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

• Published in: The European physical journal. C, Particles and fields Particles and fields, 2016-01, Vol.76 (1)
• Main Authors: Aad, G., Barnovska, Z., Berger, N., Delmastro, M., Di Ciaccio, L., Doan, T.K.O., Elles, S., Goy, C., Hryn’ova, T., Jézéquel, S., Koletsou, I., Lafaye, R., Leveque, J., Massol, N., Mastrandrea, P., Sauvage, G., Sauvan, E., Simard, O., Todorov, T., Wingerter-Seez, I., Yatsenko, E., Rahal, G ., Alio, L., Barbero, M., Coadou, Y., Diaconu, C., Diglio, Sara, Djama, F., Duccu, O., Feligioni, L., Gao, J., Hallewell, G.D., Hubaut, F., Kahn, S.J., Knoops, E. B. F. G., Le Guirriec, E., Liu, J., Liu, K., Madaffari, D., Mochizuki, K., Monnier, E., Muanza, S., Nagai, Y., Nagy, E., Pralavorio, P., Rozanov, A., Serre, T., Talby, M., Ticse Torres, R.E., Tiouchichine, E., Tisserant, S., Toth, J., Touchard, F., Vacavant, L., Albrand, S., Collot, J., Crépé-Renaudin, S., Delsart, P.A., Gabaldon, C., Genest, M.H., Hostachy, J.Y., Ledroit-Guillon, F., Lleres, A., Lucotte, A., Malek, F., Monini, C., Stark, J., Trocmé, B., Wu, M., Ayoub, M.K., Bassalat, A., Bécot, C., Binet, S., Bourdarios, C., Delgove, D., de Vivie de Regie, J.-B., Duflot, L., Escalier, M., Fayard, L., Fournier, D., Gkougkousis, E.L., Grivaz, J-F., Guillemin, T., Hariri, F., Henrot-Versille, S., Hrivnac, J., Iconomidou-Fayard, L., Kado, M., Lounis, A., Makovec, N., Morange, N., Nellist, C., Petroff, P., Poggioli, L., Puzo, P., Renaud, A., Rousseau, D., Rybkin, G., Schaffer, A.C., Scifo, E.
• Format: Article
• Language: English
• Subjects: High Energy Physics - Experiment; Physics; PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
• ISSN: 1434-6044; 1434-6052
• DOI: 10.1140/epjc/s10052-015-3852-4

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 predictions.