Measurement of the t(t)over-bar production cross-section using e mu events with b-tagged jets in pp collisions at root s=13 TeV with the ATLAS detector

M. Aaboud, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, B Abeloos, R. Aben, O.S. AbouZeid, NL Abraham, H. Abramovic, Mogens Dam, Jørn Dines Hansen, Jørgen Beck Hansen, Stefania Xella, Peter Henrik Hansen, Troels Christian Petersen, Lotte Ansgaard Thomsen, Almut Maria Pingel, Ask Emil Løvschall-Jensen, Alejandro Alonso DiazJames William Monk, Lars Egholm Pedersen, Graig Wiglesworth, Gorm Aske Gram Krohn Galster

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Abstract

This paper describes a measurement of the inclusive top quark pair production cross-section (σtt¯) with a data sample of 3.2fb−1 of proton–proton collisions at a centre-of-mass energy of s=13TeV, collected in 2015 by the ATLAS detector at the LHC. This measurement uses events with an opposite-charge electron–muon pair in the final state. Jets containing b-quarks are tagged using an algorithm based on track impact parameters and reconstructed secondary vertices. The numbers of events with exactly one and exactly two b-tagged jets are counted and used to determine simultaneously σtt¯ and the efficiency to reconstruct and b-tag a jet from a top quark decay, thereby minimising the associated systematic uncertainties. The cross-section is measured to be: σtt¯=818±8(stat)±27(syst)±19(lumi)±12(beam) pb, where the four uncertainties arise from data statistics, experimental and theoretical systematic effects, the integrated luminosity and the LHC beam energy, giving a total relative uncertainty of 4.4%. The result is consistent with theoretical QCD calculations at next-to-next-to-leading order. A fiducial measurement corresponding to the experimental acceptance of the leptons is also presented.

OriginalsprogEngelsk
TidsskriftPhysics Letters B
Vol/bind761
Sider (fra-til)136-157
ISSN0370-2693
DOI
StatusUdgivet - 10 okt. 2016

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