Measurement of τ polarisation in Z/ γ∗→ ττ decays in proton–proton collisions at √s=8 TeV with the ATLAS detector

M Aaboud, G Aad, B. Abbott, O Abdinov, B Abeloos, S. H. Abidi, Torsten Åkesson, Simona Bocchetta, Caterina Doglioni, Vincent Hedberg, Göran Jarlskog, Charles Kalderon, Edgar Kellermann, Else Lytken, Katja Mankinen, Ulf Mjörnmark, Ruth Pöttgen, Trine Poulsen, Oxana Smirnova, Oleksandr ViazloATLAS Collaboration

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Abstract

This paper presents a measurement of the polarisation of τ leptons produced in Z/ γ∗→ ττ decays which is performed with a dataset of proton—proton collisions at s=8 TeV, corresponding to an integrated luminosity of 20.2 fb- 1 recorded with the ATLAS detector at the LHC in 2012. The Z/ γ∗→ ττ decays are reconstructed from a hadronically decaying τ lepton with a single charged particle in the final state, accompanied by a τ lepton that decays leptonically. The τ polarisation is inferred from the relative fraction of energy carried by charged and neutral hadrons in the hadronic τ decays. The polarisation is measured in a fiducial region that corresponds to the kinematic region accessible to this analysis. The τ polarisation extracted over the full phase space within the Z/ γ∗ mass range of 66 <mZ/ 116 GeV is found to be Pτ= - 0.14 ± 0.02 (stat) ± 0.04 (syst). It is in agreement with the Standard Model prediction of Pτ= - 0.1517 ± 0.0019 , which is obtained from the ALPGEN event generator interfaced with the PYTHIA 6 parton shower modelling and the TAUOLA τ decay library. © 2018, CERN for the benefit of the ATLAS collaboration.
Original languageEnglish
Article number163
JournalEuropean Physical Journal C
Volume78
Issue number2
DOIs
Publication statusPublished - 2018

Bibliographical note

Export Date: 8 March 2018

Subject classification (UKÄ)

  • Subatomic Physics

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