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| CMS-PAS-HIG-16-034 | ||
| Search for new diboson resonances in the dilepton+jets final state at $\sqrt{s} = $ 13 TeV with 2016 data | ||
| CMS Collaboration | ||
| January 2017 | ||
| Abstract: We present a search for new resonances decaying to a pair of Z bosons where one boson decays hadronically and the other decays into two charged leptons. Results are based on proton-proton collision data corresponding to an integrated luminosity of 12.9 fb$^{-1}$, collected by the CMS experiment at the CERN LHC at a centre-of-mass energy of 13 TeV. We use substructure techniques to identify hadronic jets that come from a single $\mathrm{Z\rightarrow q\bar{q}}$, and use kinematic and flavour information of reconstructed particles to achieve maximum separation between signal and background. Upper limits on resonance production cross-sections at 95% confidence level are set separately for spin-0 and spin-2 resonance hypotheses. The range of excluded cross-sections is 5.0 to 130 fb in the former hypothesis and 3.3 to 110 fb in the latter. | ||
| Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ; | ||
| Figures | |
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Figure 1:
Simulated efficiency for the full set of selection requirements, as function of the generated resonance mass ${m_\mathrm {X}}$, summing over all three categories. Efficiencies are shown for the Higgs boson-like benchmark (left) and the bulk graviton benchmark (right). For the former we distinguish between vector boson fusion production (dotted line) and gluon fusion production (dashed line); for the latter only gluon fusion production is considered. Efficiencies are defined with respect to a $\mathrm{ Z } \mathrm{ Z } \rightarrow \ell \ell \mathrm{ q \bar{q} }$ decay mode, with $\ell = \mathrm{ e },\, \mu $. |
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Figure 1-a:
Simulated efficiency for the full set of selection requirements, as function of the generated resonance mass ${m_\mathrm {X}}$, summing over all three categories. Efficiencies are shown for the Higgs boson-like benchmark. We distinguish between vector boson fusion production (dotted line) and gluon fusion production (dashed line). Efficiencies are defined with respect to a $\mathrm{ Z } \mathrm{ Z } \rightarrow \ell \ell \mathrm{ q \bar{q} }$ decay mode, with $\ell = \mathrm{ e },\, \mu $. |
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Figure 1-b:
Simulated efficiency for the full set of selection requirements, as function of the generated resonance mass ${m_\mathrm {X}}$, summing over all three categories. Efficiencies are shown for the bulk graviton benchmark. Only gluon fusion production is considered. Efficiencies are defined with respect to a $\mathrm{ Z } \mathrm{ Z } \rightarrow \ell \ell \mathrm{ q \bar{q} }$ decay mode, with $\ell = \mathrm{ e },\, \mu $. |
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Figure 2:
Resonance candidate mass ${M_\mathrm {ZZ}}$ in the signal region for the merged (left) and resolved (right) selections, for the untagged (top), b-tagged (middle) and VBF-tagged (bottom) categories. The points are the observed data, the stacked histograms are the standard model simulated background, and the open histograms are simulated signal samples, corresponding to narrow spin-0 resonances produced in gluon fusion ($ {m_\mathrm {X}} = $ 750 GeV) or vector-boson fusion ($ {m_\mathrm {X}} = $ 900 GeV). Events with $ {M_\mathrm {ZZ}}>$ 2.4 TeV are included in the last bin. The dotted lines are the standard model data-driven background estimation, discussed in Sec. 5. Bottom panels show the pulls, defined as the difference of the data and the background estimation in each bin, divided by the standard deviation of the data. |
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Figure 2-a:
Resonance candidate mass ${M_\mathrm {ZZ}}$ in the signal region for the merged selections, for the untagged category. The points are the observed data, the stacked histograms are the standard model simulated background, and the open histograms are simulated signal samples, corresponding to narrow spin-0 resonances produced in gluon fusion ($ {m_\mathrm {X}} = $ 750 GeV) or vector-boson fusion ($ {m_\mathrm {X}} = $ 900 GeV). Events with $ {M_\mathrm {ZZ}}>$ 2.4 TeV are included in the last bin. The dotted lines are the standard model data-driven background estimation, discussed in Sec. 5. The bottom panel shows the pulls, defined as the difference of the data and the background estimation in each bin, divided by the standard deviation of the data. |
