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| CMS-PAS-FTR-21-001 | ||
| Prospects for the measurement of vector boson scattering production in leptonic W$^\pm$W$^\pm$ and WZ diboson events at $\sqrt{s}= $ 14 TeV at the High-Luminosity LHC | ||
| CMS Collaboration | ||
| July 2021 | ||
| Abstract: Prospects for measuring the W$^\pm$W$^\pm$ and WZ electroweak vector boson scattering processes are studied. The measurements are performed in the leptonic decay modes W$^\pm$W$^\pm$ $ \to \ell^\pm\nu\ell'^\pm\nu$ and WZ $ \to \ell\nu\ell'\ell'$, where $\ell, \ell' = $ e, $\mu$. The analysis is based on existing measurements at $\sqrt{s}$ = 13 TeV, that are extrapolated to the full integrated luminosity at the High-Luminosity LHC at $\sqrt{s} =$ 14 TeV. | ||
| Links: CDS record (PDF) ; CADI line (restricted) ; | ||
| Figures | |
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Figure 1:
Representative Feynman diagrams of a VBS process contributing to the EW-induced production of events containing W$^\pm$W$^\pm$ (left) and WZ (right) boson pairs decaying to leptons, and two forward jets. |
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Figure 1-a:
Representative Feynman diagrams of a VBS process contributing to the EW-induced production of events containing W$^\pm$W$^\pm$ (left) and WZ (right) boson pairs decaying to leptons, and two forward jets. |
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Figure 1-b:
Representative Feynman diagrams of a VBS process contributing to the EW-induced production of events containing W$^\pm$W$^\pm$ (left) and WZ (right) boson pairs decaying to leptons, and two forward jets. |
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Figure 2:
Projected distributions of $ {m_{{\mathrm {j}} {\mathrm {j}}}} $ (left) and $ {p_{\mathrm {T}}} ^{{\mathrm {j}}}$ (right) in the W$^\pm$W$^\pm$ (upper) and WZ (lower) SRs. The contribution of the QCD W$^\pm$W$^\pm$ process is included together with the EW W$^\pm$W$^\pm$ process. The histograms for $ {\mathrm {t}{\mathrm{V}} \mathrm {x}} $ backgrounds include the contributions from ${\mathrm{t} {}\mathrm{\bar{t}}} {\mathrm{V}} $ and $ {\mathrm {t}\mathrm{Z} \mathrm{q}} $ processes. The histograms for other backgrounds include the contributions from double parton scattering and ${\mathrm{V}} {\mathrm{V}} {\mathrm{V}} $ processes. The histograms for wrong-sign background include the contributions from oppositely charged dilepton final states from ${\mathrm{t} {}\mathrm{\bar{t}}} $, $\mathrm{t} \mathrm{W} $, $\mathrm{W} ^{+}\mathrm{W} ^{-}$, and Drell-Yan processes. The overflow is included in the last bin. The gray bands represent the uncertainties in the predicted yields. |
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Figure 2-a:
Projected distributions of $ {m_{{\mathrm {j}} {\mathrm {j}}}} $ (left) and $ {p_{\mathrm {T}}} ^{{\mathrm {j}}}$ (right) in the W$^\pm$W$^\pm$ (upper) and WZ (lower) SRs. The contribution of the QCD W$^\pm$W$^\pm$ process is included together with the EW W$^\pm$W$^\pm$ process. The histograms for $ {\mathrm {t}{\mathrm{V}} \mathrm {x}} $ backgrounds include the contributions from ${\mathrm{t} {}\mathrm{\bar{t}}} {\mathrm{V}} $ and $ {\mathrm {t}\mathrm{Z} \mathrm{q}} $ processes. The histograms for other backgrounds include the contributions from double parton scattering and ${\mathrm{V}} {\mathrm{V}} {\mathrm{V}} $ processes. The histograms for wrong-sign background include the contributions from oppositely charged dilepton final states from ${\mathrm{t} {}\mathrm{\bar{t}}} $, $\mathrm{t} \mathrm{W} $, $\mathrm{W} ^{+}\mathrm{W} ^{-}$, and Drell-Yan processes. The overflow is included in the last bin. The gray bands represent the uncertainties in the predicted yields. |
