Search for flavour-changing neutral current top quark decays t → Hq in pp collisions at √s=8 TeV with the ATLAS detector

The ATLAS collaboration

    Research output: Contribution to journalArticle

    Abstract

    Abstract: A search for flavour-changing neutral current decays of a top quark to an uptype quark (q = u, c) and the Standard Model Higgs boson, where the Higgs boson decays to(Formula Presented.), is presented. The analysis searches for top quark pair events in which one top quark decays to Wb, with the W boson decaying leptonically, and the other top quark decays to Hq. The search is based on pp collisions at (Formula Presented.) TeV recorded in 2012 with the ATLAS detector at the CERN Large Hadron Collider and uses an integrated luminosity of 20.3 fb−1. Data are analysed in the lepton-plus-jets final state, characterised by an isolated electron or muon and at least four jets. The search exploits the high multiplicity of b-quark jets characteristic of signal events, and employs a likelihood discriminant that uses the kinematic differences between the signal and the background, which is dominated by (Formula Presented.) decays. No significant excess of events above the background expectation is found, and observed (expected) 95% CL upper limits of 0.56% (0.42%) and 0.61% (0.64%) are derived for the t → Hc and t → Hu branching ratios respectively. The combination of this search with other ATLAS searches in the H → γγ and H → WW*, ττ decay modes significantly improves the sensitivity, yielding observed (expected) 95% CL upper limits on the t → Hc and t → Hu branching ratios of 0.46% (0.25%) and 0.45% (0.29%) respectively. The corresponding combined observed (expected) upper limits on the |λtcH| and |λtuH| couplings are 0.13 (0.10) and 0.13 (0.10) respectively. These are the most restrictive direct bounds on tqH interactions measured so far.[Figure not available: see fulltext.]

    Original languageEnglish (US)
    Article number61
    Pages (from-to)1-65
    Number of pages65
    JournalJournal of High Energy Physics
    Volume2015
    Issue number12
    DOIs
    StatePublished - Dec 1 2015

    Fingerprint

    neutral currents
    quarks
    collisions
    detectors
    decay
    Higgs bosons
    leptons
    muons
    kinematics
    bosons
    luminosity
    sensitivity
    electrons
    interactions

    Keywords

    • FCNC Interactions
    • Hadron-Hadron Scattering
    • Higgs Physics
    • Top Physics

    ASJC Scopus subject areas

    • Nuclear and High Energy Physics

    Cite this

    Search for flavour-changing neutral current top quark decays t → Hq in pp collisions at √s=8 TeV with the ATLAS detector. / The ATLAS collaboration.

    In: Journal of High Energy Physics, Vol. 2015, No. 12, 61, 01.12.2015, p. 1-65.

    Research output: Contribution to journalArticle

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    title = "Search for flavour-changing neutral current top quark decays t → Hq in pp collisions at √s=8 TeV with the ATLAS detector",
    abstract = "Abstract: A search for flavour-changing neutral current decays of a top quark to an uptype quark (q = u, c) and the Standard Model Higgs boson, where the Higgs boson decays to(Formula Presented.), is presented. The analysis searches for top quark pair events in which one top quark decays to Wb, with the W boson decaying leptonically, and the other top quark decays to Hq. The search is based on pp collisions at (Formula Presented.) TeV recorded in 2012 with the ATLAS detector at the CERN Large Hadron Collider and uses an integrated luminosity of 20.3 fb−1. Data are analysed in the lepton-plus-jets final state, characterised by an isolated electron or muon and at least four jets. The search exploits the high multiplicity of b-quark jets characteristic of signal events, and employs a likelihood discriminant that uses the kinematic differences between the signal and the background, which is dominated by (Formula Presented.) decays. No significant excess of events above the background expectation is found, and observed (expected) 95{\%} CL upper limits of 0.56{\%} (0.42{\%}) and 0.61{\%} (0.64{\%}) are derived for the t → Hc and t → Hu branching ratios respectively. The combination of this search with other ATLAS searches in the H → γγ and H → WW*, ττ decay modes significantly improves the sensitivity, yielding observed (expected) 95{\%} CL upper limits on the t → Hc and t → Hu branching ratios of 0.46{\%} (0.25{\%}) and 0.45{\%} (0.29{\%}) respectively. The corresponding combined observed (expected) upper limits on the |λtcH| and |λtuH| couplings are 0.13 (0.10) and 0.13 (0.10) respectively. These are the most restrictive direct bounds on tqH interactions measured so far.[Figure not available: see fulltext.]",
    keywords = "FCNC Interactions, Hadron-Hadron Scattering, Higgs Physics, Top Physics",
    author = "{The ATLAS collaboration}, {ATLAS collaboration} and G. Aad and B. Abbott and J. Abdallah and O. Abdinov and R. Aben and M. Abolins and AbouZeid, {O. S.} and H. Abramowicz and H. Abreu and R. Abreu and Y. Abulaiti and Acharya, {B. S.} 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 J. Agricola 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 G. Alimonti and L. Alio and J. Alison and Alkire, {S. P.} and Allbrooke, {B. M M} and Allport, {P. P.} and A. Aloisio and A. Alonso and F. Alonso and K. Cranmer and A. Haas and Mincer, {A. I.} and P. Nemethy",
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    T1 - Search for flavour-changing neutral current top quark decays t → Hq in pp collisions at √s=8 TeV with the ATLAS detector

    AU - The ATLAS collaboration

    AU - Aad, G.

