Measurement of the total and differential cross-sections of $t\bar{t}W$ production in $pp$ collisions at 13 TeV with the ATLAS detector

Measurements of both the inclusive and differential production cross-sections of a top-quark-antiquark pair in association with a $W$ boson ($t\bar{t}W$) are presented. The measurements are performed by targeting final states with two same-sign or three isolated leptons (electrons or muons) and are based on $\sqrt{s}=13$ TeV proton–proton collision data with an integrated luminosity of 140 fb$^{−1}$, recorded from 2015 to 2018 with the ATLAS detector at the Large Hadron Collider. The inclusive 𝑡𝑡 ̄𝑊 production cross-section is measuredto be $890\pm80$ fb, compared to the reference theoretical prediction of $722^{+70}_{-78}$ (scale) $\pm7$ (PDF) fb. Differential cross-section measurements characterise this process in detail for the first time. Several particle-level observables are compared to a variety of theoretical predictions which are generally in good agreement with the normalised differential cross-section results