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CMS-EXO-16-037 ; CERN-EP-2017-031
Search for dark matter produced with an energetic jet or a hadronically decaying W or Z boson at $ \sqrt{s} = $ 13 TeV
JHEP 07 (2017) 014
Abstract: A search for dark matter particles is performed using events with large missing transverse momentum, at least one energetic jet, and no leptons, in proton-proton collisions at $ \sqrt{s} = $ 13 TeV collected with the CMS detector at the LHC. The data sample corresponds to an integrated luminosity of 12.9 fb$^{-1}$. The search includes events with jets from the hadronic decays of a W or Z boson. The data are found to be in agreement with the predicted background contributions from standard model processes. The results are presented in terms of simplified models in which dark matter particles are produced through interactions involving a vector, axial-vector, scalar, or pseudoscalar mediator. Vector and axial-vector mediator particles with masses up to 1.95 TeV, and scalar and pseudoscalar mediator particles with masses up to 100 and 430 GeV respectively, are excluded at 95% confidence level. The results are also interpreted in terms of the invisible decays of the Higgs boson, yielding an observed (expected) 95% confidence level upper limit of 0.44 (0.56) on the corresponding branching fraction. The results of this search provide the strongest constraints on the dark matter pair production cross section through vector and axial-vector mediators at a particle collider. When compared to the direct detection experiments, the limits obtained from this search provide stronger constraints for dark matter masses less than 5, 9, and 550 GeV, assuming vector, scalar, and axial-vector mediators, respectively. The search yields stronger constraints for dark matter masses less than 200 GeV, assuming a pseudoscalar mediator, when compared to the indirect detection results from Fermi-LAT.
Figures & Tables Summary References CMS Publications
Figures

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Figure 1:
Leading order Feynman diagrams of monojet (left) and mono-V (right) production and decay of a spin-1 mediator.

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Figure 1-a:
Leading order Feynman diagram of monojet production and decay of a spin-1 mediator.

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Figure 1-b:
Leading order Feynman diagram of mono-V production and decay of a spin-1 mediator.

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Figure 2:
Leading order Feynman diagrams of monojet (left) and mono-V (right) production and decay of a spin-0 mediator.

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Figure 2-a:
Leading order Feynman diagram of monojet production and decay of a spin-0 mediator.

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Figure 2-b:
Leading order Feynman diagram of mono-V production and decay of a spin-0 mediator.

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Figure 3:
Comparison between data and Monte Carlo simulation in the $\gamma$+jets control sample before and after performing the simultaneous fit across all the control samples and the signal region, assuming the absence of any signal. The left plot shows the monojet category and the right plot shows the mono-V category. The hadronic recoil $ {p_{\mathrm {T}}} $ in $\gamma$+jets events is used as a proxy for $ {E_{\mathrm {T}}^{\text {miss}}} $ in the signal region. The filled histogram indicates the multijet background. Ratios of data and the pre-fit background prediction (red points) and post-fit background prediction (blue points) are shown for both the monojet and mono-V signal categories. The gray band indicates the overall post-fit uncertainty. The last bin includes all events with hadronic recoil $ {p_{\mathrm {T}}} $ larger than 1160 (750) GeV in the monojet (mono-V) category.

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Figure 3-a:
Comparison between data and Monte Carlo simulation in the $\gamma$+jets control sample before and after performing the simultaneous fit across all the control samples and the signal region, assuming the absence of any signal. The plot shows the monojet category. The hadronic recoil $ {p_{\mathrm {T}}} $ in $\gamma$+jets events is used as a proxy for $ {E_{\mathrm {T}}^{\text {miss}}} $ in the signal region. The filled histogram indicates the multijet background. Ratios of data and the pre-fit background prediction (red points) and post-fit background prediction (blue points) are shown. The gray band indicates the overall post-fit uncertainty. The last bin includes all events with hadronic recoil $ {p_{\mathrm {T}}} $ larger than 1160 GeV in the monojet category.