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Figure 2-b:
Projected distributions of $ {m_{{\mathrm {j}} {\mathrm {j}}}} $ (left) and $ {p_{\mathrm {T}}} ^{{\mathrm {j}}}$ (right) in the W$^\pm$W$^\pm$ (upper) and WZ (lower) SRs. The contribution of the QCD W$^\pm$W$^\pm$ process is included together with the EW W$^\pm$W$^\pm$ process. The histograms for $ {\mathrm {t}{\mathrm{V}} \mathrm {x}} $ backgrounds include the contributions from ${\mathrm{t} {}\mathrm{\bar{t}}} {\mathrm{V}} $ and $ {\mathrm {t}\mathrm{Z} \mathrm{q}} $ processes. The histograms for other backgrounds include the contributions from double parton scattering and ${\mathrm{V}} {\mathrm{V}} {\mathrm{V}} $ processes. The histograms for wrong-sign background include the contributions from oppositely charged dilepton final states from ${\mathrm{t} {}\mathrm{\bar{t}}} $, $\mathrm{t} \mathrm{W} $, $\mathrm{W} ^{+}\mathrm{W} ^{-}$, and Drell-Yan processes. The overflow is included in the last bin. The gray bands represent the uncertainties in the predicted yields. |
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Figure 2-c:
Projected distributions of $ {m_{{\mathrm {j}} {\mathrm {j}}}} $ (left) and $ {p_{\mathrm {T}}} ^{{\mathrm {j}}}$ (right) in the W$^\pm$W$^\pm$ (upper) and WZ (lower) SRs. The contribution of the QCD W$^\pm$W$^\pm$ process is included together with the EW W$^\pm$W$^\pm$ process. The histograms for $ {\mathrm {t}{\mathrm{V}} \mathrm {x}} $ backgrounds include the contributions from ${\mathrm{t} {}\mathrm{\bar{t}}} {\mathrm{V}} $ and $ {\mathrm {t}\mathrm{Z} \mathrm{q}} $ processes. The histograms for other backgrounds include the contributions from double parton scattering and ${\mathrm{V}} {\mathrm{V}} {\mathrm{V}} $ processes. The histograms for wrong-sign background include the contributions from oppositely charged dilepton final states from ${\mathrm{t} {}\mathrm{\bar{t}}} $, $\mathrm{t} \mathrm{W} $, $\mathrm{W} ^{+}\mathrm{W} ^{-}$, and Drell-Yan processes. The overflow is included in the last bin. The gray bands represent the uncertainties in the predicted yields. |
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Figure 2-d:
Projected distributions of $ {m_{{\mathrm {j}} {\mathrm {j}}}} $ (left) and $ {p_{\mathrm {T}}} ^{{\mathrm {j}}}$ (right) in the W$^\pm$W$^\pm$ (upper) and WZ (lower) SRs. The contribution of the QCD W$^\pm$W$^\pm$ process is included together with the EW W$^\pm$W$^\pm$ process. The histograms for $ {\mathrm {t}{\mathrm{V}} \mathrm {x}} $ backgrounds include the contributions from ${\mathrm{t} {}\mathrm{\bar{t}}} {\mathrm{V}} $ and $ {\mathrm {t}\mathrm{Z} \mathrm{q}} $ processes. The histograms for other backgrounds include the contributions from double parton scattering and ${\mathrm{V}} {\mathrm{V}} {\mathrm{V}} $ processes. The histograms for wrong-sign background include the contributions from oppositely charged dilepton final states from ${\mathrm{t} {}\mathrm{\bar{t}}} $, $\mathrm{t} \mathrm{W} $, $\mathrm{W} ^{+}\mathrm{W} ^{-}$, and Drell-Yan processes. The overflow is included in the last bin. The gray bands represent the uncertainties in the predicted yields. |
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Figure 3:
Projected estimated uncertainty in the EW W$^\pm$W$^\pm$, EW WZ, and QCD WZ cross section measurements as a function of the integrated luminosity. |
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Figure 4:
Projected estimated significance for the EW $ {\mathrm{W} ^\pm _{\mathrm {L}}\mathrm{W} ^\pm _{\mathrm {L}}} $ process as a function of the integrated luminosity for the W$^\pm$W$^\pm$ and parton-parton center-of-mass reference frames. |
