Measurements of top-quark pair differential cross-sections in the lepton+jets channel in pp collisions at $\sqrt{s}=13$ TeV using the ATLAS detector

Measurements of differential cross-sections of top-quark pair production are presented as a~function of the top-quark and $t\bar{t}$ system kinematic observables in proton--proton collisions at a~centre-of-mass energy of $\sqrt{s}=13\,{\rm TeV}$. The dataset corresponds to an integrated luminosity of $3.2\,{\rm fb}^{-1}$, recorded in 2015 with the ATLAS detector at the CERN Large Hadron Collider. Events with one lepton and jets in the final state are used for the measurement. Two separate selections are applied that each focus on different top-quark momentum phase-spaces, denoted as resolved and boosted topologies of the $t\bar{t}$ final state. The measured spectra are corrected for detector effects and are compared to several Monte Carlo simulations. The results are in fair agreement with the predictions over a wide kinematic range. Nevertheless, most event generators predict a harder top-quark transverse momentum distribution at high values than what is observed in the data.