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Figure 3-b:
Comparison between data and Monte Carlo simulation in the $\gamma$+jets control sample before and after performing the simultaneous fit across all the control samples and the signal region, assuming the absence of any signal. The plot shows the mono-V category. The hadronic recoil $ {p_{\mathrm {T}}} $ in $\gamma$+jets events is used as a proxy for $ {E_{\mathrm {T}}^{\text {miss}}} $ in the signal region. The filled histogram indicates the multijet background. Ratios of data and the pre-fit background prediction (red points) and post-fit background prediction (blue points) are shown. The gray band indicates the overall post-fit uncertainty. The last bin includes all events with hadronic recoil $ {p_{\mathrm {T}}} $ larger than 750 GeV in the mono-V category.

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Figure 4:
Comparison between data and Monte Carlo simulation in the dilepton control samples before and after performing the simultaneous fit across all the control samples and the signal region, assuming the absence of any signal. Plots on the upper left and right correspond to the monojet and mono-V categories, respectively, in the dimuon control sample. Plots on the bottom left and right correspond to the monojet and mono-V categories, respectively, in the dielectron control sample. The hadronic recoil $ {p_{\mathrm {T}}} $ in dilepton events is used as a proxy for $ {E_{\mathrm {T}}^{\text {miss}}} $ in the signal region. The filled histogram indicates all processes other than ${\mathrm {Z}(\ell ^{+} \ell ^{-})}$+jets. Ratios of data and the pre-fit background prediction (red points) and post-fit background prediction (blue points) are shown for both the monojet and mono-V signal categories. The gray band indicates the overall post-fit uncertainty. The last bin includes all events with hadronic recoil $ {p_{\mathrm {T}}} $ larger than 1160 (750) GeV in the monojet (mono-V) category.

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Figure 4-a:
Comparison between data and Monte Carlo simulation in the dilepton control samples before and after performing the simultaneous fit across all the control samples and the signal region, assuming the absence of any signal. The plot corresponds to the monojet category, in the dimuon control sample. The hadronic recoil $ {p_{\mathrm {T}}} $ in dilepton events is used as a proxy for $ {E_{\mathrm {T}}^{\text {miss}}} $ in the signal region. The filled histogram indicates all processes other than ${\mathrm {Z}(\ell ^{+} \ell ^{-})}$+jets. Ratios of data and the pre-fit background prediction (red points) and post-fit background prediction (blue points) are shown for both the monojet and mono-V signal categories. The gray band indicates the overall post-fit uncertainty. The last bin includes all events with hadronic recoil $ {p_{\mathrm {T}}} $ larger than 1160 GeV in the monojet category.

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Figure 4-b:
Comparison between data and Monte Carlo simulation in the dilepton control samples before and after performing the simultaneous fit across all the control samples and the signal region, assuming the absence of any signal. The plot corresponds to the mono-V category, in the dielectron control sample. The hadronic recoil $ {p_{\mathrm {T}}} $ in dilepton events is used as a proxy for $ {E_{\mathrm {T}}^{\text {miss}}} $ in the signal region. The filled histogram indicates all processes other than ${\mathrm {Z}(\ell ^{+} \ell ^{-})}$+jets. Ratios of data and the pre-fit background prediction (red points) and post-fit background prediction (blue points) are shown for both the monojet and mono-V signal categories. The gray band indicates the overall post-fit uncertainty. The last bin includes all events with hadronic recoil $ {p_{\mathrm {T}}} $ larger than 750 GeV in the mono-V category.

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Figure 4-c:
Comparison between data and Monte Carlo simulation in the dilepton control samples before and after performing the simultaneous fit across all the control samples and the signal region, assuming the absence of any signal. The plot corresponds to the monojet category, in the dimuon control sample. The hadronic recoil $ {p_{\mathrm {T}}} $ in dilepton events is used as a proxy for $ {E_{\mathrm {T}}^{\text {miss}}} $ in the signal region. The filled histogram indicates all processes other than ${\mathrm {Z}(\ell ^{+} \ell ^{-})}$+jets. Ratios of data and the pre-fit background prediction (red points) and post-fit background prediction (blue points) are shown for both the monojet and mono-V signal categories. The gray band indicates the overall post-fit uncertainty. The last bin includes all events with hadronic recoil $ {p_{\mathrm {T}}} $ larger than 1160 GeV in the monojet category.

