Search for single top-quark production via FCNC in strong interaction in $\sqrt{s}=8\,\,\mathrm{TeV}$ ATLAS data

Results with 2012 data on the search for single top-quark production via flavour changing neutral currents (FCNCs) in strong interactions are presented. Data collected with the ATLAS detector in 2012 at a centre-of-mass energy of $\sqrt{s}=8\,\,\mathrm{TeV}$ and corresponding to an integrated luminosity of $\mathcal{L}_{\mathrm{int}} =14.2\,\,\mathrm{fb^{-1}}$ is used. It is searched for FCNC events in which a light quark ($u$ or $c$) interacts with a gluon to produce a single top-quark, either with or without the associated production of another light quark or gluon. Candidate events of top quarks decaying into leptons and jets are selected and classified into signal- and background-like events using a neural network. As no signal is observed in the neural network output distributions, a new upper limit on the production cross-sections multiplied by the $t \rightarrow Wb$ branching fraction is set. The observed 95% C.L. limit is found at $\sigma_{qg\to t} \times {\cal B} (t \to bW)<2.5\,\,\mathrm{pb}$ can be converted into upper limits on the coupling constants of the involved FCNC interactions $\kappa_{ugt}/\Lambda < 5.1\cdot 10^{-3}\,\,\mathrm{TeV}^{-1}$ and $\kappa_{cgt}/\Lambda < 1.1\cdot 10^{-2}\,\,\mathrm{TeV}^{-1}$ and on the branching fractions ${\cal B}(t \rightarrow ug) < 3.1\cdot 10^{-5}$ and ${\cal B}(t \rightarrow cg) < 1.6\cdot 10^{-4}$.