Abstract

his paper describes a measurement of the inclusive top quark pair production cross-section (sigma(t (t) over bar)) with a data sample of 3.2 fb(-1) of proton-proton collisions at a centre-of-mass e ...

Highlights

  • The top quark is the heaviest known fundamental particle, with a mass mt which is much larger than any of the other quarks, and close to the scale of electroweak symmetry breaking

  • 13 TeV pp collisions recorded by the ATLAS detector at the LHC

  • Assuming a top quark mass of mt = 172.5 GeV, the result is: σtt = 818 ± 8 ± 27 ± 19 ± 12 pb, where the four uncertainties are due to data statistics, experimental and theoretical systematic effects, the integrated luminosity and the LHC beam energy, giving a total relative uncertainty of 4.4%

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Summary

Introduction

The top quark is the heaviest known fundamental particle, with a mass mt which is much larger than any of the other quarks, and close to the scale of electroweak symmetry breaking. Calculations of the ttproduction cross-section at hadron colliders are available at full next-to-next-to-leading-order (NNLO) accuracy in the strong coupling constant αS, including the resummation of next-to-next-to-leading logarithmic (NNLL) soft gluon terms [1,2,3,4,5]. In this pape√r a reference value of 832+−4406 pb at a centre-of-mass energy of s = 13 TeV assuming mt = 172.5 GeV is used, corresponding to a relative precision of +−45..85%. Powheg-Box v2 + Pythia Powheg-Box v2 + Herwig++ Madgraph5_aMC@NLO + Herwig++ Powheg-Box v1 + Pythia Powheg-Box v1 + Herwig++ Sherpa 2.1.1 Sherpa 2.1.1 Powheg + Pythia Powheg-Box v1 + Pythia Powheg-Box v2 + Pythia MadGraph + Pythia

Data and simulation samples
Object and event selection
Extraction of the ttcross-section
Background estimation
Systematic uncertainties
Results and conclusions
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