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| CMS-B2G-24-016 ; CERN-EP-2026-248 | ||
| Search for pair-produced vector-like top quarks decaying into Lorentz-boosted top quarks and scalar bosons in proton-proton collisions at $ \sqrt{s}= $ 13 TeV | ||
| CMS Collaboration | ||
| 2 October 2026 | ||
| Submitted to Physical Review D | ||
| Abstract: A search for pair-produced vector-like top quarks, $ T $, decaying into a new scalar boson $ \phi $ and a standard model (SM) top quark is presented. The search targets events containing a photon pair originating from the decay of one of the scalar bosons, accompanied by all-hadronic decays of the SM top quark pair. The analysis is optimized for boosted top quark signatures in which the decay products of the top quarks are reconstructed as large-radius jets. The search is based on proton-proton collision data at $ \sqrt{s}= $ 13 TeV, collected by the CMS experiment at the CERN LHC during 2016--2018, corresponding to an integrated luminosity of 138 fb$ ^{-1} $. The search is performed for an array of T and $ \phi $ masses. No significant deviation from the predicted background is observed. The largest local excess has a significance of 2.7 standard deviations, reduced to 1.5 standard deviations after accounting for the look-elsewhere effect. Upper limits at 95% confidence level are set on the product of $ T \bar{T}$ production cross section and the branching fraction. | ||
| Links: e-print arXiv:2610.03489 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ; | ||
| Figures | |
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Figure 1:
A representative leading order Feynman diagram for the pair production of vector-like top quarks $ T $ with subsequent $ T \to \phi\mathrm{t} $ decays. |
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Figure 2:
Distribution of reconstructed T candidates in the $ m^\text{reco}_{T } $--$ m^\text{reco}_{\phi} $ plane for data (upper) and simulated $ \mathrm{t}\overline{\mathrm{t}} $ events (lower), shown for the SR (left) and CR (right). The simulated $ \mathrm{t}\overline{\mathrm{t}} $ events are normalized to sum to the total data events in the SR and the CR, respectively. |
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Figure 2-a:
Distribution of reconstructed T candidates in the $ m^\text{reco}_{T } $--$ m^\text{reco}_{\phi} $ plane for data (upper) and simulated $ \mathrm{t}\overline{\mathrm{t}} $ events (lower), shown for the SR (left) and CR (right). The simulated $ \mathrm{t}\overline{\mathrm{t}} $ events are normalized to sum to the total data events in the SR and the CR, respectively. |
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Figure 2-b:
Distribution of reconstructed T candidates in the $ m^\text{reco}_{T } $--$ m^\text{reco}_{\phi} $ plane for data (upper) and simulated $ \mathrm{t}\overline{\mathrm{t}} $ events (lower), shown for the SR (left) and CR (right). The simulated $ \mathrm{t}\overline{\mathrm{t}} $ events are normalized to sum to the total data events in the SR and the CR, respectively. |
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Figure 2-c:
Distribution of reconstructed T candidates in the $ m^\text{reco}_{T } $--$ m^\text{reco}_{\phi} $ plane for data (upper) and simulated $ \mathrm{t}\overline{\mathrm{t}} $ events (lower), shown for the SR (left) and CR (right). The simulated $ \mathrm{t}\overline{\mathrm{t}} $ events are normalized to sum to the total data events in the SR and the CR, respectively. |
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Figure 2-d:
Distribution of reconstructed T candidates in the $ m^\text{reco}_{T } $--$ m^\text{reco}_{\phi} $ plane for data (upper) and simulated $ \mathrm{t}\overline{\mathrm{t}} $ events (lower), shown for the SR (left) and CR (right). The simulated $ \mathrm{t}\overline{\mathrm{t}} $ events are normalized to sum to the total data events in the SR and the CR, respectively. |
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Figure 3:
Comparison of data and postfit background predictions from the background-only fit in the VR. The VR-CR (left) and VR-SR (right) regions are shown. The distributions are projected onto $ m^\text{reco}_{T } $ in three intervals of $ m^\text{reco}_{\phi} $: 25 $ < m^\text{reco}_{\phi} < $ 75 GeV (upper), 75 $ < m^\text{reco}_{\phi} < $ 325 GeV (middle), and 325 $ < m^\text{reco}_{\phi} < $ 825 GeV (lower). The $ \mathrm{t}\overline{\mathrm{t}} $ component scaled by the transfer function is shown in red and the $ \mathrm{W}/\mathrm{Z} $+jets contribution in green. The lower panels show the difference between the data and the background normalized by the uncertainty. |
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Figure 3-a:
Comparison of data and postfit background predictions from the background-only fit in the VR. The VR-CR (left) and VR-SR (right) regions are shown. The distributions are projected onto $ m^\text{reco}_{T } $ in three intervals of $ m^\text{reco}_{\phi} $: 25 $ < m^\text{reco}_{\phi} < $ 75 GeV (upper), 75 $ < m^\text{reco}_{\phi} < $ 325 GeV (middle), and 325 $ < m^\text{reco}_{\phi} < $ 825 GeV (lower). The $ \mathrm{t}\overline{\mathrm{t}} $ component scaled by the transfer function is shown in red and the $ \mathrm{W}/\mathrm{Z} $+jets contribution in green. The lower panels show the difference between the data and the background normalized by the uncertainty. |
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Figure 3-b:
Comparison of data and postfit background predictions from the background-only fit in the VR. The VR-CR (left) and VR-SR (right) regions are shown. The distributions are projected onto $ m^\text{reco}_{T } $ in three intervals of $ m^\text{reco}_{\phi} $: 25 $ < m^\text{reco}_{\phi} < $ 75 GeV (upper), 75 $ < m^\text{reco}_{\phi} < $ 325 GeV (middle), and 325 $ < m^\text{reco}_{\phi} < $ 825 GeV (lower). The $ \mathrm{t}\overline{\mathrm{t}} $ component scaled by the transfer function is shown in red and the $ \mathrm{W}/\mathrm{Z} $+jets contribution in green. The lower panels show the difference between the data and the background normalized by the uncertainty. |
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Figure 3-c:
Comparison of data and postfit background predictions from the background-only fit in the VR. The VR-CR (left) and VR-SR (right) regions are shown. The distributions are projected onto $ m^\text{reco}_{T } $ in three intervals of $ m^\text{reco}_{\phi} $: 25 $ < m^\text{reco}_{\phi} < $ 75 GeV (upper), 75 $ < m^\text{reco}_{\phi} < $ 325 GeV (middle), and 325 $ < m^\text{reco}_{\phi} < $ 825 GeV (lower). The $ \mathrm{t}\overline{\mathrm{t}} $ component scaled by the transfer function is shown in red and the $ \mathrm{W}/\mathrm{Z} $+jets contribution in green. The lower panels show the difference between the data and the background normalized by the uncertainty. |
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Figure 3-d:
Comparison of data and postfit background predictions from the background-only fit in the VR. The VR-CR (left) and VR-SR (right) regions are shown. The distributions are projected onto $ m^\text{reco}_{T } $ in three intervals of $ m^\text{reco}_{\phi} $: 25 $ < m^\text{reco}_{\phi} < $ 75 GeV (upper), 75 $ < m^\text{reco}_{\phi} < $ 325 GeV (middle), and 325 $ < m^\text{reco}_{\phi} < $ 825 GeV (lower). The $ \mathrm{t}\overline{\mathrm{t}} $ component scaled by the transfer function is shown in red and the $ \mathrm{W}/\mathrm{Z} $+jets contribution in green. The lower panels show the difference between the data and the background normalized by the uncertainty. |
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Figure 3-e:
Comparison of data and postfit background predictions from the background-only fit in the VR. The VR-CR (left) and VR-SR (right) regions are shown. The distributions are projected onto $ m^\text{reco}_{T } $ in three intervals of $ m^\text{reco}_{\phi} $: 25 $ < m^\text{reco}_{\phi} < $ 75 GeV (upper), 75 $ < m^\text{reco}_{\phi} < $ 325 GeV (middle), and 325 $ < m^\text{reco}_{\phi} < $ 825 GeV (lower). The $ \mathrm{t}\overline{\mathrm{t}} $ component scaled by the transfer function is shown in red and the $ \mathrm{W}/\mathrm{Z} $+jets contribution in green. The lower panels show the difference between the data and the background normalized by the uncertainty. |
