Search for FCNC in top-quark events in ATLAS

Searches for flavor changing neutral current (FCNC) processes in top-quark production and decays by the ATLAS Collaboration are presented. Data collected from $pp$ collisions at the LHC at a centre-of-mass energy of 7 TeV during 2011, corresponding to an integrated luminosity of 2.05/fb, are used. In a first analysis single top-quarks produced via FCNC are searched for. Candidate events with a semileptonic top-quark decay signature are classified as signal or background-like events by using several kinematic variables as input to a neural network. No signal is observed in the neural network output distribution and a Bayesian upper limit is placed on the production cross-section. The observed upper limit is converted using a model-independent approach into upper limits on the coupling strengths k_{ugt}/Lambda ug) cg) Zq FCNC (q=u,c) channel, and the other through the Standard Model dominant mode t-->Wb. Only the decays of the Z boson to charged leptons and leptonic W-boson decays are considered as signal. No evidence for an FCNC signal is found and thus an upper limit on the t-->Zq branching ratio of BF(t-->Zq)