Measurement of the charge asymmetry in dileptonic $t\bar{t}$ events with the ATLAS detector at $\sqrt{s} = 7$ TeV

A measurement of the top-antitop ($t\bar{t}$) charge asymmetry is presented using data corresponding to an integrated luminosity of 4.6 \mbox{fb$^{-1}$} of LHC $pp$ collisions at a centre-of-mass energy of 7 \textrm{Te\kern -0.1em V} collected by the ATLAS detector. Events with two charged leptons, at least two jets and missing transverse momentum are selected. Two charge asymmetry observables are studied, based on the identified charged leptons, $A^{\ell\ell}_{\textrm{C}}$, or on the reconstructed $t\bar{t}$ final state, $A^{t\bar{t}}_{\textrm{C}}$. The asymmetries are measured to be: \begin{eqnarray*} A^{\ell\ell}_{\textrm{C}} & = & 0.024 \pm 0.015 \mbox{$\;$(stat.)} \pm 0.009 \mbox{$\;$(syst.)}, \end{eqnarray*} \begin{eqnarray*} A^{t\bar{t}}_{\textrm{C}} & = & 0.021 \pm 0.025 \mbox{$\;$(stat.)} \pm 0.017 \mbox{$\;$(syst.)}. \end{eqnarray*} The measured values are in agreement with the Standard Model predictions.