Overview of the ttW process and its measurements by the ATLAS experiment

Production of $t\bar{t}$ in association with a W boson is a rare and massive signature at the LHC and is sensitive to new physics. It is also an important background for measurements of $t\bar{t}H$ and $t\bar{t}t\bar{t}$ in multi-lepton final states. Recent ATLAS measurements have observed production rates 40%-70% higher than expected at NLO+NNLL QCD and NLOPS. While a fully differential cross section measurement is needed to fully resolve these discrepancies, the $t\bar{t}W$ process can be a useful test bed for BSM physics modifying its QCD and EW contributions. This talk will present the results for a recent ATLAS measurement of the leptonic asymmetry in $t\bar{t}W$ events with three leptons. Asymmetries are extracted at the detector and particle level using the profile likelihood formalism. Asymmetries are found to be consistent with Monte Carlo predictions within statistically-dominated uncertainties.