Measurement of the tt production cross-section using eµ events with b-tagged jets in pp collisions at √s = 7 and 8 TeV with the ATLAS detector

The ATLAS Collaboration

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    Abstract

    The inclusive top quark pair (tt) production cross-section σtt has been measured in proton–proton collisions at √s = 7 TeV and√s = 8 TeV with the ATLAS experiment at the LHC, using tt events with an opposite-charge eμ pair in the final state. The measurement was performed with the 2011 7 TeV dataset corresponding to an integrated luminosity of 4.6 fb−1 and the 2012 8 TeV dataset of 20.3 fb−1. The numbers of events with exactly one and exactly two b-tagged jets were counted and used to simultaneously determine σtt and the efficiency to reconstruct and b-tag a jet from a top quark decay, thereby minimising the associated systematic uncertainties. The cross-section was measured to be: σtt = 182.9 ± 3.1 ± 4.2 ± 3.6 ± 3.3 pb (√s = 7 TeV) and σtt = 242.4 ± 1.7 ± 5.5 ± 7.5 ± 4.2 pb (√s = 8 TeV), where the four uncertainties arise from data statistics, experimental and theoretical systematic effects, knowledge of the integrated luminosity and of the LHC beam energy. The results are consistent with recent theoretical QCD calculations at next-to-next-to-leading order. Fiducial measurements corresponding to the experimental acceptance of the leptons are also reported, together with the ratio of cross-sections measured at the two centre-of-mass energies. The inclusive cross-section results were used to determine the top quark pole mass via the dependence of the theoretically predicted cross-section on mpole t giving a result of mpole t = 172.9+2.5 −2.6 GeV. By looking for an excess of tt production with respect to the QCD prediction, the results were also used to place limits on the pair-production of supersymmetric top squarks t1 with masses close to the top quark mass, decaying via t1 → t χ0 1 to predominantly right-handed top quarks and a light neutralino χ0 1, the lightest supersymmet-ric particle. Top squarks with masses between the top quark mass and 177 GeV are excluded at the 95 % confidence level.

    Original languageEnglish
    Article number3109
    JournalEuropean Physical Journal C
    Volume74
    Issue number10
    DOIs
    Publication statusPublished - 2014 Oct 21

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    quarks
    Detectors
    collisions
    Luminance
    detectors
    cross sections
    pair production
    Poles
    quantum chromodynamics
    luminosity
    Statistics
    acceptability
    center of mass
    leptons
    confidence
    poles
    Experiments
    statistics
    Uncertainty
    energy

    ASJC Scopus subject areas

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

    Cite this

    Measurement of the tt production cross-section using eµ events with b-tagged jets in pp collisions at √s = 7 and 8 TeV with the ATLAS detector. / The ATLAS Collaboration.

    In: European Physical Journal C, Vol. 74, No. 10, 3109, 21.10.2014.

    Research output: Contribution to journalArticle

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    title = "Measurement of the tt production cross-section using eµ events with b-tagged jets in pp collisions at √s = 7 and 8 TeV with the ATLAS detector",
    abstract = "The inclusive top quark pair (tt) production cross-section σtt has been measured in proton–proton collisions at √s = 7 TeV and√s = 8 TeV with the ATLAS experiment at the LHC, using tt events with an opposite-charge eμ pair in the final state. The measurement was performed with the 2011 7 TeV dataset corresponding to an integrated luminosity of 4.6 fb−1 and the 2012 8 TeV dataset of 20.3 fb−1. The numbers of events with exactly one and exactly two b-tagged jets were counted and used to simultaneously determine σtt and the efficiency to reconstruct and b-tag a jet from a top quark decay, thereby minimising the associated systematic uncertainties. The cross-section was measured to be: σtt = 182.9 ± 3.1 ± 4.2 ± 3.6 ± 3.3 pb (√s = 7 TeV) and σtt = 242.4 ± 1.7 ± 5.5 ± 7.5 ± 4.2 pb (√s = 8 TeV), where the four uncertainties arise from data statistics, experimental and theoretical systematic effects, knowledge of the integrated luminosity and of the LHC beam energy. The results are consistent with recent theoretical QCD calculations at next-to-next-to-leading order. Fiducial measurements corresponding to the experimental acceptance of the leptons are also reported, together with the ratio of cross-sections measured at the two centre-of-mass energies. The inclusive cross-section results were used to determine the top quark pole mass via the dependence of the theoretically predicted cross-section on mpole t giving a result of mpole t = 172.9+2.5 −2.6 GeV. By looking for an excess of tt production with respect to the QCD prediction, the results were also used to place limits on the pair-production of supersymmetric top squarks t1 with masses close to the top quark mass, decaying via t1 → t χ0 1 to predominantly right-handed top quarks and a light neutralino χ0 1, the lightest supersymmet-ric particle. Top squarks with masses between the top quark mass and 177 GeV are excluded at the 95 {\%} confidence level.",
    author = "{The ATLAS Collaboration} and G. Aad and B. Abbott and J. Abdallah and {Abdel Khalek}, S. and O. Abdinov and R. Aben and B. Abi 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 T. Agatonovic-Jovin and Aguilar-Saavedra, {J. A.} and M. Agustoni and Ahlen, {S. P.} and F. Ahmadov and G. Aielli and H. Akerstedt and {\AA}kesson, {T. P A} and G. Akimoto 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 G. Alexandre and T. Alexopoulos and M. Alhroob and G. Alimonti and L. Alio and J. Alison and Allbrooke, {B. M M} and Allison, {L. J.} and Allport, {P. P.} and J. Almond and A. Aloisio and Takashi Mitani and Kohei Yorita",
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    T1 - Measurement of the tt production cross-section using eµ events with b-tagged jets in pp collisions at √s = 7 and 8 TeV with the ATLAS detector

    AU - The ATLAS Collaboration

    AU - Aad, G.