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Figure 4-d:
Comparison between data and Monte Carlo simulation in the dilepton control samples before and after performing the simultaneous fit across all the control samples and the signal region, assuming the absence of any signal. The plot corresponds to the mono-V category, in the dielectron control sample. The hadronic recoil $ {p_{\mathrm {T}}} $ in dilepton events is used as a proxy for $ {E_{\mathrm {T}}^{\text {miss}}} $ in the signal region. The filled histogram indicates all processes other than ${\mathrm {Z}(\ell ^{+} \ell ^{-})}$+jets. Ratios of data and the pre-fit background prediction (red points) and post-fit background prediction (blue points) are shown for both the monojet and mono-V signal categories. The gray band indicates the overall post-fit uncertainty. The last bin includes all events with hadronic recoil $ {p_{\mathrm {T}}} $ larger than 750 GeV in the mono-V category.

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Figure 5:
Comparison between data and Monte Carlo simulation in the single-lepton control samples before and after performing the simultaneous fit across all the control samples and the signal region, assuming the absence of any signal. Plots on the upper left and right correspond to the monojet and mono-V categories, respectively, in the single-muon control sample. Plots on the bottom left and right correspond to the monojet and mono-V categories, respectively, in the single-electron control sample. The hadronic recoil $ {p_{\mathrm {T}}} $ in single-lepton events is used as a proxy for $ {E_{\mathrm {T}}^{\text {miss}}} $ in the signal region. The filled histogram indicates all processes other than ${\mathrm {W}(\ell \nu )}$+jets. Ratios of data and the pre-fit background prediction (red points) and post-fit background prediction (blue points) are shown for both the monojet and mono-V signal categories. The gray band indicates the overall post-fit uncertainty. The last bin includes all events with hadronic recoil $ {p_{\mathrm {T}}} $ larger than 1160 (750) GeV in the monojet (mono-V) category.

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Figure 5-a:
Comparison between data and Monte Carlo simulation in the single-lepton control samples before and after performing the simultaneous fit across all the control samples and the signal region, assuming the absence of any signal. The plot corresponds to the monojet category, in the single-muon control sample. The hadronic recoil $ {p_{\mathrm {T}}} $ in single-lepton events is used as a proxy for $ {E_{\mathrm {T}}^{\text {miss}}} $ in the signal region. The filled histogram indicates all processes other than ${\mathrm {W}(\ell \nu )}$+jets. Ratios of data and the pre-fit background prediction (red points) and post-fit background prediction (blue points) are shown for both the monojet and mono-V signal categories. The gray band indicates the overall post-fit uncertainty. The last bin includes all events with hadronic recoil $ {p_{\mathrm {T}}} $ larger than 1160 GeV in the monojet category.

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Figure 5-b:
Comparison between data and Monte Carlo simulation in the single-lepton control samples before and after performing the simultaneous fit across all the control samples and the signal region, assuming the absence of any signal. The plot corresponds to the mono-V category, in the single-electron control sample. The hadronic recoil $ {p_{\mathrm {T}}} $ in single-lepton events is used as a proxy for $ {E_{\mathrm {T}}^{\text {miss}}} $ in the signal region. The filled histogram indicates all processes other than ${\mathrm {W}(\ell \nu )}$+jets. Ratios of data and the pre-fit background prediction (red points) and post-fit background prediction (blue points) are shown for both the monojet and mono-V signal categories. The gray band indicates the overall post-fit uncertainty. The last bin includes all events with hadronic recoil $ {p_{\mathrm {T}}} $ larger than 750 GeV in the mono-V category.

