UC Irvine

A measurement of the tt¯Z$$t\bar{t}Z$$ and tt¯W$$t\bar{t}W$$ 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 s=13$$\sqrt{s} = 13$$ TeV recorded with the ATLAS detector at the Large Hadron Collider in 2015, corresponding to a total integrated luminosity of 3.2 fb-1$$^{-1}$$. The inclusive cross sections are extracted using likelihood fits to signal and control regions, resulting in σtt¯Z=0.9±0.3$$\sigma _{t\bar{t}Z} = 0.9 \pm 0.3$$ pb and σtt¯W=1.5±0.8$$\sigma _{t\bar{t}W} = 1.5 \pm 0.8$$ pb, in agreement with the Standard Model predictions.