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

The ATLAS Collaboration

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    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.

    Original languageEnglish
    Article number264
    JournalEuropean Physical Journal C
    Volume77
    Issue number4
    DOIs
    Publication statusPublished - 2017 Apr 1

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    Bosons
    leptons
    bosons
    Polarization
    collisions
    polarization
    quarks
    decay
    products
    Luminance
    apexes
    luminosity

    ASJC Scopus subject areas

    • Engineering (miscellaneous)
    • Physics and Astronomy (miscellaneous)

    Cite this

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

    In: European Physical Journal C, Vol. 77, No. 4, 264, 01.04.2017.

    Research output: Contribution to journalArticle

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    title = "Measurement of the W boson polarisation in tt¯ events from pp collisions at √s = 8 TeV in the lepton + jets channel with ATLAS",
    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.",
    author = "{The ATLAS Collaboration} and M. Aaboud and G. Aad and B. Abbott and J. Abdallah and O. Abdinov and B. Abeloos and AbouZeid, {O. S.} and Abraham, {N. L.} and H. Abramowicz and H. Abreu and R. Abreu and Y. Abulaiti and Acharya, {B. S.} and S. Adachi and L. Adamczyk and Adams, {D. L.} and J. Adelman and S. Adomeit and T. Adye and Affolder, {A. A.} and T. Agatonovic-Jovin and Aguilar-Saavedra, {J. A.} and Ahlen, {S. P.} and F. Ahmadov and G. Aielli and H. Akerstedt and {\AA}kesson, {T. P.A.} and Akimov, {A. V.} and Alberghi, {G. L.} and J. Albert and S. Albrand and {Alconada Verzini}, {M. J.} and M. Aleksa and Aleksandrov, {I. N.} and C. Alexa and G. Alexander and T. Alexopoulos and M. Alhroob and B. Ali and M. Aliev and G. Alimonti and J. Alison and Alkire, {S. P.} and Allbrooke, {B. M.M.} and Allen, {B. W.} and Allport, {P. P.} and A. Aloisio and T. Iizawa and Masahiro Morinaga and Kohei Yorita",
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    T1 - Measurement of the W boson polarisation in tt¯ events from pp collisions at √s = 8 TeV in the lepton + jets channel with ATLAS

    AU - The ATLAS Collaboration

    AU - Aaboud, M.

    AU - Aad, G.

    AU - Abbott, B.

    AU - Abdallah, J.

    AU - Abdinov, O.

    AU - Abeloos, B.

    AU - AbouZeid, O. S.

    AU - Abraham, N. L.

    AU - Abramowicz, H.

    AU - Abreu, H.

    AU - Abreu, R.

    AU - Abulaiti, Y.

    AU - Acharya, B. S.

    AU - Adachi, S.

    AU - Adamczyk, L.

    AU - Adams, D. L.

    AU - Adelman, J.

    AU - Adomeit, S.

    AU - Adye, T.

    AU - Affolder, A. A.

    AU - Agatonovic-Jovin, T.

    AU - Aguilar-Saavedra, J. A.

    AU - Ahlen, S. P.

    AU - Ahmadov, F.

    AU - Aielli, G.

    AU - Akerstedt, H.

    AU - Åkesson, T. P.A.

    AU - Akimov, A. V.

    AU - Alberghi, G. L.

    AU - Albert, J.

    AU - Albrand, S.

    AU - Alconada Verzini, M. J.

    AU - Aleksa, M.

    AU - Aleksandrov, I. N.

    AU - Alexa, C.

    AU - Alexander, G.

    AU - Alexopoulos, T.

    AU - Alhroob, M.

    AU - Ali, B.

    AU - Aliev, M.

    AU - Alimonti, G.

    AU - Alison, J.

    AU - Alkire, S. P.

    AU - Allbrooke, B. M.M.

    AU - Allen, B. W.

    AU - Allport, P. P.

    AU - Aloisio, A.

    AU - Iizawa, T.

    AU - Morinaga, Masahiro

    AU - Yorita, Kohei

    PY - 2017/4/1

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    N2 - 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.

    AB - 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.

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    U2 - 10.1140/epjc/s10052-017-4819-4

    DO - 10.1140/epjc/s10052-017-4819-4

    M3 - Article

    VL - 77

    JO - European Physical Journal C

    JF - European Physical Journal C

    SN - 1434-6044

    IS - 4

    M1 - 264

    ER -