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Figure 5-c:
Comparison between data and Monte Carlo simulation in the single-lepton control samples before and after performing the simultaneous fit across all the control samples and the signal region, assuming the absence of any signal. The plot corresponds to the monojet category, in the single-muon control sample. The hadronic recoil $ {p_{\mathrm {T}}} $ in single-lepton events is used as a proxy for $ {E_{\mathrm {T}}^{\text {miss}}} $ in the signal region. The filled histogram indicates all processes other than ${\mathrm {W}(\ell \nu )}$+jets. Ratios of data and the pre-fit background prediction (red points) and post-fit background prediction (blue points) are shown for both the monojet and mono-V signal categories. The gray band indicates the overall post-fit uncertainty. The last bin includes all events with hadronic recoil $ {p_{\mathrm {T}}} $ larger than 1160 GeV in the monojet category.

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Figure 5-d:
Comparison between data and Monte Carlo simulation in the single-lepton control samples before and after performing the simultaneous fit across all the control samples and the signal region, assuming the absence of any signal. The plot corresponds to the mono-V category, in the single-electron control sample. The hadronic recoil $ {p_{\mathrm {T}}} $ in single-lepton events is used as a proxy for $ {E_{\mathrm {T}}^{\text {miss}}} $ in the signal region. The filled histogram indicates all processes other than ${\mathrm {W}(\ell \nu )}$+jets. Ratios of data and the pre-fit background prediction (red points) and post-fit background prediction (blue points) are shown for both the monojet and mono-V signal categories. The gray band indicates the overall post-fit uncertainty. The last bin includes all events with hadronic recoil $ {p_{\mathrm {T}}} $ larger than 750 GeV in the mono-V category.

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Figure 6:
Observed $ {E_{\mathrm {T}}^{\text {miss}}} $ distribution in the monojet (left) and mono-V (right) signal regions compared with the background expectations for various SM processes evaluated after performing a combined fit to the data in all the control samples, but excluding the signal region. The last bin includes all events with $ {E_{\mathrm {T}}^{\text {miss}}} > $ 1160 (750) GeV for the monojet (mono-V) category. Expected signal distributions for a 125 GeV Higgs boson decaying exclusively to invisible particles, and for a 1.6 TeV axial-vector mediator decaying to 1 GeV DM particles, are overlaid. The ratio of data and the post-fit background prediction is shown for both the monojet and mono-V signal regions. The gray bands in these ratio plots indicate the post-fit uncertainty in the background prediction. Finally, the distributions of the pulls, defined as the difference between data and the post-fit background prediction relative to the post-fit uncertainty in the prediction, are also shown in the lower panels.

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Figure 6-a:
Observed $ {E_{\mathrm {T}}^{\text {miss}}} $ distribution in the monojet signal regions compared with the background expectations for various SM processes evaluated after performing a combined fit to the data in all the control samples, but excluding the signal region. The last bin includes all events with $ {E_{\mathrm {T}}^{\text {miss}}} > $ 1160 GeV for the monojet category. Expected signal distributions for a 125 GeV Higgs boson decaying exclusively to invisible particles, and for a 1.6 TeV axial-vector mediator decaying to 1 GeV DM particles, are overlaid. The ratio of data and the post-fit background prediction is shown. The gray bands in these ratio plots indicate the post-fit uncertainty in the background prediction. Finally, the distributions of the pulls, defined as the difference between data and the post-fit background prediction relative to the post-fit uncertainty in the prediction, are also shown in the lower panels.