    AU - Abbott, B.

    AU - Abdallah, J.

    AU - Abdel Khalek, S.

    AU - Abdinov, O.

    AU - Aben, R.

    AU - Abi, B.

    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 - Agatonovic-Jovin, T.

    AU - Aguilar-Saavedra, J. A.

    AU - Agustoni, M.

    AU - Ahlen, S. P.

    AU - Ahmadov, F.

    AU - Aielli, G.

    AU - Akerstedt, H.

    AU - Åkesson, T. P A

    AU - Akimoto, G.

    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 - Alexandre, G.

    AU - Alexopoulos, T.

    AU - Alhroob, M.

    AU - Alimonti, G.

    AU - Alio, L.

    AU - Alison, J.

    AU - Allbrooke, B. M M

    AU - Allison, L. J.

    AU - Allport, P. P.

    AU - Almond, J.

    AU - Aloisio, A.

    AU - Mitani, Takashi

    AU - Yorita, Kohei

    PY - 2014/10/21

    Y1 - 2014/10/21

    N2 - The inclusive top quark pair (tt) production cross-section σtt has been measured in proton–proton collisions at √s = 7 TeV and√s = 8 TeV with the ATLAS experiment at the LHC, using tt events with an opposite-charge eμ pair in the final state. The measurement was performed with the 2011 7 TeV dataset corresponding to an integrated luminosity of 4.6 fb−1 and the 2012 8 TeV dataset of 20.3 fb−1. The numbers of events with exactly one and exactly two b-tagged jets were counted and used to simultaneously determine σtt and the efficiency to reconstruct and b-tag a jet from a top quark decay, thereby minimising the associated systematic uncertainties. The cross-section was measured to be: σtt = 182.9 ± 3.1 ± 4.2 ± 3.6 ± 3.3 pb (√s = 7 TeV) and σtt = 242.4 ± 1.7 ± 5.5 ± 7.5 ± 4.2 pb (√s = 8 TeV), where the four uncertainties arise from data statistics, experimental and theoretical systematic effects, knowledge of the integrated luminosity and of the LHC beam energy. The results are consistent with recent theoretical QCD calculations at next-to-next-to-leading order. Fiducial measurements corresponding to the experimental acceptance of the leptons are also reported, together with the ratio of cross-sections measured at the two centre-of-mass energies. The inclusive cross-section results were used to determine the top quark pole mass via the dependence of the theoretically predicted cross-section on mpole t giving a result of mpole t = 172.9+2.5 −2.6 GeV. By looking for an excess of tt production with respect to the QCD prediction, the results were also used to place limits on the pair-production of supersymmetric top squarks t1 with masses close to the top quark mass, decaying via t1 → t χ0 1 to predominantly right-handed top quarks and a light neutralino χ0 1, the lightest supersymmet-ric particle. Top squarks with masses between the top quark mass and 177 GeV are excluded at the 95 % confidence level.

    AB - The inclusive top quark pair (tt) production cross-section σtt has been measured in proton–proton collisions at √s = 7 TeV and√s = 8 TeV with the ATLAS experiment at the LHC, using tt events with an opposite-charge eμ pair in the final state. The measurement was performed with the 2011 7 TeV dataset corresponding to an integrated luminosity of 4.6 fb−1 and the 2012 8 TeV dataset of 20.3 fb−1. The numbers of events with exactly one and exactly two b-tagged jets were counted and used to simultaneously determine σtt and the efficiency to reconstruct and b-tag a jet from a top quark decay, thereby minimising the associated systematic uncertainties. The cross-section was measured to be: σtt = 182.9 ± 3.1 ± 4.2 ± 3.6 ± 3.3 pb (√s = 7 TeV) and σtt = 242.4 ± 1.7 ± 5.5 ± 7.5 ± 4.2 pb (√s = 8 TeV), where the four uncertainties arise from data statistics, experimental and theoretical systematic effects, knowledge of the integrated luminosity and of the LHC beam energy. The results are consistent with recent theoretical QCD calculations at next-to-next-to-leading order. Fiducial measurements corresponding to the experimental acceptance of the leptons are also reported, together with the ratio of cross-sections measured at the two centre-of-mass energies. The inclusive cross-section results were used to determine the top quark pole mass via the dependence of the theoretically predicted cross-section on mpole t giving a result of mpole t = 172.9+2.5 −2.6 GeV. By looking for an excess of tt production with respect to the QCD prediction, the results were also used to place limits on the pair-production of supersymmetric top squarks t1 with masses close to the top quark mass, decaying via t1 → t χ0 1 to predominantly right-handed top quarks and a light neutralino χ0 1, the lightest supersymmet-ric particle. Top squarks with masses between the top quark mass and 177 GeV are excluded at the 95 % confidence level.

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