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Figure 2-b:
Resonance candidate mass ${M_\mathrm {ZZ}}$ in the signal region for the resolved selections, for the untagged category. The points are the observed data, the stacked histograms are the standard model simulated background, and the open histograms are simulated signal samples, corresponding to narrow spin-0 resonances produced in gluon fusion ($ {m_\mathrm {X}} = $ 750 GeV) or vector-boson fusion ($ {m_\mathrm {X}} = $ 900 GeV). Events with $ {M_\mathrm {ZZ}}>$ 2.4 TeV are included in the last bin. The dotted lines are the standard model data-driven background estimation, discussed in Sec. 5. The bottom panel shows the pulls, defined as the difference of the data and the background estimation in each bin, divided by the standard deviation of the data. |
png pdf |
Figure 2-c:
Resonance candidate mass ${M_\mathrm {ZZ}}$ in the signal region for the merged selections, for the b-tagged category. The points are the observed data, the stacked histograms are the standard model simulated background, and the open histograms are simulated signal samples, corresponding to narrow spin-0 resonances produced in gluon fusion ($ {m_\mathrm {X}} = $ 750 GeV) or vector-boson fusion ($ {m_\mathrm {X}} = $ 900 GeV). Events with $ {M_\mathrm {ZZ}}>$ 2.4 TeV are included in the last bin. The dotted lines are the standard model data-driven background estimation, discussed in Sec. 5. The bottom panel shows the pulls, defined as the difference of the data and the background estimation in each bin, divided by the standard deviation of the data. |
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Figure 2-d:
Resonance candidate mass ${M_\mathrm {ZZ}}$ in the signal region for the resolved selections, for the b-tagged category. The points are the observed data, the stacked histograms are the standard model simulated background, and the open histograms are simulated signal samples, corresponding to narrow spin-0 resonances produced in gluon fusion ($ {m_\mathrm {X}} = $ 750 GeV) or vector-boson fusion ($ {m_\mathrm {X}} = $ 900 GeV). Events with $ {M_\mathrm {ZZ}}>$ 2.4 TeV are included in the last bin. The dotted lines are the standard model data-driven background estimation, discussed in Sec. 5. The bottom panel shows the pulls, defined as the difference of the data and the background estimation in each bin, divided by the standard deviation of the data. |
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Figure 2-e:
Resonance candidate mass ${M_\mathrm {ZZ}}$ in the signal region for the merged selections, for the VBF-tagged category. The points are the observed data, the stacked histograms are the standard model simulated background, and the open histograms are simulated signal samples, corresponding to narrow spin-0 resonances produced in gluon fusion ($ {m_\mathrm {X}} = $ 750 GeV) or vector-boson fusion ($ {m_\mathrm {X}} = $ 900 GeV). Events with $ {M_\mathrm {ZZ}}>$ 2.4 TeV are included in the last bin. The dotted lines are the standard model data-driven background estimation, discussed in Sec. 5. The bottom panel shows the pulls, defined as the difference of the data and the background estimation in each bin, divided by the standard deviation of the data. |
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Figure 2-f:
Resonance candidate mass ${M_\mathrm {ZZ}}$ in the signal region for the resolved selections, for the VBF-tagged category. The points are the observed data, the stacked histograms are the standard model simulated background, and the open histograms are simulated signal samples, corresponding to narrow spin-0 resonances produced in gluon fusion ($ {m_\mathrm {X}} = $ 750 GeV) or vector-boson fusion ($ {m_\mathrm {X}} = $ 900 GeV). Events with $ {M_\mathrm {ZZ}}>$ 2.4 TeV are included in the last bin. The dotted lines are the standard model data-driven background estimation, discussed in Sec. 5. The bottom panel shows the pulls, defined as the difference of the data and the background estimation in each bin, divided by the standard deviation of the data. |
png pdf |
Figure 3:
Top: the discriminant ${\mathcal {D}_\textrm {Zjj}}$ in the signal region for the spin-0 (left) and spin-2 (right) cases, all categories summed. The points are the observed data, the stacked histograms are the standard model simulated background, and the open histograms are simulated signal samples, corresponding to narrow spin-0 resonances produced in gluon fusion ($ {m_\mathrm {X}}{} = $ 750 GeV) or vector-boson fusion ($ {m_\mathrm {X}}{} = $ 900 GeV) in the left plot and a narrow bulk graviton ($ {m_\mathrm {X}}{} = $ 800 GeV) in the right plot. Bottom: the discriminant ${\mathcal {D}_\textrm {2jet}}$ in the signal region for the spin-0 case, all categories summed, using the same notations. The bin at $-1$ corresponds to events with less than 2 extra reconstructed jets, where ${\mathcal {D}_\textrm {2jet}}$ cannot be computed. |
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Figure 3-a:
The discriminant ${\mathcal {D}_\textrm {Zjj}}$ in the signal region for the spin-0 spin-2 case, all categories summed. The points are the observed data, the stacked histograms are the standard model simulated background, and the open histograms are simulated signal samples, corresponding to narrow spin-0 resonances produced in gluon fusion ($ {m_\mathrm {X}}{} = $ 750 GeV) or vector-boson fusion ($ {m_\mathrm {X}}{} = $ 900 GeV). |
png pdf |
Figure 3-b:
The discriminant ${\mathcal {D}_\textrm {Zjj}}$ in the signal region for the spin-0 spin-2 case, all categories summed. The points are the observed data, the stacked histograms are the standard model simulated background, and the open histograms are simulated signal samples, corresponding to a narrow bulk graviton ($ {m_\mathrm {X}}{} = $ 800 GeV) in the right plot. |
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Figure 3-c:
The discriminant ${\mathcal {D}_\textrm {2jet}}$ in the signal region for the spin-0 case, all categories summed, using the same notations. The bin at $-1$ corresponds to events with less than 2 extra reconstructed jets, where ${\mathcal {D}_\textrm {2jet}}$ cannot be computed. |
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Figure 4:
Expected limits (dashed black line) and observed limits (continuous black line) for the cross-section of the process ${\mathrm {X {\rightarrow } {\mathrm {Z}} {\mathrm {Z}}}}$, for a spin-0 resonance (left plot) and spin-2 resonance (right plot) with 550 $ < {m_\mathrm {X}}< $ 2000 GeV. For the spin-0 resonance, the ratio between production by gluon fusion and by vector boson fusion is treated as a nuisance parameter and profiled. |
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Figure 4-a:
Expected limit (dashed black line) and observed limit (continuous black line) for the cross-section of the process ${\mathrm {X {\rightarrow } {\mathrm {Z}} {\mathrm {Z}}}}$, for a spin-0 resonance with 550 $ < {m_\mathrm {X}}< $ 2000 GeV. The ratio between production by gluon fusion and by vector boson fusion is treated as a nuisance parameter and profiled. |
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Figure 4-b:
Expected limit (dashed black line) and observed limit (continuous black line) for the cross-section of the process ${\mathrm {X {\rightarrow } {\mathrm {Z}} {\mathrm {Z}}}}$, for a spin-2 resonance with 550 $ < {m_\mathrm {X}}< $ 2000 GeV. |
| Tables | |
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Table 1:
Summary of selection requirements and categorisation. Signal and sideband regions are defined by ranges in the hadronic Z boson candidate mass ${M( { {\mathrm {Z}}_\textrm {had}})}$, after all other selection criteria are applied. The three last lines describe the categorisation of all selected events. For the arbitration procedure amongst different hadronic Z boson candidates, see text. |
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Table 2:
Summary of systematic uncertainties on the signal normalisation in the resolved and boosted analyses. |
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Table 3:
Summary of systematic uncertainties on the background for each component. |
| Summary |
| A search for diboson resonances in the mass range 550 GeV to 2000 GeV in the semileptonic $ \mathrm{ X } \rightarrow\mathrm{ Z }\mathrm{ Z } \rightarrow \ell^+\ell^- \, \textrm{+ jets} $ final state, where one Z boson decays hadronically, appearing as either one or two jets in the detector, and the other Z decays to two leptons, has been presented. Data corresponding to an integrated luminosity of 12.9 fb$^{-1}$ of proton-proton collisions at centre-of-mass energy of 13 TeV have been analysed. A set of limits on production cross section times decay branching fraction of a scalar boson or spin-2 boson in the model with gravity propagating in the bulk of extra dimensions is obtained. The range of excluded cross-sections is 5.0 to 130 fb in the former hypothesis and 3.3 to 110 fb in the latter. |
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