# Measurement of top quark-antiquark pair production in association with a W or Z boson in pp collisions at s√=8 TeV

CMS Collaboration; Khachatryan, V; Sirunyan, A M; Tumasyan, A; Amsler, C; Canelli, F; Chiochia, V; De Cosa, A; Hinzmann, A; Hreus, T; Lange, C; Kilminster, B; Ngadiuba, J; Robmann, P; Ronga, F J; Taroni, S; Verzetti, M; Yang, Y; Mejias, B; et al (2014). Measurement of top quark-antiquark pair production in association with a W or Z boson in pp collisions at s√=8 TeV. European Physical Journal C - Particles and Fields, 74(3060):online.

## Abstract

A measurement of the cross section for the production of top quark–antiquark pairs ( tt⎯ ) in association with a vector boson V (W or Z) in proton-proton collisions at s√=8 TeV is presented. The results are based on a dataset corresponding to an integrated luminosity of 19.5 fb−1 recorded with the CMS detector at the LHC. The measurement is performed in three leptonic (e and μ) channels: a same-sign dilepton analysis targeting tt⎯W events, and trilepton and four-lepton analyses designed for tt⎯Z events. In the same-sign dilepton channel, the tt⎯W cross section is measured as σtt⎯W=170+90−80(stat)±70(syst)fb , corresponding to a significance of 1.6 standard deviations over the background-only hypothesis. Combining the trilepton and four-lepton channels, a direct measurement of the tt⎯Z cross section, σtt⎯Z=200+80−70(stat)+40−30(syst)fb−1 , is obtained with a significance of 3.1 standard deviations. The measured cross sections are compatible with standard model predictions within their experimental uncertainties. The inclusive tt⎯V process is observed with a significance of 3.7 standard deviations from the combination of all three leptonic channels.

## Abstract

A measurement of the cross section for the production of top quark–antiquark pairs ( tt⎯ ) in association with a vector boson V (W or Z) in proton-proton collisions at s√=8 TeV is presented. The results are based on a dataset corresponding to an integrated luminosity of 19.5 fb−1 recorded with the CMS detector at the LHC. The measurement is performed in three leptonic (e and μ) channels: a same-sign dilepton analysis targeting tt⎯W events, and trilepton and four-lepton analyses designed for tt⎯Z events. In the same-sign dilepton channel, the tt⎯W cross section is measured as σtt⎯W=170+90−80(stat)±70(syst)fb , corresponding to a significance of 1.6 standard deviations over the background-only hypothesis. Combining the trilepton and four-lepton channels, a direct measurement of the tt⎯Z cross section, σtt⎯Z=200+80−70(stat)+40−30(syst)fb−1 , is obtained with a significance of 3.1 standard deviations. The measured cross sections are compatible with standard model predictions within their experimental uncertainties. The inclusive tt⎯V process is observed with a significance of 3.7 standard deviations from the combination of all three leptonic channels.

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