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

Summary, in English

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.

• Author: 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 Viazlo
• Department/s: Particle and nuclear physics; eSSENCE: The e-Science Collaboration
• Publishing year: 2018
• Language: English
• Publication/Series: European Physical Journal C
• Volume: 78
• Issue: 2
• Links: http://dx.doi.org/10.1140/epjc/s10052-018-5619-1
• Document type: Journal article
• Publisher: Springer
• Topic: Subatomic Physics
• Status: Published
• ISBN/ISSN/Other: ISSN: 1434-6044