Measurement of the tt̄W and tt̄Z production cross sections in multilepton final states using 3.2 fb−¹ of pp collisions at s√ = 13 TeV with the ATLAS detector

A measurement of the ttZ and ttW production cross sections in final states with either two same-charge muons, or three or four leptons (electrons or muons) is presented. The analysis uses a data sample of proton-proton collisions at s √ =13 TeV recorded with the ATLAS detector at the Large Hadron Collider in 2015, corresponding to a total integrated luminosity of 3.2 fb −1 . The inclusive cross sections are extracted using likelihood fits to signal and control regions, resulting in σ ttZ =0.9±0.3 pb and σ ttW =1.5±0.8 pb, in agreement with the Standard Model predictions.