Measurement of the $${\varvec{t\bar{t}Z}}$$ t t ¯ Z and $${\varvec{t\bar{t}W}}$$ t t ¯ W production cross sections in multilepton final states using 3.2 fb $$^{-1}$$ - 1 of $$\varvec{pp}$$ p p collisions at $$\sqrt{s}$$ s = 13 TeV with the ATLAS detector

A measurement of the $$t\bar{t}Z$$ and $$t\bar{t}W$$ 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 $$\sqrt{s} = 13$$ 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 $$\sigma _{t\bar{t}Z} = 0.9 \pm 0.3$$  pb and $$\sigma _{t\bar{t}W} = 1.5 \pm 0.8$$  pb, in agreement with the Standard Model predictions.