Measurement of the top quark pair production cross section in the single-lepton channel with ATLAS in proton-proton collisions at 8 TeV using kinematic fits with b-tagging

A measurement of the top quark pair ( $t\bar{t}$ ) inclusive production cross section in $pp$ collisions at a centre-of-mass energy of $\sqrt{s}=8$ TeV is presented. Data were collected with the ATLAS detector at the CERN Large Hadron Collider. The analysis has been done in the lepton+jets final state in a data set corresponding to an integrated luminosity of 5.8 fb$^{-1}$. A multivariate technique and $b$-jet identification were employed to separate the signal $t\bar{t}$ events from the various backgrounds. The inclusive $t\bar{t}$ production cross section is measured to be $\sigma_{t\bar{t}} = 241 \pm 2$ (stat.) $\pm 31$ (syst.) $\pm 9$ (lumi.) pb and is in good agreement with the theoretical prediction $\sigma_{t\bar{t}}^{theor.} = 238^{+22}_{-24}$ pb.