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Figure 5:
Projected estimated uncertainties for the EW $ {\mathrm{W} ^\pm _{\mathrm {L}}\mathrm{W} ^\pm _{\mathrm {L}}} $ (left) and EW $ {\mathrm{W} ^\pm _{\mathrm {X}}\mathrm{W} ^\pm _{\mathrm {T}}} $ (right) production cross section ratio measurements as a function of the integrated luminosity for the W$^\pm$W$^\pm$ and parton-parton center-of-mass reference frames. |
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Figure 5-a:
Projected estimated uncertainties for the EW $ {\mathrm{W} ^\pm _{\mathrm {L}}\mathrm{W} ^\pm _{\mathrm {L}}} $ (left) and EW $ {\mathrm{W} ^\pm _{\mathrm {X}}\mathrm{W} ^\pm _{\mathrm {T}}} $ (right) production cross section ratio measurements as a function of the integrated luminosity for the W$^\pm$W$^\pm$ and parton-parton center-of-mass reference frames. |
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Figure 5-b:
Projected estimated uncertainties for the EW $ {\mathrm{W} ^\pm _{\mathrm {L}}\mathrm{W} ^\pm _{\mathrm {L}}} $ (left) and EW $ {\mathrm{W} ^\pm _{\mathrm {X}}\mathrm{W} ^\pm _{\mathrm {T}}} $ (right) production cross section ratio measurements as a function of the integrated luminosity for the W$^\pm$W$^\pm$ and parton-parton center-of-mass reference frames. |
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Figure 6:
Projected estimated uncertainties for the EW $ {\mathrm{W} ^\pm _{\mathrm {L}}\mathrm{W} ^\pm _{\mathrm {L}}} $ (upper left), EW $ {\mathrm{W} ^\pm _{\mathrm {L}}\mathrm{W} ^\pm _{\mathrm {T}}} $ (upper right), and EW $ {\mathrm{W} ^\pm _{\mathrm {T}}\mathrm{W} ^\pm _{\mathrm {T}}} $ (lower) production cross section ratio measurements as a function of the integrated luminosity for the W$^\pm$W$^\pm$ and parton-parton center-of-mass reference frames. |
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Figure 6-a:
Projected estimated uncertainties for the EW $ {\mathrm{W} ^\pm _{\mathrm {L}}\mathrm{W} ^\pm _{\mathrm {L}}} $ (upper left), EW $ {\mathrm{W} ^\pm _{\mathrm {L}}\mathrm{W} ^\pm _{\mathrm {T}}} $ (upper right), and EW $ {\mathrm{W} ^\pm _{\mathrm {T}}\mathrm{W} ^\pm _{\mathrm {T}}} $ (lower) production cross section ratio measurements as a function of the integrated luminosity for the W$^\pm$W$^\pm$ and parton-parton center-of-mass reference frames. |
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Figure 6-b:
Projected estimated uncertainties for the EW $ {\mathrm{W} ^\pm _{\mathrm {L}}\mathrm{W} ^\pm _{\mathrm {L}}} $ (upper left), EW $ {\mathrm{W} ^\pm _{\mathrm {L}}\mathrm{W} ^\pm _{\mathrm {T}}} $ (upper right), and EW $ {\mathrm{W} ^\pm _{\mathrm {T}}\mathrm{W} ^\pm _{\mathrm {T}}} $ (lower) production cross section ratio measurements as a function of the integrated luminosity for the W$^\pm$W$^\pm$ and parton-parton center-of-mass reference frames. |
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Figure 6-c:
Projected estimated uncertainties for the EW $ {\mathrm{W} ^\pm _{\mathrm {L}}\mathrm{W} ^\pm _{\mathrm {L}}} $ (upper left), EW $ {\mathrm{W} ^\pm _{\mathrm {L}}\mathrm{W} ^\pm _{\mathrm {T}}} $ (upper right), and EW $ {\mathrm{W} ^\pm _{\mathrm {T}}\mathrm{W} ^\pm _{\mathrm {T}}} $ (lower) production cross section ratio measurements as a function of the integrated luminosity for the W$^\pm$W$^\pm$ and parton-parton center-of-mass reference frames. |
| Tables | |
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Table 1:
Fractions of the $ {\mathrm{W} ^\pm _{\mathrm {L}}\mathrm{W} ^\pm _{\mathrm {L}}} $, $ {\mathrm{W} ^\pm _{\mathrm {L}}\mathrm{W} ^\pm _{\mathrm {T}}} $, and $ {\mathrm{W} ^\pm _{\mathrm {T}}\mathrm{W} ^\pm _{\mathrm {T}}} $ processes, defined in W$^\pm$W$^\pm$ center-of-mass and parton-parton center-of-mass reference frames. |
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Table 2:
Selection to define the W$^\pm$W$^\pm$ and WZ SRs. The looser lepton $ {p_{\mathrm {T}}} $ requirement on the WZ selection refers to the trailing lepton from the $\mathrm{Z} $ boson decays. The $ {| {\mathrm {m}_{\ell \ell}} - {\mathrm {m}_{\mathrm{Z}}} |}$ requirement is applied to the dielectron final state only in the W$^\pm$W$^\pm$ SR. |
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Table 3:
Selection to define the nonprompt, $ {\mathrm{W} \mathrm{Z}} \mathrm{b} $, and $\mathrm{Z} \mathrm{Z} $ CRs. The looser lepton $ {p_{\mathrm {T}}} $ requirement on the $ {\mathrm{W} \mathrm{Z}} b$ CR selection refers to the trailing lepton from the $\mathrm{Z} $ boson decays. The $ {| {\mathrm {m}_{\ell \ell}} - {\mathrm {m}_{\mathrm{Z}}} |}$ requirement is applied to the dielectron final state only in the nonprompt CR. The lepton $ {p_{\mathrm {T}}} $ requirements in the $\mathrm{Z} \mathrm{Z} $ CR are ordered by the $ {p_{\mathrm {T}}} $ values themselves. |
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Table 4:
Expected yields for SM processes in W$^\pm$W$^\pm$ and WZ SRs for an integrated luminosity of 3000 fb$^{-1}$. The combination of the statistical and systematic uncertainties is shown. |
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Table 5:
Projected systematic uncertainties (in%) of the EW W$^\pm$W$^\pm$, EW WZ, and QCD WZ cross section measurements with an integrated luminosity of 3000 fb$^{-1}$. |
| Summary |
| Prospects for measuring the W$^\pm$W$^\pm$ and WZ electroweak vector boson scattering processes have been presented. The measurements are performed in the leptonic decay modes ${\mathrm{W}^\pm\mathrm{W}^\pm} \to \ell^\pm\nu\ell'^\pm\nu$ and ${\mathrm{W}\mathrm{Z}} \to \ell\nu\ell'\ell'$, where $\ell, \ell' = $ e, $\mu$. The sensitivity in the VBS cross section measurements and in the measurement of the longitudinally polarized W$^\pm$W$^\pm$ scattering were reported as a function of the integrated luminosity. The analyses were based on existing measurements at $\sqrt{s} = $ 13 TeV, that are extrapolated to the full integrated luminosity at the High-Luminosity LHC at $\sqrt{s} = $ 14 TeV, with the assumption that the signal-to-background ratio will be similar in future analyses. The projected uncertainties in the VBS cross section measurements are consistent with previous studies. The projections in the measurements of the longitudinally polarized W-boson pairs scattering are better than previous extrapolations, because of the use of more sophisticated techniques to discriminate between signal and backgrounds. The projected uncertainties with these 2-parameter fits for the ${\mathrm{W}^\pm_{\mathrm{L}}\mathrm{W}^\pm_{\mathrm{X}}} L$ components are of the order of 20-30% with an integrated luminosity of 3000 fb$^{-1}$. An extension to the existing analyses is performed by simultaneously measuring all three ${\mathrm{W}^\pm_{\mathrm{L}}\mathrm{W}^\pm_{\mathrm{X}}} L$, ${\mathrm{W}^\pm_{\mathrm{L}}\mathrm{W}^\pm_{\mathrm{X}}} T$, and ${\mathrm{W}^\pm_{\mathrm{T}}\mathrm{W}^\pm_{\mathrm{T}}} $ components. The projected uncertainties with these 3-parameter fits for the ${\mathrm{W}^\pm_{\mathrm{L}}\mathrm{W}^\pm_{\mathrm{X}}} L$ components are of the order of 30-40% with an integrated luminosity of 3000 fb$^{-1}$. |
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