Fiducial cross-sections for tt¯ 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 tt¯ events with at least one additional b -jet is measured to be 950 ± 70 (stat.) -190+240 (syst.) fb in the lepton-plus-jets channel and 50 ± 10 (stat.) -10+15 (syst.) fb in the eμ channel. The cross-section times branching ratio for events with at least two additional b -jets is measured to be 19.3 ± 3.5 (stat.) ± 5.7 (syst.) fb in the dilepton channel ( eμ , μμ , and ee ) using a method based on tight selection criteria, and 13.5 ± 3.3 (stat.) ± 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 ± 0.33 (stat.) ± 0.28 (syst.)% for the ratio of tt¯ production with two additional b -jets to tt¯ production with any two additional jets. All measurements are in good agreement with recent theory predictions.

Aad, G., Abbott, B., Abdallah, J., Abdinov, O., Aben, R., Abolins, M., et al. (2016). Measurements of Fiducial Cross-Sections for tt¯ Production With One or Two Additional b -Jets in pp Collisions at √s = 8 TeV Using the ATLAS Detector. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS, 76(1), 1-37 [10.1140/epjc/s10052-015-3852-4].

Measurements of Fiducial Cross-Sections for tt¯ Production With One or Two Additional b -Jets in pp Collisions at √s = 8 TeV Using the ATLAS Detector

F. Ceradini;B. Di Micco;R. Di Nardo;D. Orestano;F. Petrucci;D. Puddu;G. Salamanna;