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Measurement of the W boson polarisation in tt¯ events from pp collisions at √s = 8 TeV in the lepton + jets channel with ATLAS

Aaboud, M; Aad, G.; Abbott, B; Abdallah, J.; Abdinov, O; Abeloos, B; Åkesson, Torsten LU ; Bocchetta, Simona LU ; BRYNGEMARK, LENE LU and Doglioni, Caterina LU , et al. (2017) In European Physical Journal C 77(4).
Abstract
This paper presents a measurement of the polarisation of W bosons from tt¯ decays, reconstructed in events with one high-pT lepton and at least four jets. Data from pp collisions at the LHC were collected at s = 8 TeV and correspond to an integrated luminosity of 20.2 fb- 1. The angle θ∗ between the b-quark from the top quark decay and a direct W boson decay product in the W boson rest frame is sensitive to the W boson polarisation. Two different W decay products are used as polarisation analysers: the charged lepton and the down-type quark for the leptonically and hadronically decaying W boson, respectively. The most precise measurement of the W boson polarisation via the distribution of cos θ∗ is obtained using the leptonic analyser and... (More)
This paper presents a measurement of the polarisation of W bosons from tt¯ decays, reconstructed in events with one high-pT lepton and at least four jets. Data from pp collisions at the LHC were collected at s = 8 TeV and correspond to an integrated luminosity of 20.2 fb- 1. The angle θ∗ between the b-quark from the top quark decay and a direct W boson decay product in the W boson rest frame is sensitive to the W boson polarisation. Two different W decay products are used as polarisation analysers: the charged lepton and the down-type quark for the leptonically and hadronically decaying W boson, respectively. The most precise measurement of the W boson polarisation via the distribution of cos θ∗ is obtained using the leptonic analyser and events in which at least two of the jets are tagged as b-quark jets. The fitted fractions of longitudinal, left- and right-handed polarisation states are F0=0.709±0.019, FL=0.299±0.015 and FR=-0.008±0.014, and are the most precisely measured W boson polarisation fractions to date. Limits on anomalous couplings of the Wtb vertex are set. © 2017, CERN for the benefit of the ATLAS collaboration. (Less)
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European Physical Journal C
volume
77
issue
4
publisher
Springer
external identifiers
  • scopus:85018254033
ISSN
1434-6044
DOI
10.1140/epjc/s10052-017-4819-4
language
English
LU publication?
yes
id
0dde6cc8-f6ea-4180-a994-2e1f7c416153
date added to LUP
2017-06-12 10:48:28
date last changed
2018-01-07 12:07:06
@article{0dde6cc8-f6ea-4180-a994-2e1f7c416153,
  abstract     = {This paper presents a measurement of the polarisation of W bosons from tt¯ decays, reconstructed in events with one high-pT lepton and at least four jets. Data from pp collisions at the LHC were collected at s = 8 TeV and correspond to an integrated luminosity of 20.2 fb- 1. The angle θ∗ between the b-quark from the top quark decay and a direct W boson decay product in the W boson rest frame is sensitive to the W boson polarisation. Two different W decay products are used as polarisation analysers: the charged lepton and the down-type quark for the leptonically and hadronically decaying W boson, respectively. The most precise measurement of the W boson polarisation via the distribution of cos θ∗ is obtained using the leptonic analyser and events in which at least two of the jets are tagged as b-quark jets. The fitted fractions of longitudinal, left- and right-handed polarisation states are F0=0.709±0.019, FL=0.299±0.015 and FR=-0.008±0.014, and are the most precisely measured W boson polarisation fractions to date. Limits on anomalous couplings of the Wtb vertex are set. © 2017, CERN for the benefit of the ATLAS collaboration.},
  articleno    = {264},
  author       = {Aaboud, M and Aad, G. and Abbott, B and Abdallah, J. and Abdinov, O and Abeloos, B and Åkesson, Torsten and Bocchetta, Simona and BRYNGEMARK, LENE and Doglioni, Caterina and Hedberg, Vincent and Jarlskog, Göran and Lytken, Else and Mjörnmark, Ulf and Smirnova, Oxana and Viazlo, Oleksandr and , },
  issn         = {1434-6044},
  language     = {eng},
  number       = {4},
  publisher    = {Springer},
  series       = {European Physical Journal C},
  title        = {Measurement of the W boson polarisation in tt¯ events from pp collisions at √s = 8 TeV in the lepton + jets channel with ATLAS},
  url          = {http://dx.doi.org/10.1140/epjc/s10052-017-4819-4},
  volume       = {77},
  year         = {2017},
}