Search for single top quark production through FCNC at ATLAS experiment

Flavour changing neutral currents (FCNC) are strongly suppressed in the Standard Model (SM). Although absent at tree level, small FCNC contributions are expected at one-loop level. For the top quark, the expected FCNC branching fractions to gauge bosons, e.g. $t\rightarrow q$+gluon, are predicted to be at the level of $10^{-13}$~\cite{Eilam:1990zc}. There are, howevre, extensions of the SM which predict the presence of FCNC contributions and significantly enhance the FCNC rates compared to the SM predictions. ATLAS has studied direct single top-quark production through FCNC $qg\rightarrow t\rightarrow bW$~\cite{Alhroob:1329491}, where the u(c) quark interacts with a gluon to produce a single top quark, and then top quark decays via SM process, $t\rightarrow W+b$.