  Various differential cross-sections are measured in top-quark pair
($t\bar{t}$) events produced in proton-proton collisions at a centre-of-mass
energy of $\sqrt{s} = 7$ TeV at the LHC with the ATLAS detector. These
differential cross-sections are presented in a data set corresponding to an
integrated luminosity of $4.6$ fb$^{-1}$. The differential cross-sections are
presented in terms of kinematic variables, such as momentum, rapidity and
invariant mass, of a top-quark proxyreferred to as the pseudo-top-quark as well
as the pseudo-top-quark pair system. The dependence of the measurement on
theoretical models is minimal.
  The measurements are performed on $t\bar{t}$ events in the lepton+jets
channel, requiring exactly one charged lepton and at least four jets with at
least two of them tagged as originating from a $b$-quark. The hadronic and
leptonic pseudo-top-quarks are defined via the leptonic or hadronic decay mode
of the $W$ boson produced by the top-quark decay in events with a single
charged lepton. Differential cross-section measurements of the pseudo-top-quark
variables are compared with several Monte Carlo models that implement
next-to-leading order or leading-order multi-leg matrix-element calculations.
