Measurements of fiducial cross-sections for $t\bar{t}$ production with one or two additional b-jets in pp collisions at $\sqrt{s}$ =8 TeV using the ATLAS detector
英文:
Measurements of fiducial cross-sections for $t\bar{t}$ production with one or two additional b-jets in pp collisions at $\sqrt{s}$ =8 TeV using the ATLAS detector
Fiducial cross-sections for $t\bar{t} $ production with one or two additional b-jets are reported, using an integrated luminosity of 20.3 fb$^{-1}$ of proton–proton collisions at a centre-of-mass energy of 8 TeV at the Large Hadron Collider, collected with the ATLAS detector. The cross-section times branching ratio for $t\bar{t} $ events with at least one additional b-jet is measured to be 950 $\pm $ 70 (stat.)$^{+240-190}$ (syst.) fb in the lepton-plus-jets channel and 50 $\pm $ 10 (stat.)$^{+15-10}$ (syst.) fb in the $e \mu $ channel. The cross-section times branching ratio for events with at least two additional b-jets is measured to be 19.3 $\pm $ 3.5 (stat.) $\pm $ 5.7 (syst.) fb in the dilepton channel ( $e \mu $ , $\mu \mu $ , and ee) using a method based on tight selection criteria, and 13.5 $\pm $ 3.3 (stat.) $\pm $ 3.6 (syst.) fb using a looser selection that allows the background normalisation to be extracted from data. The latter method also measures a value of 1.30 $\pm $ 0.33 (stat.) $\pm $ 0.28 (syst.)% for the ratio of $t\bar{t}$ production with two additional b-jets to $t\bar{t}$ production with any two additional jets. All measurements are in good agreement with recent theory
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