Hamburg 2016 – scientific programme

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T: Fachverband Teilchenphysik

T 58: Elektroschwache Wechselwirkung (Experiment) I

T 58.1: Talk

Tuesday, March 1, 2016, 16:45–17:00, VMP8 SR 206

Measurement of Tau Polarization in Z Boson Decays at ATLAS — •Benedict Winter, William Davey, and Jochen Dingfelder — Physikalisches Institut, Universität Bonn

Decays of the Z boson in the Standard Model violate parity, leading to a net polarization of the decay products. Z boson decays to pairs of tau leptons provide a unique opportunity to measure the tau polarization by using the kinematics of the subsequent tau decays, hence testing the Standard Model predictions. They also provide a unique opportunity to pioneer experimental techniques that assess the tau helicity and may be used in searches for new particles and to study the properties of the Higgs boson.

In this talk the status of the first measurement of the tau polarization in Z→ττ decays at a hadronic collider is presented. The analysis is based on the 20.3 fb⁻¹ collected by the ATLAS experiment at a center-of-mass energy of √s = 8 TeV. The tau polarization is measured in events in which one tau decays leptonically and the other decays hadronically by using the kinematics of the hadronic decay. A main focus is set on the determination of the systematic uncertainties and the limit setting procedure.