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

Abstract

The inclusive and fiducial 𝑡𝑡¯ production cross-sections are measured in the lepton+jets channel 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%.