Measurement of spin correlations in tt production using the matrix element method in the muon+jets final state in pp collisions at √s=8 TeV

The consistency of the spin correlation strength in top quark pair production with the standard model (SM) prediction is tested in the muon+jets final state. The events are selected from pp collisions, collected by the CMS detector, at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.7 fb(-1). The data are compared with the expectation for the spin correlation predicted by the SM and with the expectation of no correlation. Using a template fit method, the fraction of events that show SM spin correlations is measured to be 0.72 0.08 (stat)(-013)(+015) (syst), representing the most precise measurement of this quantity in the muon+jets final state to date.