Measurement of τ polarization in W→τν decays with the ATLAS detector in pp collisions at $\sqrt{s} =7~\mathrm{TeV}$

Abstract

In this paper, a measurement of <i>τ</i> polarization in <i>W</i>→<i>τν</i> decays is presented. It is measured from the energies of the decay products in hadronic <i>τ</i> decays with a single final state charged particle. The data, corresponding to an integrated luminosity of 24 pb^-1, were collected by the ATLAS experiment at the Large Hadron Collider in 2010. The measured value of the <i>τ</i> polarization is [Formula: see text], in agreement with the Standard Model prediction, and is consistent with a physically allowed 95 % CL interval [-1,-0.91]. Measurements of <i>τ</i> polarization have not previously been made at hadron colliders.