Measurement of tau polarization in W->taunu decays with the ATLAS detector in pp collisions at sqrt(s) = 7 TeV

TL;DR

This paper reports the first measurement of tau lepton polarization in W boson decays at a hadron collider, using ATLAS data at 7 TeV, confirming Standard Model predictions with high precision.

Contribution

It introduces a novel measurement of tau polarization in W decays at a hadron collider, providing new experimental data in this area.

Findings

Tau polarization measured as Ptau = -1.06 +/- 0.04 (stat) + 0.05/-0.07 (syst)

Results are consistent with Standard Model predictions

First such measurement at a hadron collider

Abstract

In this paper, a measurement of tau polarization in W->taunu decays is presented. It is measured from the energies of the decay products in hadronic tau 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 tau polarization is Ptau = -1.06 +/- 0.04 (stat) + 0.05 (syst) - 0.07 (syst), in agreement with the Standard Model prediction, and is consistent with a physically allowed 95% CL interval [-1,-0.91]. Measurements of tau polarization have not previously been made at hadron colliders.