UC Santa Cruz

A measurement is presented of the tt¯ inclusive production cross section in pp collisions at a center-of-mass energy of s=8 TeV using data collected by the ATLAS detector at the CERN Large Hadron Collider. The measurement was performed in the lepton+jets final state using a data set corresponding to an integrated luminosity of 20.3 fb−1. The cross section was obtained using a likelihood discriminant fit and b-jet identification was used to improve the signal-to-background ratio. The inclusive tt¯ production cross section was measured to be 260±1(stat)−23+22(stat)±8(lumi)±4(beam) pb assuming a top-quark mass of 172.5 GeV, in good agreement with the theoretical prediction of 253−15+13 pb. The tt¯→(e,μ)+jets production cross section in the fiducial region determined by the detector acceptance is also reported.