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Figure 3-f:
Comparison of data and postfit background predictions from the background-only fit in the VR. The VR-CR (left) and VR-SR (right) regions are shown. The distributions are projected onto $ m^\text{reco}_{T } $ in three intervals of $ m^\text{reco}_{\phi} $: 25 $ < m^\text{reco}_{\phi} < $ 75 GeV (upper), 75 $ < m^\text{reco}_{\phi} < $ 325 GeV (middle), and 325 $ < m^\text{reco}_{\phi} < $ 825 GeV (lower). The $ \mathrm{t}\overline{\mathrm{t}} $ component scaled by the transfer function is shown in red and the $ \mathrm{W}/\mathrm{Z} $+jets contribution in green. The lower panels show the difference between the data and the background normalized by the uncertainty. |
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Figure 4:
Comparison of data and postfit background predictions from the background-only fit in the VR. The VR-CR (left) and VR-SR (right) regions are shown. The distributions are projected onto $ m^\text{reco}_{\phi} $ in three intervals of $ m^\text{reco}_{T } $: 625 $ < m^\text{reco}_{T } < $ 825 GeV (upper), 825 $ < m^\text{reco}_{T } < $ 1125 GeV (middle), and 1125 $ < m^\text{reco}_{T } < $ 1525 GeV (lower). The $ \mathrm{t}\overline{\mathrm{t}} $ component scaled by the transfer function is shown in red and the $ \mathrm{W}/\mathrm{Z} $+jets contribution in green. The lower panels show the difference between the data and the background normalized by the uncertainty. |
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Figure 4-a:
Comparison of data and postfit background predictions from the background-only fit in the VR. The VR-CR (left) and VR-SR (right) regions are shown. The distributions are projected onto $ m^\text{reco}_{\phi} $ in three intervals of $ m^\text{reco}_{T } $: 625 $ < m^\text{reco}_{T } < $ 825 GeV (upper), 825 $ < m^\text{reco}_{T } < $ 1125 GeV (middle), and 1125 $ < m^\text{reco}_{T } < $ 1525 GeV (lower). The $ \mathrm{t}\overline{\mathrm{t}} $ component scaled by the transfer function is shown in red and the $ \mathrm{W}/\mathrm{Z} $+jets contribution in green. The lower panels show the difference between the data and the background normalized by the uncertainty. |
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Figure 4-b:
Comparison of data and postfit background predictions from the background-only fit in the VR. The VR-CR (left) and VR-SR (right) regions are shown. The distributions are projected onto $ m^\text{reco}_{\phi} $ in three intervals of $ m^\text{reco}_{T } $: 625 $ < m^\text{reco}_{T } < $ 825 GeV (upper), 825 $ < m^\text{reco}_{T } < $ 1125 GeV (middle), and 1125 $ < m^\text{reco}_{T } < $ 1525 GeV (lower). The $ \mathrm{t}\overline{\mathrm{t}} $ component scaled by the transfer function is shown in red and the $ \mathrm{W}/\mathrm{Z} $+jets contribution in green. The lower panels show the difference between the data and the background normalized by the uncertainty. |
png pdf |
Figure 4-c:
Comparison of data and postfit background predictions from the background-only fit in the VR. The VR-CR (left) and VR-SR (right) regions are shown. The distributions are projected onto $ m^\text{reco}_{\phi} $ in three intervals of $ m^\text{reco}_{T } $: 625 $ < m^\text{reco}_{T } < $ 825 GeV (upper), 825 $ < m^\text{reco}_{T } < $ 1125 GeV (middle), and 1125 $ < m^\text{reco}_{T } < $ 1525 GeV (lower). The $ \mathrm{t}\overline{\mathrm{t}} $ component scaled by the transfer function is shown in red and the $ \mathrm{W}/\mathrm{Z} $+jets contribution in green. The lower panels show the difference between the data and the background normalized by the uncertainty. |
png pdf |
Figure 4-d:
Comparison of data and postfit background predictions from the background-only fit in the VR. The VR-CR (left) and VR-SR (right) regions are shown. The distributions are projected onto $ m^\text{reco}_{\phi} $ in three intervals of $ m^\text{reco}_{T } $: 625 $ < m^\text{reco}_{T } < $ 825 GeV (upper), 825 $ < m^\text{reco}_{T } < $ 1125 GeV (middle), and 1125 $ < m^\text{reco}_{T } < $ 1525 GeV (lower). The $ \mathrm{t}\overline{\mathrm{t}} $ component scaled by the transfer function is shown in red and the $ \mathrm{W}/\mathrm{Z} $+jets contribution in green. The lower panels show the difference between the data and the background normalized by the uncertainty. |
