Spin measurement in top quark events at the LHC

Measurements of polarisation and spin correlations are presented in events with top quarks produced in $\mathrm{pp}$ collisions at the LHC. The data correspond to integrated luminosities of $5\:\mathrm{fb^{-1}}$ at $\sqrt{s}=7\:\mathrm{TeV}$ and $20\:\mathrm{fb^{-1}}$ at $\sqrt{s}=8\:\mathrm{TeV}$ collected with the ATLAS and CMS detectors. The top quark polarisation is measured in both single top quark production in the $t$-channel and $\mathrm{t\bar{t}}$ pair-production, from the angular distributions of charged leptons in the rest frame of their parent top quark. The spin correlations are measured in $\mathrm{t\bar{t}}$ events using various angular distributions of the decay products. The measurements are made using both template fitting methods and by unfolding the distributions to the parton-level, where differential measurements with respect to the invariant mass, rapidity, and transverse momentum of the $\mathrm{t\bar{t}}$ system are also made. The spin correlation measurements are used to search for new physics in the form of a light top squark or an anomalous top quark chromo-magnetic dipole moment. All measurements are found to be in agreement with predictions of the standard model.