Top Pair Spin Correlation Studies in CMS

Measurement of $t\bar t$ spin correlations are presented in event with top quarks produced in pp collisions at the LHC. The data correspond to an integrated luminosity of 19.5~fb$^{-1}$ at $\sqrt s$ = 8 TeV and 36~fb$^{-1}$ at $\sqrt s$ = 13 TeV collected at CMS detector. The spin correlations are measured using angular distributions of the leptons in $t\bar t$ events via the dileptonic channel. The spin correlations are probed in two ways. The direct measurement is performed by exploiting the distributions in individual top quark rest frames. The indirect one is performed by constructing the distributions in the laboratory frame. Differential distributions provide both a test of the standard model of particle physics and a measure for the deviations from the standard model that could help to understand the possible signs of new physics.