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Figure 6-b:
Observed $ {E_{\mathrm {T}}^{\text {miss}}} $ distribution in the mono-V signal regions compared with the background expectations for various SM processes evaluated after performing a combined fit to the data in all the control samples, but excluding the signal region. The last bin includes all events with $ {E_{\mathrm {T}}^{\text {miss}}} > $ 750 GeV for the mono-V category. Expected signal distributions for a 125 GeV Higgs boson decaying exclusively to invisible particles, and for a 1.6 TeV axial-vector mediator decaying to 1 GeV DM particles, are overlaid. The ratio of data and the post-fit background prediction is shown. The gray bands in these ratio plots indicate the post-fit uncertainty in the background prediction. Finally, the distributions of the pulls, defined as the difference between data and the post-fit background prediction relative to the post-fit uncertainty in the prediction, are also shown in the lower panels.

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Figure 7:
Observed $ {E_{\mathrm {T}}^{\text {miss}}} $ distribution in the monojet (left) and mono-V (right) signal regions compared with the background expectations for various SM processes evaluated after performing a combined fit to the data in all the control samples, as well as in the signal region. The fit is performed assuming the absence of any signal. The last bin includes all events with $ {E_{\mathrm {T}}^{\text {miss}}} > $ 1160 (750) GeV for the monojet (mono-V) category. Expected signal distributions for a 125 GeV Higgs boson decaying exclusively to invisible particles, and for a 1.6 TeV axial-vector mediator decaying to 1 GeV DM particles, are overlaid. The ratio of data and the post-fit background prediction is shown for both the monojet and mono-V signal regions. The gray bands in these ratio plots indicate the post-fit uncertainty in the background prediction. Finally, the distributions of the pulls, defined as the difference between data and the post-fit background prediction relative to the post-fit uncertainty in the prediction, are also shown in the lower panels.

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Figure 7-a:
Observed $ {E_{\mathrm {T}}^{\text {miss}}} $ distribution in the monojet signal regions compared with the background expectations for various SM processes evaluated after performing a combined fit to the data in all the control samples, as well as in the signal region. The fit is performed assuming the absence of any signal. The last bin includes all events with $ {E_{\mathrm {T}}^{\text {miss}}} > $ 1160 GeV for the monojet category. Expected signal distributions for a 125 GeV Higgs boson decaying exclusively to invisible particles, and for a 1.6 TeV axial-vector mediator decaying to 1 GeV DM particles, are overlaid. The ratio of data and the post-fit background prediction is shown for both the monojet and mono-V signal regions. The gray bands in these ratio plots indicate the post-fit uncertainty in the background prediction. Finally, the distributions of the pulls, defined as the difference between data and the post-fit background prediction relative to the post-fit uncertainty in the prediction, are also shown in the lower panels.

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Figure 7-b:
Observed $ {E_{\mathrm {T}}^{\text {miss}}} $ distribution in the mono-V signal regions compared with the background expectations for various SM processes evaluated after performing a combined fit to the data in all the control samples, as well as in the signal region. The fit is performed assuming the absence of any signal. The last bin includes all events with $ {E_{\mathrm {T}}^{\text {miss}}} > $ 750 GeV for the mono-V category. Expected signal distributions for a 125 GeV Higgs boson decaying exclusively to invisible particles, and for a 1.6 TeV axial-vector mediator decaying to 1 GeV DM particles, are overlaid. The ratio of data and the post-fit background prediction is shown for both the monojet and mono-V signal regions. The gray bands in these ratio plots indicate the post-fit uncertainty in the background prediction. Finally, the distributions of the pulls, defined as the difference between data and the post-fit background prediction relative to the post-fit uncertainty in the prediction, are also shown in the lower panels.

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Figure 8:
Exclusion limits at 95% CL on the signal strength $\mu =\sigma /\sigma _{\textrm {th}}$ in the $m_{\textrm {med}}$-$m_{\textrm {DM}}$ plane assuming vector (left) and axial-vector (right) mediators. The limits are shown for $m_{\textrm {med}}$ between 150 GeV and 2.5 TeV, and $m_{\textrm {DM}}$ between 50 GeV and 1.2 TeV. While the excluded area is expected to extend below these minimum values of $m_{\textrm {med}}$ and $m_{\textrm {DM}}$, the axes do not extend below these values as the signal simulation was not performed in this region. The solid (dotted) red (blue) line shows the contour for the observed (expected) exclusion. The solid contours around the observed limit and the dashed contours around the expected limit represent one standard deviation theoretical uncertainties in the signal cross section and the combination of the statistical and experimental systematic uncertainties, respectively. Constraints from the Planck satellite experiment [83] are shown with the dark green contours and associated hatching. The hatched area indicates the region where the DM density exceeds the observed value.