png pdf |
Figure 4-e:
Comparison of data and postfit background predictions from the background-only fit in the VR. The VR-CR (left) and VR-SR (right) regions are shown. The distributions are projected onto $ m^\text{reco}_{\phi} $ in three intervals of $ m^\text{reco}_{T } $: 625 $ < m^\text{reco}_{T } < $ 825 GeV (upper), 825 $ < m^\text{reco}_{T } < $ 1125 GeV (middle), and 1125 $ < m^\text{reco}_{T } < $ 1525 GeV (lower). The $ \mathrm{t}\overline{\mathrm{t}} $ component scaled by the transfer function is shown in red and the $ \mathrm{W}/\mathrm{Z} $+jets contribution in green. The lower panels show the difference between the data and the background normalized by the uncertainty. |
png pdf |
Figure 4-f:
Comparison of data and postfit background predictions from the background-only fit in the VR. The VR-CR (left) and VR-SR (right) regions are shown. The distributions are projected onto $ m^\text{reco}_{\phi} $ in three intervals of $ m^\text{reco}_{T } $: 625 $ < m^\text{reco}_{T } < $ 825 GeV (upper), 825 $ < m^\text{reco}_{T } < $ 1125 GeV (middle), and 1125 $ < m^\text{reco}_{T } < $ 1525 GeV (lower). The $ \mathrm{t}\overline{\mathrm{t}} $ component scaled by the transfer function is shown in red and the $ \mathrm{W}/\mathrm{Z} $+jets contribution in green. The lower panels show the difference between the data and the background normalized by the uncertainty. |
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Figure 5:
Comparison of the data and postfit background predictions projected onto $ m^\text{reco}_{T } $ for the signal hypothesis $ m_{T }= $ 900 GeV and $ m_{\phi}= $ 150 GeV. The CR (left) and SR (right) regions are shown. The distributions are shown in three intervals of $ m^\text{reco}_{\phi} $: 25 $ < m^\text{reco}_{\phi} < $ 75 GeV (upper), 75 $ < m^\text{reco}_{\phi} < $ 325 GeV (middle), and 325 $ < m^\text{reco}_{\phi} < $ 825 GeV (lower). The transferred $ \mathrm{t}\overline{\mathrm{t}} $ contribution is shown in red and the $ \mathrm{W}/\mathrm{Z} $+jets contribution in green. The signal distribution is overlaid as a blue line. The shaded band represents the uncertainty in the total background predictions at 95% confidence level. The lower panels show the difference between the data and the background normalized by the uncertainty. |
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Figure 5-a:
Comparison of the data and postfit background predictions projected onto $ m^\text{reco}_{T } $ for the signal hypothesis $ m_{T }= $ 900 GeV and $ m_{\phi}= $ 150 GeV. The CR (left) and SR (right) regions are shown. The distributions are shown in three intervals of $ m^\text{reco}_{\phi} $: 25 $ < m^\text{reco}_{\phi} < $ 75 GeV (upper), 75 $ < m^\text{reco}_{\phi} < $ 325 GeV (middle), and 325 $ < m^\text{reco}_{\phi} < $ 825 GeV (lower). The transferred $ \mathrm{t}\overline{\mathrm{t}} $ contribution is shown in red and the $ \mathrm{W}/\mathrm{Z} $+jets contribution in green. The signal distribution is overlaid as a blue line. The shaded band represents the uncertainty in the total background predictions at 95% confidence level. The lower panels show the difference between the data and the background normalized by the uncertainty. |
png pdf |
Figure 5-b:
Comparison of the data and postfit background predictions projected onto $ m^\text{reco}_{T } $ for the signal hypothesis $ m_{T }= $ 900 GeV and $ m_{\phi}= $ 150 GeV. The CR (left) and SR (right) regions are shown. The distributions are shown in three intervals of $ m^\text{reco}_{\phi} $: 25 $ < m^\text{reco}_{\phi} < $ 75 GeV (upper), 75 $ < m^\text{reco}_{\phi} < $ 325 GeV (middle), and 325 $ < m^\text{reco}_{\phi} < $ 825 GeV (lower). The transferred $ \mathrm{t}\overline{\mathrm{t}} $ contribution is shown in red and the $ \mathrm{W}/\mathrm{Z} $+jets contribution in green. The signal distribution is overlaid as a blue line. The shaded band represents the uncertainty in the total background predictions at 95% confidence level. The lower panels show the difference between the data and the background normalized by the uncertainty. |
