Measurement of the Charge Asymmetry in Top Quark Pair Production

We present a measurement of the charge asymmetry in top quark pair production using an integrated luminosity of $1.09\,\mathrm{fb}^{-1}$ collected with the CMS detector. Top quark pairs with a signature of one electron or muon and four or more jets, at least one of them $b$ tagged, are selected. At LHC a small charge asymmetry in the rapidity distributions of top and antitop quark is predicted, with a slightly broader rapidity distribution for top quarks, while antitop quarks are produced more centrally and therefore possess a narrower rapidity distribution. We use two different sensitive variables, one based on pseudorapidities ($\eta$) of the two top quarks and one based on rapidities ($y$). The measured charge asymmetries of $A_{C}^{\eta} = -0.016 \pm 0.030~(\mathrm{stat.})^{+0.010}_{-0.019}~(\mathrm{syst.})$ and $A_{C}^{y} = -0.013 \pm 0.026~(\mathrm{stat.})^{+0.026}_{-0.021}~(\mathrm{syst.})$ are within the uncertainties consistent with the small positive asymmetries predicted by the Standard Model.