Measurement of colour flow in ttbar events with the ATLAS detector

% Previous phenomenological studies and measurements have shown that weighted angular momenta derived from jet constituents encode the colour connections between initiating partons which seed the jets. This article presents measurements of two such distributions, the jet-pull angle and jet-pull magnitude, both of which are derived from the jet-pull angular moment. The measurement is performed in $t\bar{t}$ events with one leptonically decaying $W$~boson and one hadronically decaying $W$~boson using $36.1\,\text{fb}^{-1}$ of $pp$ collision data recorded by the ATLAS detector at $\sqrt{s} = 13 \, \text{TeV}$ delivered by the Large Hadron Collider. The observables are measured for two jet pairings, corresponding to the colour-connected daughters of the $W$~boson and the $b$-jets from the top quark decay. To allow the comparison of the measured distributions to colour model predictions, they are unfolded to particle-level, thereby removing smearing and distortions introduced by the detector. Colour flow according to the Standard Model is preferred by the data. % Tension between % different Monte Carlo predictions is observed. The measured results provide a % valuable input to future Monte Carlo tuning and development.