z 2019-11-13 info:eu-repo/semantics/article Aad, G., Abbott, B., Abbott, D. C., Abud, A. A., Abeling, K., Abhayasinghe, D. K., ... & Abreu, H. (2020). Search for flavour-changing neutral currents in processes with one top quark and a photon using 81 fb− 1 of pp collisions at root s= 13TeV with the ATLAS experiment. Physics Letters B, 800, 135082. http://hdl.handle.net/10481/59095 10.1016/j.physletb.2019.135082 eng http://creativecommons.org/licenses/by/3.0/es/ info:eu-repo/semantics/openAccess Atribución 3.0 España Elsevier BV