Perspectives for a measurement of the τ polarization in Z → ττ decays with the CMS experiment

The potential of the CMS detector to measure the τ - lepton polarization asymmetry in Z0 decays is studied. Using data corresponding to an integrated luminosity of 19.6 fb−1 at 8 TeV and 2.3 fb−1 at 13 TeV the τ polarization asymmetry is measured exploiting decay channels τ→ρν and τ→a1ν.