Measurement of the Inclusive and Fiducial tt̅ Production Cross-Sections in the Lepton + Jets Channel in pp Collisions at √s=8 TeV with the ATLAS Detector


The inclusive and fiducial tt̅ 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 tt̅ cross-section is measured with a precision of 5.7% to be σ_{inc} (tt̅) = 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 σ_{fid}(tt̅) = 48.8 ± 0.1 (stat.) ± 2.0 (syst.) ± 0.9 (lumi.) pb with a precision of 4.5%.



Partons, Hadron colliders, Large Hadron Collider (France and Switzerland), Mass (Physics), Proton-proton interactions


CC BY 4.0 (Attribution), ©2018 CERN, for the ATLAS Collaboration