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Measurement of t polarisation in Z/?* ? tt decays in proton–proton collisions at vs = 8 TeV with the ATLAS detector

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posted on 2023-06-09, 13:29 authored by Benedict AllbrookeBenedict Allbrooke, Lily AsquithLily Asquith, Alessandro CerriAlessandro Cerri, C A Chavez Barajas, Antonella De SantoAntonella De Santo, Fabrizio SalvatoreFabrizio Salvatore, I Santoyo Castillo, K Suruliz, Mark SuttonMark Sutton, Iacopo Vivarelli, The ATLAS Collaboration
This paper presents a measurement of the polarisation of t leptons produced in Z/? * ? tt decays which is performed with a dataset of proton—proton collisions at vs = 8 TeV, corresponding to an integrated luminosity of 20.2 fb-1 recorded with the ATLAS detector at the LHC in 2012. The Z/?* ? tt decays are reconstructed from a hadronically decaying t lepton with a single charged particle in the final state, accompanied by a t lepton that decays leptonically. The t polarisation is inferred from the relative fraction of energy carried by charged and neutral hadrons in the hadronic t decays. The polarisation is measured in a fiducial region that corresponds to the kinematic region accessible to this analysis. The t polarisation extracted over the full phase space within the Z/?* mass range of 66 < mZ/?* < 116GeV is found to be Pt = -0.14±0.02(stat)±0.04(syst). It is in agreement with the Standard Model prediction of Pt = -0.1517 ± 0.0019, which is obtained from the ALPGEN event generator interfaced with the PYTHIA 6 parton shower modelling and the TAUOLA t decay library.

Funding

ATLAS; G0275; STFC-SCIENCE AND TECHNOLOGY FACILITIES COUNCIL; ST/I006048/1

History

Publication status

  • Published

File Version

  • Published version

Journal

European Physical Journal C: Particles and Fields

ISSN

1434-6044

Publisher

Springer Verlag

Issue

163

Volume

78

Department affiliated with

  • Physics and Astronomy Publications

Research groups affiliated with

  • Experimental Particle Physics Research Group Publications

Full text available

  • Yes

Peer reviewed?

  • Yes

Legacy Posted Date

2018-05-25

First Open Access (FOA) Date

2018-05-25

First Compliant Deposit (FCD) Date

2018-05-24

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