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Figure 8-a:
Exclusion limits at 95% CL on the signal strength $\mu =\sigma /\sigma _{\textrm {th}}$ in the $m_{\textrm {med}}$-$m_{\textrm {DM}}$ plane assuming vector mediators. The limits are shown for $m_{\textrm {med}}$ between 150 GeV and 2.5 TeV, and $m_{\textrm {DM}}$ between 50 GeV and 1.2 TeV. While the excluded area is expected to extend below these minimum values of $m_{\textrm {med}}$ and $m_{\textrm {DM}}$, the axes do not extend below these values as the signal simulation was not performed in this region. The solid (dotted) red (blue) line shows the contour for the observed (expected) exclusion. The solid contours around the observed limit and the dashed contours around the expected limit represent one standard deviation theoretical uncertainties in the signal cross section and the combination of the statistical and experimental systematic uncertainties, respectively. Constraints from the Planck satellite experiment [83] are shown with the dark green contours and associated hatching. The hatched area indicates the region where the DM density exceeds the observed value.

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Figure 8-b:
Exclusion limits at 95% CL on the signal strength $\mu =\sigma /\sigma _{\textrm {th}}$ in the $m_{\textrm {med}}$-$m_{\textrm {DM}}$ plane assuming axial-vector mediators. The limits are shown for $m_{\textrm {med}}$ between 150 GeV and 2.5 TeV, and $m_{\textrm {DM}}$ between 50 GeV and 1.2 TeV. While the excluded area is expected to extend below these minimum values of $m_{\textrm {med}}$ and $m_{\textrm {DM}}$, the axes do not extend below these values as the signal simulation was not performed in this region. The solid (dotted) red (blue) line shows the contour for the observed (expected) exclusion. The solid contours around the observed limit and the dashed contours around the expected limit represent one standard deviation theoretical uncertainties in the signal cross section and the combination of the statistical and experimental systematic uncertainties, respectively. Constraints from the Planck satellite experiment [83] are shown with the dark green contours and associated hatching. The hatched area indicates the region where the DM density exceeds the observed value.

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Figure 9:
Exclusion limits at 95% CL on signal strength the $\mu =\sigma /\sigma _{\textrm {th}}$ in the $m_{\textrm {med}}$-$m_{\textrm {DM}}$ plane assuming scalar (left) and pseudoscalar (right) mediators. The limits are shown for $m_{\textrm {med}}$ between 50 and 500 GeV, and $m_{\textrm {DM}}$ between 0 and 300 GeV. While the excluded area is expected to extend below the minimum value of $m_{\textrm {med}}$, the axis does not extend below this value as the signal simulation was not performed in this region. The red line shows the contour for the observed exclusion. The solid red contours around the observed limit represent one standard deviation theoretical uncertainties in the signal cross section. The dashed blue contour in the case of the scalar mediator shows the $-1\sigma $ deviation due to the combination of the statistical and experimental systematic uncertainties. Constraints from the Planck satellite experiment [83] are shown with the dark green contours and associated hatching. The hatched area indicates the region where the DM density exceeds the observed value.

