Analysis of the Wtb vertex from the measurement of triple-differential angular decay rates of single top quarks produced in the t-channel at √s=8 TeV with the ATLAS detector

The ATLAS Collaboration

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    Abstract

    The electroweak production and subsequent decay of single top quarks in the t-channel is determined by the properties of the Wtb vertex, which can be described by the complex parameters of an effective Lagrangian. An analysis of a triple-differential decay rate in t-channel production is used to simultaneously determine five generalised helicity fractions and phases, as well as the polarisation of the produced top quark. The complex parameters are then constrained. This analysis is based on 20.2 fb−1 of proton-proton collision data at a centre-of-mass energy of 8 TeV collected with the ATLAS detector at the LHC. The fraction of decays containing transversely polarised W bosons is measured to be f1 = 0.30 ± 0.05. The phase between amplitudes for transversely and longitudinally polarised W bosons recoiling against left-handed b-quarks is measured to be δ = 0.002π+ 0.017π + 0.016π, giving no indication of CP violation. The fractions of longitudinal or transverse W bosons accompanied by right-handed b-quarks are also constrained. Based on these measurements, limits are placed at 95% CL on the ratio of the complex coupling parameters Re [gR/VL ∈ [−0.12, 0.17] and Im [gR/VL ∈ [−0.07, 0.06]. Constraints are also placed on the ratios |VR/VL| and |gL/VL|. In addition, the polarisation of single top quarks in the t-channel is constrained to be P > 0.72 (95% CL). None of the above measurements make assumptions about the value of any of the other parameters or couplings and all of them are in agreement with the Standard Model.[Figure not available: see fulltext.].

    Original languageEnglish
    Article number17
    JournalJournal of High Energy Physics
    Volume2017
    Issue number12
    DOIs
    Publication statusPublished - 2017 Dec 1

    Fingerprint

    decay rates
    apexes
    quarks
    detectors
    bosons
    recoilings
    virtual reality
    protons
    decay
    polarization
    CP violation
    center of mass
    indication
    collisions
    energy

    Keywords

    • Electroweak interaction
    • Hadron-Hadron scattering (experiments)
    • Top physics

    ASJC Scopus subject areas

    • Nuclear and High Energy Physics

    Cite this

    @article{560fc26678034656b0b37e902bdf7edb,
    title = "Analysis of the Wtb vertex from the measurement of triple-differential angular decay rates of single top quarks produced in the t-channel at √s=8 TeV with the ATLAS detector",
    abstract = "The electroweak production and subsequent decay of single top quarks in the t-channel is determined by the properties of the Wtb vertex, which can be described by the complex parameters of an effective Lagrangian. An analysis of a triple-differential decay rate in t-channel production is used to simultaneously determine five generalised helicity fractions and phases, as well as the polarisation of the produced top quark. The complex parameters are then constrained. This analysis is based on 20.2 fb−1 of proton-proton collision data at a centre-of-mass energy of 8 TeV collected with the ATLAS detector at the LHC. The fraction of decays containing transversely polarised W bosons is measured to be f1 = 0.30 ± 0.05. The phase between amplitudes for transversely and longitudinally polarised W bosons recoiling against left-handed b-quarks is measured to be δ− = 0.002π+ 0.017π + 0.016π, giving no indication of CP violation. The fractions of longitudinal or transverse W bosons accompanied by right-handed b-quarks are also constrained. Based on these measurements, limits are placed at 95{\%} CL on the ratio of the complex coupling parameters Re [gR/VL ∈ [−0.12, 0.17] and Im [gR/VL ∈ [−0.07, 0.06]. Constraints are also placed on the ratios |VR/VL| and |gL/VL|. In addition, the polarisation of single top quarks in the t-channel is constrained to be P > 0.72 (95{\%} CL). None of the above measurements make assumptions about the value of any of the other parameters or couplings and all of them are in agreement with the Standard Model.[Figure not available: see fulltext.].",
    keywords = "Electroweak interaction, Hadron-Hadron scattering (experiments), Top physics",
    author = "{The ATLAS Collaboration} and M. Aaboud and G. Aad and B. Abbott and J. Abdallah and O. Abdinov and B. Abeloos and Abidi, {S. H.} 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 J. Adelman and M. Adersberger and T. Adye and Affolder, {A. A.} and T. Agatonovic-Jovin and C. Agheorghiesei and Aguilar-Saavedra, {J. A.} and Ahlen, {S. P.} and F. Ahmadov and G. Aielli and S. Akatsuka and H. Akerstedt and {\AA}kesson, {T. P.A.} and E. Akilli and Akimov, {A. V.} and Alberghi, {G. L.} and J. Albert and P. Albicocco 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 Takashi Mitani and Masahiro Morinaga and Kohei Yorita",
    year = "2017",
    month = "12",
    day = "1",
    doi = "10.1007/JHEP12(2017)017",
    language = "English",
    volume = "2017",
    journal = "Journal of High Energy Physics",
    issn = "1126-6708",
    publisher = "Springer Verlag",
    number = "12",

    }

    TY - JOUR

    T1 - Analysis of the Wtb vertex from the measurement of triple-differential angular decay rates of single top quarks produced in the t-channel at √s=8 TeV with the ATLAS detector

    AU - The ATLAS Collaboration

    AU - Aaboud, M.