    AU - Abbott, B.

    AU - Abdallah, J.

    AU - Abdinov, O.

    AU - Aben, R.

    AU - Abolins, M.

    AU - AbouZeid, O. S.

    AU - Abramowicz, H.

    AU - Abreu, H.

    AU - Abreu, R.

    AU - Abulaiti, Y.

    AU - Acharya, B. 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 - Agricola, J.

    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 - Alimonti, G.

    AU - Alio, L.

    AU - Alison, J.

    AU - Alkire, S. P.

    AU - Allbrooke, B. M M

    AU - Allport, P. P.

    AU - Aloisio, A.

    AU - Alonso, A.

    AU - Alonso, F.

    AU - Cranmer, K.

    AU - Haas, A.

    AU - Mincer, A. I.

    AU - Nemethy, P.

    PY - 2015/12/1

    Y1 - 2015/12/1

    N2 - Abstract: A search for flavour-changing neutral current decays of a top quark to an uptype quark (q = u, c) and the Standard Model Higgs boson, where the Higgs boson decays to(Formula Presented.), is presented. The analysis searches for top quark pair events in which one top quark decays to Wb, with the W boson decaying leptonically, and the other top quark decays to Hq. The search is based on pp collisions at (Formula Presented.) TeV recorded in 2012 with the ATLAS detector at the CERN Large Hadron Collider and uses an integrated luminosity of 20.3 fb−1. Data are analysed in the lepton-plus-jets final state, characterised by an isolated electron or muon and at least four jets. The search exploits the high multiplicity of b-quark jets characteristic of signal events, and employs a likelihood discriminant that uses the kinematic differences between the signal and the background, which is dominated by (Formula Presented.) decays. No significant excess of events above the background expectation is found, and observed (expected) 95% CL upper limits of 0.56% (0.42%) and 0.61% (0.64%) are derived for the t → Hc and t → Hu branching ratios respectively. The combination of this search with other ATLAS searches in the H → γγ and H → WW*, ττ decay modes significantly improves the sensitivity, yielding observed (expected) 95% CL upper limits on the t → Hc and t → Hu branching ratios of 0.46% (0.25%) and 0.45% (0.29%) respectively. The corresponding combined observed (expected) upper limits on the |λtcH| and |λtuH| couplings are 0.13 (0.10) and 0.13 (0.10) respectively. These are the most restrictive direct bounds on tqH interactions measured so far.[Figure not available: see fulltext.]

    AB - Abstract: A search for flavour-changing neutral current decays of a top quark to an uptype quark (q = u, c) and the Standard Model Higgs boson, where the Higgs boson decays to(Formula Presented.), is presented. The analysis searches for top quark pair events in which one top quark decays to Wb, with the W boson decaying leptonically, and the other top quark decays to Hq. The search is based on pp collisions at (Formula Presented.) TeV recorded in 2012 with the ATLAS detector at the CERN Large Hadron Collider and uses an integrated luminosity of 20.3 fb−1. Data are analysed in the lepton-plus-jets final state, characterised by an isolated electron or muon and at least four jets. The search exploits the high multiplicity of b-quark jets characteristic of signal events, and employs a likelihood discriminant that uses the kinematic differences between the signal and the background, which is dominated by (Formula Presented.) decays. No significant excess of events above the background expectation is found, and observed (expected) 95% CL upper limits of 0.56% (0.42%) and 0.61% (0.64%) are derived for the t → Hc and t → Hu branching ratios respectively. The combination of this search with other ATLAS searches in the H → γγ and H → WW*, ττ decay modes significantly improves the sensitivity, yielding observed (expected) 95% CL upper limits on the t → Hc and t → Hu branching ratios of 0.46% (0.25%) and 0.45% (0.29%) respectively. The corresponding combined observed (expected) upper limits on the |λtcH| and |λtuH| couplings are 0.13 (0.10) and 0.13 (0.10) respectively. These are the most restrictive direct bounds on tqH interactions measured so far.[Figure not available: see fulltext.]

    KW - FCNC Interactions

    KW - Hadron-Hadron Scattering

    KW - Higgs Physics

    KW - Top Physics

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    EP - 65

    JO - Journal of High Energy Physics

    JF - Journal of High Energy Physics

    SN - 1126-6708

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