Measurement of the top polarization in the dilepton final state

A measurement of the top quark polarization in \ttll\ events is performed in a data sample corresponding to a total integrated luminosity of \Lumiyt\ collected by the CMS experiment in pp collisions at a centre-of-mass energy of 7~TeV at the LHC. %In view of a significant excess reported in the top forward backward asymmetry at the Tevatron, The measured value in the helicity basis is $P_{n} = -0.009 \pm 0.029 \pm 0.041$, in agreement with the standard model expectation. %These results are used to constrain contribution from axigluon production as well as from a t-channel \cPWpr\ exchange.