Measurement of the tt̅W and tt̅Z Production Cross Sections in pp Collisions at √s̅=8 TeV with the ATLAS Detector


The production cross sections of top-quark pairs in association with massive vector bosons have been measured using data from pp collisions at √s̅ = 8 TeV. The dataset corresponds to an integrated luminosity of 20.3 fb⁻¹ collected by the ATLAS detector in 2012 at the LHC. Final states with two, three or four leptons are considered. A fit to the data considering the tt̅W and tt̅Z processes simultaneously yields a significance of 5.0σ (4.2σ) over the background-only hypothesis for tt̅W (tt̅Z) production. The measured cross sections are σ_{tt̅W} = 369_(-91)^(+100) fb and σ_{tt̅Z} = 176_{-52}^{+58} fb. The background-only hypothesis with neither tt̅W nor tt̅Z production is excluded at 7.1σ. All measurements are consistent with next-to-leading-order calculations for the tt̅W and tt̅Z processes.



Electroweak interactions, Hadrons--Scattering, Top quark models, Partons, Hadron colliders, Monte Carlo methods, Vertex functions


CC BY 4.0 (Attribution), ©2015 The Authors