Measurement of the inclusive and fiducial t t ̄ production cross-sections in the lepton+jets channel in pp collisions at √s = 8TeV with the ATLAS detector

Abstract

Theinclusiveandfiducialtt ̄productioncross-sectionsaremeasuredinthelepton+jetschannel using 20.2 fb−1 of proton–proton collision data at a centre-of-mass energy of 8 TeV recorded with the ATLAS detector at the LHC. Major systematic uncertainties due to the modelling of the jet energy scale and b-tagging efficiency are constrained by separating selected events into three disjoint regions. In order to reduce systematic uncertainties in the most important background, the W + jets process is modelled using Z + jets events in a data-driven approach. The inclusive tt ̄ cross-section is measured with a precision of 5.7% to be σinc(tt ̄) = 248.3 ± 0.7 (stat.) ± 13.4 (syst.) ± 4.7 (lumi.) pb, assuming a top-quark mass of 172.5 GeV. The result is in agreement with the Standard Model prediction. The cross-section is also measured in a phase space close to that of the selected data. The fiducial cross-section is σfid(tt ̄) = 48.8 ± 0.1 (stat.) ± 2.0 (syst.) ± 0.9 (lumi.) pb with a precision of 4.5%.