    AU - Aad, G.

    AU - Abbott, B.

    AU - Abdallah, J.

    AU - Abdinov, O.

    AU - Abeloos, B.

    AU - Abidi, S. H.

    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 - Adelman, J.

    AU - Adersberger, M.

    AU - Adye, T.

    AU - Affolder, A. A.

    AU - Agatonovic-Jovin, T.

    AU - Agheorghiesei, C.

    AU - Aguilar-Saavedra, J. A.

    AU - Ahlen, S. P.

    AU - Ahmadov, F.

    AU - Aielli, G.

    AU - Akatsuka, S.

    AU - Akerstedt, H.

    AU - Åkesson, T. P.A.

    AU - Akilli, E.

    AU - Akimov, A. V.

    AU - Alberghi, G. L.

    AU - Albert, J.

    AU - Albicocco, P.

    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 - Mitani, Takashi

    AU - Morinaga, Masahiro

    AU - Yorita, Kohei

    PY - 2017/12/1

    Y1 - 2017/12/1

    N2 - The electroweak production and subsequent decay of single top quarks in the t-channel is determined by the properties of the Wtb vertex, which can be described by the complex parameters of an effective Lagrangian. An analysis of a triple-differential decay rate in t-channel production is used to simultaneously determine five generalised helicity fractions and phases, as well as the polarisation of the produced top quark. The complex parameters are then constrained. This analysis is based on 20.2 fb−1 of proton-proton collision data at a centre-of-mass energy of 8 TeV collected with the ATLAS detector at the LHC. The fraction of decays containing transversely polarised W bosons is measured to be f1 = 0.30 ± 0.05. The phase between amplitudes for transversely and longitudinally polarised W bosons recoiling against left-handed b-quarks is measured to be δ− = 0.002π+ 0.017π + 0.016π, giving no indication of CP violation. The fractions of longitudinal or transverse W bosons accompanied by right-handed b-quarks are also constrained. Based on these measurements, limits are placed at 95% CL on the ratio of the complex coupling parameters Re [gR/VL ∈ [−0.12, 0.17] and Im [gR/VL ∈ [−0.07, 0.06]. Constraints are also placed on the ratios |VR/VL| and |gL/VL|. In addition, the polarisation of single top quarks in the t-channel is constrained to be P > 0.72 (95% CL). None of the above measurements make assumptions about the value of any of the other parameters or couplings and all of them are in agreement with the Standard Model.[Figure not available: see fulltext.].

    AB - The electroweak production and subsequent decay of single top quarks in the t-channel is determined by the properties of the Wtb vertex, which can be described by the complex parameters of an effective Lagrangian. An analysis of a triple-differential decay rate in t-channel production is used to simultaneously determine five generalised helicity fractions and phases, as well as the polarisation of the produced top quark. The complex parameters are then constrained. This analysis is based on 20.2 fb−1 of proton-proton collision data at a centre-of-mass energy of 8 TeV collected with the ATLAS detector at the LHC. The fraction of decays containing transversely polarised W bosons is measured to be f1 = 0.30 ± 0.05. The phase between amplitudes for transversely and longitudinally polarised W bosons recoiling against left-handed b-quarks is measured to be δ− = 0.002π+ 0.017π + 0.016π, giving no indication of CP violation. The fractions of longitudinal or transverse W bosons accompanied by right-handed b-quarks are also constrained. Based on these measurements, limits are placed at 95% CL on the ratio of the complex coupling parameters Re [gR/VL ∈ [−0.12, 0.17] and Im [gR/VL ∈ [−0.07, 0.06]. Constraints are also placed on the ratios |VR/VL| and |gL/VL|. In addition, the polarisation of single top quarks in the t-channel is constrained to be P > 0.72 (95% CL). None of the above measurements make assumptions about the value of any of the other parameters or couplings and all of them are in agreement with the Standard Model.[Figure not available: see fulltext.].

    KW - Electroweak interaction

    KW - Hadron-Hadron scattering (experiments)

    KW - Top physics

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    U2 - 10.1007/JHEP12(2017)017

    DO - 10.1007/JHEP12(2017)017

    M3 - Article

    AN - SCOPUS:85037716065

    VL - 2017

    JO - Journal of High Energy Physics

    JF - Journal of High Energy Physics

    SN - 1126-6708

    IS - 12

    M1 - 17

    ER -