CMS collaboration (2307 authors)Hollar, JonathanCalpas, BettyNayak, ArunaBargassa, PedrameBeirão Da Cruz E Silva, CristóvãoDi Francesco, AgostinoFaccioli, PietroFerreira Parracho, Pedro GuilhermeGallinaro, MicheleLeonardo, NunoLloret Iglesias, LaraNguyen, FedericoRodrigues Antunes, JoaoSeixas, JoaoToldaiev, OleksiiVadruccio, DanieleVarela, JoaoVischia, PietroDavid Tinoco Mendes, AndreSilva, PedroMusella, PasqualePela, Joao2019-02-042019-02-042016-01-18http://dx.doi.org/10.1007/JHEP01(2016)096http://hdl.handle.net/10400.26/26946Measurements of the cross sections for top quark pairs produced in association with a W or Z boson are presented, using 8 TeV pp collision data corresponding to an integrated luminosity of 19.5 fb$^{−1}$, collected by the CMS experiment at the LHC. Final states are selected in which the associated W boson decays to a charged lepton and a neutrino or the Z boson decays to two charged leptons. Signal events are identified by matching reconstructed objects in the detector to specific final state particles from $ \mathrm{t}\overline{\mathrm{t}}\mathrm{W} $ or $ \mathrm{t}\overline{\mathrm{t}}\mathrm{Z} $ decays. The $ \mathrm{t}\overline{\mathrm{t}}\mathrm{W} $ cross section is measured to be 382$_{− 102}^{+ 117}$ fb with a significance of 4.8 standard deviations from the background-only hypothesis. The $ \mathrm{t}\overline{\mathrm{t}}\mathrm{Z} $ cross section is measured to be 242$_{− 55}^{+ 65}$ fb with a significance of 6.4 standard deviations from the background-only hypothesis. These measurements are used to set bounds on five anomalous dimension-six operators that would affect the $ \mathrm{t}\overline{\mathrm{t}}\mathrm{W} $ and $ \mathrm{t}\overline{\mathrm{t}}\mathrm{Z} $ cross sections.engjournal article2019-02-04