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Figure 5-c:
Comparison of the data and postfit background predictions projected onto $ m^\text{reco}_{T } $ for the signal hypothesis $ m_{T }= $ 900 GeV and $ m_{\phi}= $ 150 GeV. The CR (left) and SR (right) regions are shown. The distributions are shown in three intervals of $ m^\text{reco}_{\phi} $: 25 $ < m^\text{reco}_{\phi} < $ 75 GeV (upper), 75 $ < m^\text{reco}_{\phi} < $ 325 GeV (middle), and 325 $ < m^\text{reco}_{\phi} < $ 825 GeV (lower). The transferred $ \mathrm{t}\overline{\mathrm{t}} $ contribution is shown in red and the $ \mathrm{W}/\mathrm{Z} $+jets contribution in green. The signal distribution is overlaid as a blue line. The shaded band represents the uncertainty in the total background predictions at 95% confidence level. The lower panels show the difference between the data and the background normalized by the uncertainty. |
png pdf |
Figure 5-d:
Comparison of the data and postfit background predictions projected onto $ m^\text{reco}_{T } $ for the signal hypothesis $ m_{T }= $ 900 GeV and $ m_{\phi}= $ 150 GeV. The CR (left) and SR (right) regions are shown. The distributions are shown in three intervals of $ m^\text{reco}_{\phi} $: 25 $ < m^\text{reco}_{\phi} < $ 75 GeV (upper), 75 $ < m^\text{reco}_{\phi} < $ 325 GeV (middle), and 325 $ < m^\text{reco}_{\phi} < $ 825 GeV (lower). The transferred $ \mathrm{t}\overline{\mathrm{t}} $ contribution is shown in red and the $ \mathrm{W}/\mathrm{Z} $+jets contribution in green. The signal distribution is overlaid as a blue line. The shaded band represents the uncertainty in the total background predictions at 95% confidence level. The lower panels show the difference between the data and the background normalized by the uncertainty. |
png pdf |
Figure 5-e:
Comparison of the data and postfit background predictions projected onto $ m^\text{reco}_{T } $ for the signal hypothesis $ m_{T }= $ 900 GeV and $ m_{\phi}= $ 150 GeV. The CR (left) and SR (right) regions are shown. The distributions are shown in three intervals of $ m^\text{reco}_{\phi} $: 25 $ < m^\text{reco}_{\phi} < $ 75 GeV (upper), 75 $ < m^\text{reco}_{\phi} < $ 325 GeV (middle), and 325 $ < m^\text{reco}_{\phi} < $ 825 GeV (lower). The transferred $ \mathrm{t}\overline{\mathrm{t}} $ contribution is shown in red and the $ \mathrm{W}/\mathrm{Z} $+jets contribution in green. The signal distribution is overlaid as a blue line. The shaded band represents the uncertainty in the total background predictions at 95% confidence level. The lower panels show the difference between the data and the background normalized by the uncertainty. |
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Figure 5-f:
Comparison of the data and postfit background predictions projected onto $ m^\text{reco}_{T } $ for the signal hypothesis $ m_{T }= $ 900 GeV and $ m_{\phi}= $ 150 GeV. The CR (left) and SR (right) regions are shown. The distributions are shown in three intervals of $ m^\text{reco}_{\phi} $: 25 $ < m^\text{reco}_{\phi} < $ 75 GeV (upper), 75 $ < m^\text{reco}_{\phi} < $ 325 GeV (middle), and 325 $ < m^\text{reco}_{\phi} < $ 825 GeV (lower). The transferred $ \mathrm{t}\overline{\mathrm{t}} $ contribution is shown in red and the $ \mathrm{W}/\mathrm{Z} $+jets contribution in green. The signal distribution is overlaid as a blue line. The shaded band represents the uncertainty in the total background predictions at 95% confidence level. The lower panels show the difference between the data and the background normalized by the uncertainty. |
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Figure 6:
Comparison of the data and postfit background predictions projected onto $ m^\text{reco}_{\phi} $ for the signal hypothesis $ m_{T }= $ 900 GeV and $ m_{\phi}= $ 150 GeV. The CR (left) and SR (right) regions are shown. The distributions are shown in three intervals of $ m^\text{reco}_{T } $: 625 $ < m^\text{reco}_{T } < $ 825 GeV (upper), 825 $ < m^\text{reco}_{T } < $ 1125 GeV (middle), and 1125 $ < m^\text{reco}_{T } < $ 1525 GeV (lower). The transferred $ \mathrm{t}\overline{\mathrm{t}} $ contribution is shown in red and the $ \mathrm{W}/\mathrm{Z} $+jets contribution in green. The signal distribution is overlaid as a blue line. The shaded band represents the uncertainty in the total background predictions at 95% confidence level. The lower panels show the difference between the data and the background normalized by the uncertainty. |
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Figure 6-a:
Comparison of the data and postfit background predictions projected onto $ m^\text{reco}_{\phi} $ for the signal hypothesis $ m_{T }= $ 900 GeV and $ m_{\phi}= $ 150 GeV. The CR (left) and SR (right) regions are shown. The distributions are shown in three intervals of $ m^\text{reco}_{T } $: 625 $ < m^\text{reco}_{T } < $ 825 GeV (upper), 825 $ < m^\text{reco}_{T } < $ 1125 GeV (middle), and 1125 $ < m^\text{reco}_{T } < $ 1525 GeV (lower). The transferred $ \mathrm{t}\overline{\mathrm{t}} $ contribution is shown in red and the $ \mathrm{W}/\mathrm{Z} $+jets contribution in green. The signal distribution is overlaid as a blue line. The shaded band represents the uncertainty in the total background predictions at 95% confidence level. The lower panels show the difference between the data and the background normalized by the uncertainty. |
png pdf |
Figure 6-b:
Comparison of the data and postfit background predictions projected onto $ m^\text{reco}_{\phi} $ for the signal hypothesis $ m_{T }= $ 900 GeV and $ m_{\phi}= $ 150 GeV. The CR (left) and SR (right) regions are shown. The distributions are shown in three intervals of $ m^\text{reco}_{T } $: 625 $ < m^\text{reco}_{T } < $ 825 GeV (upper), 825 $ < m^\text{reco}_{T } < $ 1125 GeV (middle), and 1125 $ < m^\text{reco}_{T } < $ 1525 GeV (lower). The transferred $ \mathrm{t}\overline{\mathrm{t}} $ contribution is shown in red and the $ \mathrm{W}/\mathrm{Z} $+jets contribution in green. The signal distribution is overlaid as a blue line. The shaded band represents the uncertainty in the total background predictions at 95% confidence level. The lower panels show the difference between the data and the background normalized by the uncertainty. |
png pdf |
Figure 6-c:
Comparison of the data and postfit background predictions projected onto $ m^\text{reco}_{\phi} $ for the signal hypothesis $ m_{T }= $ 900 GeV and $ m_{\phi}= $ 150 GeV. The CR (left) and SR (right) regions are shown. The distributions are shown in three intervals of $ m^\text{reco}_{T } $: 625 $ < m^\text{reco}_{T } < $ 825 GeV (upper), 825 $ < m^\text{reco}_{T } < $ 1125 GeV (middle), and 1125 $ < m^\text{reco}_{T } < $ 1525 GeV (lower). The transferred $ \mathrm{t}\overline{\mathrm{t}} $ contribution is shown in red and the $ \mathrm{W}/\mathrm{Z} $+jets contribution in green. The signal distribution is overlaid as a blue line. The shaded band represents the uncertainty in the total background predictions at 95% confidence level. The lower panels show the difference between the data and the background normalized by the uncertainty. |
png pdf |
Figure 6-d:
Comparison of the data and postfit background predictions projected onto $ m^\text{reco}_{\phi} $ for the signal hypothesis $ m_{T }= $ 900 GeV and $ m_{\phi}= $ 150 GeV. The CR (left) and SR (right) regions are shown. The distributions are shown in three intervals of $ m^\text{reco}_{T } $: 625 $ < m^\text{reco}_{T } < $ 825 GeV (upper), 825 $ < m^\text{reco}_{T } < $ 1125 GeV (middle), and 1125 $ < m^\text{reco}_{T } < $ 1525 GeV (lower). The transferred $ \mathrm{t}\overline{\mathrm{t}} $ contribution is shown in red and the $ \mathrm{W}/\mathrm{Z} $+jets contribution in green. The signal distribution is overlaid as a blue line. The shaded band represents the uncertainty in the total background predictions at 95% confidence level. The lower panels show the difference between the data and the background normalized by the uncertainty. |
png pdf |
Figure 6-e:
Comparison of the data and postfit background predictions projected onto $ m^\text{reco}_{\phi} $ for the signal hypothesis $ m_{T }= $ 900 GeV and $ m_{\phi}= $ 150 GeV. The CR (left) and SR (right) regions are shown. The distributions are shown in three intervals of $ m^\text{reco}_{T } $: 625 $ < m^\text{reco}_{T } < $ 825 GeV (upper), 825 $ < m^\text{reco}_{T } < $ 1125 GeV (middle), and 1125 $ < m^\text{reco}_{T } < $ 1525 GeV (lower). The transferred $ \mathrm{t}\overline{\mathrm{t}} $ contribution is shown in red and the $ \mathrm{W}/\mathrm{Z} $+jets contribution in green. The signal distribution is overlaid as a blue line. The shaded band represents the uncertainty in the total background predictions at 95% confidence level. The lower panels show the difference between the data and the background normalized by the uncertainty. |
png pdf |
Figure 6-f:
Comparison of the data and postfit background predictions projected onto $ m^\text{reco}_{\phi} $ for the signal hypothesis $ m_{T }= $ 900 GeV and $ m_{\phi}= $ 150 GeV. The CR (left) and SR (right) regions are shown. The distributions are shown in three intervals of $ m^\text{reco}_{T } $: 625 $ < m^\text{reco}_{T } < $ 825 GeV (upper), 825 $ < m^\text{reco}_{T } < $ 1125 GeV (middle), and 1125 $ < m^\text{reco}_{T } < $ 1525 GeV (lower). The transferred $ \mathrm{t}\overline{\mathrm{t}} $ contribution is shown in red and the $ \mathrm{W}/\mathrm{Z} $+jets contribution in green. The signal distribution is overlaid as a blue line. The shaded band represents the uncertainty in the total background predictions at 95% confidence level. The lower panels show the difference between the data and the background normalized by the uncertainty. |
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Figure 7:
Expected (upper) and observed (lower) upper limits on $ \sigma_{T T } \ \mathcal{B}(T \to \phi \mathrm{t})^2 \ \mathcal{B}_{\gamma\gamma} (2 - \mathcal{B}_{\gamma\gamma}) $ in the $ (m_{T }, m_{\phi}) $ plane where $ \mathcal{B}_{\gamma\gamma} \equiv \mathcal{B}(\phi \to \gamma\gamma) $ is the branching fraction for $ \phi $ decay to two photons. The uncertainty for the expected upper limits is shown in parentheses. |
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Figure 7-a:
Expected (upper) and observed (lower) upper limits on $ \sigma_{T T } \ \mathcal{B}(T \to \phi \mathrm{t})^2 \ \mathcal{B}_{\gamma\gamma} (2 - \mathcal{B}_{\gamma\gamma}) $ in the $ (m_{T }, m_{\phi}) $ plane where $ \mathcal{B}_{\gamma\gamma} \equiv \mathcal{B}(\phi \to \gamma\gamma) $ is the branching fraction for $ \phi $ decay to two photons. The uncertainty for the expected upper limits is shown in parentheses. |
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Figure 7-b:
Expected (upper) and observed (lower) upper limits on $ \sigma_{T T } \ \mathcal{B}(T \to \phi \mathrm{t})^2 \ \mathcal{B}_{\gamma\gamma} (2 - \mathcal{B}_{\gamma\gamma}) $ in the $ (m_{T }, m_{\phi}) $ plane where $ \mathcal{B}_{\gamma\gamma} \equiv \mathcal{B}(\phi \to \gamma\gamma) $ is the branching fraction for $ \phi $ decay to two photons. The uncertainty for the expected upper limits is shown in parentheses. |
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Figure 8:
Expected (dashed) and observed (solid) upper limits on $ \sigma_{T T } \ \mathcal{B}(T \to \phi \mathrm{t})^2 \ \mathcal{B}_{\gamma\gamma} (2 - \mathcal{B}_{\gamma\gamma}) $ as a function of $ m_{T } $ for different values of $ m_{\phi} $. The first row shows $ m_{\phi}= $ 100 and 150 GeV (left to right), the second row shows $ m_{\phi}= $ 200 and 250 GeV (left to right), and the third row shows $ m_{\phi}= $ 300 GeV. The product of the theoretical cross section and the $ \phi $ branching fraction is shown for $ \mathcal{B}_{\gamma\gamma} = $ 0.004 (magenta). |
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Figure 8-a:
Expected (dashed) and observed (solid) upper limits on $ \sigma_{T T } \ \mathcal{B}(T \to \phi \mathrm{t})^2 \ \mathcal{B}_{\gamma\gamma} (2 - \mathcal{B}_{\gamma\gamma}) $ as a function of $ m_{T } $ for different values of $ m_{\phi} $. The first row shows $ m_{\phi}= $ 100 and 150 GeV (left to right), the second row shows $ m_{\phi}= $ 200 and 250 GeV (left to right), and the third row shows $ m_{\phi}= $ 300 GeV. The product of the theoretical cross section and the $ \phi $ branching fraction is shown for $ \mathcal{B}_{\gamma\gamma} = $ 0.004 (magenta). |
