Measurement of $\tau$ Polarization in Wtaunu Decays with the ATLAS Detector in $pp$ Collisions at sqrt{s}~=~7 TeV

In this proceedings, the first measurement of tau polarization at a hadron collider is discussed. The presented method for extracting the tau polarization is independent of the mode of tau production and can be applied to the characterization of new phenomena at the Large Hadron Collider. The method has been applied to Wtaunu decays and the measured value of Ptau = -1.06 +/- 0.04(stat)^{+0.05}_{-0.07} (syst) is in agreement with the Standard Model prediction.