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Figure 9-a:
Exclusion limits at 95% CL on signal strength the $\mu =\sigma /\sigma _{\textrm {th}}$ in the $m_{\textrm {med}}$-$m_{\textrm {DM}}$ plane assuming scalar mediators. The limits are shown for $m_{\textrm {med}}$ between 50 and 500 GeV, and $m_{\textrm {DM}}$ between 0 and 300 GeV. While the excluded area is expected to extend below the minimum value of $m_{\textrm {med}}$, the axis does not extend below this value as the signal simulation was not performed in this region. The red line shows the contour for the observed exclusion. The solid red contours around the observed limit represent one standard deviation theoretical uncertainties in the signal cross section. The dashed blue contour in the case of the scalar mediator shows the $-1\sigma $ deviation due to the combination of the statistical and experimental systematic uncertainties. Constraints from the Planck satellite experiment [83] are shown with the dark green contours and associated hatching. The hatched area indicates the region where the DM density exceeds the observed value.

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Figure 9-b:
Exclusion limits at 95% CL on signal strength the $\mu =\sigma /\sigma _{\textrm {th}}$ in the $m_{\textrm {med}}$-$m_{\textrm {DM}}$ plane assuming pseudoscalar mediators. The limits are shown for $m_{\textrm {med}}$ between 50 and 500 GeV, and $m_{\textrm {DM}}$ between 0 and 300 GeV. While the excluded area is expected to extend below the minimum value of $m_{\textrm {med}}$, the axis does not extend below this value as the signal simulation was not performed in this region. The red line shows the contour for the observed exclusion. The solid red contours around the observed limit represent one standard deviation theoretical uncertainties in the signal cross section. The dashed blue contour in the case of the scalar mediator shows the $-1\sigma $ deviation due to the combination of the statistical and experimental systematic uncertainties. Constraints from the Planck satellite experiment [83] are shown with the dark green contours and associated hatching. The hatched area indicates the region where the DM density exceeds the observed value.

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Figure 10:
Expected (dotted black line) and observed (solid black line) 95% CL upper limits on the signal strength $\mu $ as a function of the mediator mass for the spin-0 models. The horizontal red line denotes $\mu = 1$. Limits for the scalar model on the combined cross section of the monojet and mono-V processes (upper left). Limits for the scalar (upper right) and pseudoscalar (bottom) models, respectively, assuming only the monojet signal process.

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Figure 10-a:
Expected (dotted black line) and observed (solid black line) 95% CL upper limits on the signal strength $\mu $ as a function of the mediator mass for the spin-0 models. The horizontal red line denotes $\mu = 1$. Limits for the scalar model on the combined cross section of the monojet and mono-V processes.

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Figure 10-b:
Expected (dotted black line) and observed (solid black line) 95% CL upper limits on the signal strength $\mu $ as a function of the mediator mass for the spin-0 models. The horizontal red line denotes $\mu = 1$. Limit for the scalar model, assuming only the monojet signal process.

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Figure 10-c:
Expected (dotted black line) and observed (solid black line) 95% CL upper limits on the signal strength $\mu $ as a function of the mediator mass for the spin-0 models. The horizontal red line denotes $\mu = 1$. Limit for the pseudoscalar model, assuming only the monojet signal process.

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Figure 11:
Exclusion limits at 90% CL in the $m_{\textrm {DM}}$ vs. $\sigma _{\textrm {SI/SD}}$ plane for vector (left) and axial-vector (right) mediator models. The solid (dotted) red line shows the contour for the observed (expected) exclusion in this search. Limits from the CDMSLite [90], LUX [91], PandaX-II [92], and CRESST-II [93] experiments are shown for the vector mediator. Limits from the PICO-2L [94], PICO-60 [95], IceCube [96], and Super-Kamiokande [97] experiments are shown for the axial-vector mediator.

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Figure 11-a:
Exclusion limits at 90% CL in the $m_{\textrm {DM}}$ vs. $\sigma _{\textrm {SI/SD}}$ plane for the vector mediator model. The solid (dotted) red line shows the contour for the observed (expected) exclusion in this search. Limits from the CDMSLite [90], LUX [91], PandaX-II [92], and CRESST-II [93] experiments are shown.

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Figure 11-b:
Exclusion limits at 90% CL in the $m_{\textrm {DM}}$ vs. $\sigma _{\textrm {SI/SD}}$ plane for axial-vector mediator models. The solid (dotted) red line shows the contour for the observed (expected) exclusion in this search. Limits from the PICO-2L [94], PICO-60 [95], IceCube [96], and Super-Kamiokande [97] experiments are shown.

