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arXiv · 1509.05276

Measurement of the $t\bar{t}W$ and $t\bar{t}Z$ production cross sections in $pp$ collisions at $\sqrt{s} = 8 \mathrm{\ Te\kern -0.1em V}$ with the ATLAS detector

ATLAS Collaboration
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Abstract

The production cross sections of top-quark pairs in association with massive vector bosons have been measured using data from $pp$ collisions at $\sqrt{s} = 8 \mathrm{\ Te\kern -0.1em V}$. The dataset corresponds to an integrated luminosity of $20.3\ \mathrm{fb}^{-1}$ 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 $t\bar{t}W$ and $t\bar{t}Z$ processes simultaneously yields a significance of $5.0σ$ ($4.2σ$) over the background-only hypothesis for $t\bar{t}W$ ($t\bar{t}Z$) production. The measured cross sections are $σ_{t\bar{t}W} = 369^{+100}_{-91}$ fb and $σ_{t\bar{t}Z} = 176^{+58}_{-52}$ fb. The background-only hypothesis with neither $t\bar{t}W$ nor $t\bar{t}Z$ production is excluded at $7.1σ$. All measurements are consistent with next-to-leading-order calculations for the $t\bar{t}W$ and $t\bar{t}Z$ processes.

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ATLAS Collaboration. 2015-12-09. Measurement of the $t\bar{t}W$ and $t\bar{t}Z$ production cross sections in $pp$ collisions at $\sqrt{s} = 8 \mathrm{\ Te\kern -0.1em V}$ with the ATLAS detector. https://doi.org/10.1007/jhep11(2015)172

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