ATLAS collaboration (3035 authors)Aguilar-Saavedra, Juan AntonioAmaral, PedroAnjos, NunoCarvalho, JoãoCastro, Nuno FilipeConde Muiño, PatriciaDo Valle Wemans, AndréFiolhais, MiguelGomes, AgostinhoGonçalo, RicardoJorge, PedroLopes, LourencoMachado Miguens, JoanaMaio, AméliaManeira, JoséOliveira, Miguel AlfonsoOnofre, AntónioPalma, AlbertoPina, João AntonioPinto, BelmiroSantos, HelenaSaraiva, JoãoSilva, JoséSoares, MaraVeloso, FilipeWolters, Helmut2019-02-032019-02-032013-07-16http://dx.doi.org/10.1016/j.physletb.2012.05.022http://hdl.handle.net/10400.26/26117Results on the search for flavor-changing neutral-current single top-quark production are reported. Data collected with the ATLAS detector at a center-of-mass energy of sqrt(s) = 7 TeV and corresponding to an integrated luminosity of 2.05 fb^-1 are used. Candidate events with a leptonic top-quark decay signature are classified into signal- and background-like events using a neural network. No signal is observed in the output distribution and a Bayesian upper limit on the production cross-section is placed. The observed 95% C.L. upper limit on the cross-section multiplied by the t -> Wb branching fraction is measured to be sigma(qg -> t) x B(t -> Wb) < 3.9 pb. This upper limit can be converted into an upper limit of the coupling strength k_ugt/Lambda < 6.9 x 10^-3 TeV^-1 and k_cgt/Lambda < 1.6 x 10^-2 TeV^-1 and on the branching fractions B(t -> ug) < 5.7 x 10^-5 and B(t -> cg) < 2.7 x 10^-4.engjournal article2019-02-03