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Figure 8-b:
Expected (dashed) and observed (solid) upper limits on $ \sigma_{T T } \ \mathcal{B}(T \to \phi \mathrm{t})^2 \ \mathcal{B}_{\gamma\gamma} (2 - \mathcal{B}_{\gamma\gamma}) $ as a function of $ m_{T } $ for different values of $ m_{\phi} $. The first row shows $ m_{\phi}= $ 100 and 150 GeV (left to right), the second row shows $ m_{\phi}= $ 200 and 250 GeV (left to right), and the third row shows $ m_{\phi}= $ 300 GeV. The product of the theoretical cross section and the $ \phi $ branching fraction is shown for $ \mathcal{B}_{\gamma\gamma} = $ 0.004 (magenta). |
png pdf |
Figure 8-c:
Expected (dashed) and observed (solid) upper limits on $ \sigma_{T T } \ \mathcal{B}(T \to \phi \mathrm{t})^2 \ \mathcal{B}_{\gamma\gamma} (2 - \mathcal{B}_{\gamma\gamma}) $ as a function of $ m_{T } $ for different values of $ m_{\phi} $. The first row shows $ m_{\phi}= $ 100 and 150 GeV (left to right), the second row shows $ m_{\phi}= $ 200 and 250 GeV (left to right), and the third row shows $ m_{\phi}= $ 300 GeV. The product of the theoretical cross section and the $ \phi $ branching fraction is shown for $ \mathcal{B}_{\gamma\gamma} = $ 0.004 (magenta). |
png pdf |
Figure 8-d:
Expected (dashed) and observed (solid) upper limits on $ \sigma_{T T } \ \mathcal{B}(T \to \phi \mathrm{t})^2 \ \mathcal{B}_{\gamma\gamma} (2 - \mathcal{B}_{\gamma\gamma}) $ as a function of $ m_{T } $ for different values of $ m_{\phi} $. The first row shows $ m_{\phi}= $ 100 and 150 GeV (left to right), the second row shows $ m_{\phi}= $ 200 and 250 GeV (left to right), and the third row shows $ m_{\phi}= $ 300 GeV. The product of the theoretical cross section and the $ \phi $ branching fraction is shown for $ \mathcal{B}_{\gamma\gamma} = $ 0.004 (magenta). |
png pdf |
Figure 8-e:
Expected (dashed) and observed (solid) upper limits on $ \sigma_{T T } \ \mathcal{B}(T \to \phi \mathrm{t})^2 \ \mathcal{B}_{\gamma\gamma} (2 - \mathcal{B}_{\gamma\gamma}) $ as a function of $ m_{T } $ for different values of $ m_{\phi} $. The first row shows $ m_{\phi}= $ 100 and 150 GeV (left to right), the second row shows $ m_{\phi}= $ 200 and 250 GeV (left to right), and the third row shows $ m_{\phi}= $ 300 GeV. The product of the theoretical cross section and the $ \phi $ branching fraction is shown for $ \mathcal{B}_{\gamma\gamma} = $ 0.004 (magenta). |
| Tables | |
png pdf |
Table 1:
The baseline, signal region, and control region event selection. |
png pdf |
Table 2:
Largest postfit relative impacts of the dominant systematic uncertainties on the fitted signal-strength parameter $ r $ for mass point ($ m_{T }= $ 900 GeV,$ m_{\phi}= $ 150 GeV). |
| Summary |
| A search for the pair production of vector-like top quarks $ T $ in a scenario involving an additional scalar boson has been presented. The search uses proton-proton collision data collected by the CMS experiment at the LHC during 2016--2018, at center-of-mass energy 13 TeV, corresponding to an integrated luminosity of 138 fb$ ^{-1} $. The analysis considers $ T \bar{T}$ production, with each $ T $ decaying into a standard model top quark and a scalar boson $ \phi $. The top quarks are required to decay hadronically, and one of the scalar bosons is required to decay to a pair of photons. The top quarks are reconstructed as large-radius jets and identified using a ParticleNet discriminant, while a multivariate discriminant is used for photon identification. The background in the signal region is predicted from the distribution of data in a $ \mathrm{t}\overline{\mathrm{t}} $ control region via a transfer function. No significant deviation from the background prediction is observed. The largest local excess has a significance of 2.7 standard deviations, reduced to 1.5 standard deviations after accounting for the look-elsewhere effect. This is the first exclusive search for pair-produced $ T $ quarks in the boosted regime. |
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