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Scientific article
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English

Measurement of the polarisation of W bosons produced in top-quark decays using dilepton events at s=13 TeV with the ATLAS experiment

ContributorsATLAS Collaboration
Published inPhysics letters. B, vol. 843, 137829
Publication date2023
First online date2023-06-05
Abstract

A measurement of the polarisation of W bosons produced in top-quark decays is presented, using proton–proton collision data at a centre-of-mass energy of s=13 TeV. The data were collected by the ATLAS detector at the Large Hadron Collider and correspond to an integrated luminosity of 139 fb−1. The measurement is performed selecting tt¯ events decaying into final states with two charged leptons (electrons or muons) and at least two b-tagged jets. The polarisation is extracted from the differential cross-section distribution of the cos⁡θ⁎ variable, where θ⁎ is the angle between the momentum direction of the charged lepton from the W boson decay and the reversed momentum direction of the b-quark from the top-quark decay, both calculated in the W boson rest frame. Parton-level results, corrected for the detector acceptance and resolution, are presented for the cos⁡θ⁎ angle. The measured fractions of longitudinal, left- and right-handed polarisation states are found to be f0=0.684±0.005(stat.)±0.014(syst.), fL=0.318±0.003(stat.)±0.008(syst.) and fR=−0.002±0.002(stat.)±0.014(syst.), in agreement with the Standard Model prediction.

eng
Keywords
  • P p: colliding beams
  • Top: leptonic decay
  • Top: pair production
  • W: leptonic decay
  • P p: scattering
  • W: polarization
  • Final state: ((n)jet dilepton)
  • ATLAS
  • Muon
  • Polarization: longitudinal
  • Resolution
  • Acceptance
  • Electron
  • W: left-handed
  • W: right-handed
  • CERN LHC Coll
  • Differential cross section: measured
  • Angular dependence
  • Experimental results
  • 13000 GeV-cms
Citation (ISO format)
ATLAS Collaboration. Measurement of the polarisation of W bosons produced in top-quark decays using dilepton events at s=13 TeV with the ATLAS experiment. In: Physics letters. B, 2023, vol. 843, p. 137829. doi: 10.1016/j.physletb.2023.137829
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ISSN of the journal0370-2693
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