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A search for $ t\overline{t} $ resonances using lepton-plus-jets events in proton-proton collisions at $ \sqrt{s}=8 $ TeV with the ATLAS detector

The ATLAS collaboration
JHEP 1508 (2015) 148, 2015

Abstract (data abstract)
A search for new particles that decay into top quark pairs is reported. The search is performed with the ATLAS experiment at the LHC using an integrated luminosity of 20.3 fb-1 of proton-proton collision data collected at a centre-of-mass energy of $\sqrt{s}= 8$ TeV. The lepton-plus-jets final state is used, where the top pair decays to $W^+bW^-\bar{b}$, with one W boson decaying leptonically and the other hadronically. The invariant mass spectrum of top quark pairs is examined for local excesses or deficits that are inconsistent with the Standard Model predictions. No evidence for a top quark pair resonance is found, and 95% confidence-level limits on the production rate are determined for massive states in benchmark models. The upper limits on the cross-section times branching ratio of a narrow Z' boson decaying to top pairs range from 4.2 pb to 0.03 pb for resonance masses from 0.4 TeV to 3.0 TeV. A narrow leptophobic topcolour Z' boson with mass below 1.8 TeV is excluded. Upper limits are set on the cross-section times branching ratio for a broad colour-octet resonance with $\Gamma$/m= 15% decaying to $t\bar{t}$. These range from 2.5 pb to 0.03 pb for masses from 0.4 TeV to 3.0 TeV. A Kaluza-Klein excitation of the gluon in a Randall-Sundrum model is excluded for masses below 2.2 TeV.

  • Table 1

    Data from Figure 1a

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    Selection efficiency x Acceptance for a Z' resonance.

  • Table 2

    Data from Figure 1b

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    Selection efficiency x Acceptance for a KK gluon resonance.

  • Table 3

    Data from Figure 1c

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    Selection efficiency x Acceptance for a KK graviton resonance.

  • Table 4

    Data from Figure 1d

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    Selection efficiency x Acceptance for a spin-0 resonance.

  • Table 5

    Data from Figure 10a

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    Reconstructed m_tt spectrum for the boosted selections.

  • Table 6

    Data from Figure 10b

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    Reconstructed m_tt spectrum for the resolved selections.

  • Table 7

    Data from Figure 10c

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    Reconstructed m_tt spectrum for the all the selections.

  • Table 8

    Data from Figure 11a

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    Limits on the production cross-section x branching ratio to tt final states as a function of the mass of Z'TC2.

  • Table 9

    Data from Figure 11c

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    Limits on the production cross-section x branching ratio to tt final states as a function of the mass of bulk...

  • Table 10

    Data from Figure 11b

    10.17182/hepdata.70548.v1/t10

    Limits on the production cross-section x branching ratio to tt final states as a function of the mass of bulk...

  • Table 11

    Data from Figure 11d

    10.17182/hepdata.70548.v1/t11

    Limits on the production cross-section x branching ratio to tt final states as a function of the mass of a...

  • Table 12

    Data from Figure 12a

    10.17182/hepdata.70548.v1/t12

    Limits on the production cross-section x branching ratio to tt final states as a function of the width of a...

  • Table 13

    Data from Figure 13a

    10.17182/hepdata.70548.v1/t13

    Limits on the production cross-section x branching ratio to tt final states as a function of the width of a...

  • Table 14

    Data from Figure 14a

    10.17182/hepdata.70548.v1/t14

    Limits on the production cross-section x branching ratio to tt final states as a function of the width of a...

  • Table 15

    Data from Figure Aux. 3

    10.17182/hepdata.70548.v1/t15

    Migration from the true mtt values to the reconstructed mtt values for the resolved selection.

  • Table 16

    Data from Figure Aux. 4

    10.17182/hepdata.70548.v1/t16

    Migration from the true mtt values to the reconstructed mtt values for the boosted selection.

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