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Figure 12:
Exclusion limits at 90% CL in the $m_{\textrm {DM}}$ vs. $\sigma _{\textrm {SI/SD}}$ plane for the scalar mediator model (left). The observed exclusion in this search (red line) is compared to the results from the CDMSLite [90], LUX [91], PandaX-II [92], and CRESST-II [93] experiments. For the pseudoscalar mediator (right), limits are compared to the the velocity-averaged DM annihilation cross section upper limits from Fermi-LAT [89]. There are no comparable limits from direct detection experiments as the scattering cross section between DM particles and SM quarks is suppressed at nonrelativistic velocities for a pseudoscalar mediator [98,99].

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Figure 12-a:
Exclusion limits at 90% CL in the $m_{\textrm {DM}}$ vs. $\sigma _{\textrm {SI/SD}}$ plane for the scalar mediator model. The observed exclusion in this search (red line) is compared to the results from the CDMSLite [90], LUX [91], PandaX-II [92], and CRESST-II [93] experiments.

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Figure 12-b:
Exclusion limits at 90% CL in the $m_{\textrm {DM}}$ vs. $\sigma _{\textrm {SI/SD}}$ plane for the pseudoscalar mediator. Limits are compared to the the velocity-averaged DM annihilation cross section upper limits from Fermi-LAT [89]. There are no comparable limits from direct detection experiments as the scattering cross section between DM particles and SM quarks is suppressed at nonrelativistic velocities for a pseudoscalar mediator [98,99].

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Figure 13:
Expected (dotted black line) and observed (solid black line) 95% CL upper limits on the invisible branching fraction of a 125 GeV SM-like Higgs boson. Limits are shown for the monojet and mono-V categories separately, and also for their combination.

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Figure 14:
Correlations between the uncertainties in the estimated background yields in all the $ {E_{\mathrm {T}}^{\text {miss}}} $ bins of the monojet signal region. The boundaries of the $ {E_{\mathrm {T}}^{\text {miss}}} $ bins, expressed in GeV, are shown at the bottom and on the left.

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Figure 15:
Correlations between the uncertainties in the estimated background yields in all the $ {E_{\mathrm {T}}^{\text {miss}}} $ bins of the mono-V signal region. The boundaries of the $ {E_{\mathrm {T}}^{\text {miss}}} $ bins, expressed in GeV, are shown at the bottom and on the left.
Tables

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Table 1:
Monte Carlo generators used for simulating various signal and background processes.

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Table 2:
Selection requirements for the mono-V and monojet event categories.

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Table 3:
Expected event yields in each $ {E_{\mathrm {T}}^{\text {miss}}} $ bin for various background processes in the monojet signal region. The background yields and the corresponding uncertainties are obtained after performing a combined fit to data in all the control samples, but excluding data in the signal region. The observed event yields in the monojet signal region are also reported.

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Table 4:
Expected event yields in each $ {E_{\mathrm {T}}^{\text {miss}}} $ bin for various background processes in the mono-V signal region. The background yields and the corresponding uncertainties are obtained after performing a combined fit to data in all the control samples, excluding data in the signal region. The observed event yields in the mono-V signal region are also reported.

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Table 5:
Expected and observed 95% CL upper limits on the invisible branching fraction of the Higgs boson. Limits are tabulated for the monojet and mono-V categories separately, and for their combination. The one standard deviation uncertainty range on the expected limits is listed. The signal composition in terms of gluon fusion, vector boson fusion, and an associated production with a W or Z boson is also provided.
Summary
A search for dark matter (DM) is presented using events with jets and large missing transverse momentum in a $ \sqrt{s} = $ 13 TeV proton-proton collision data set corresponding to an integrated luminosity of 12.9 fb$^{-1}$. The search also exploits events with a hadronic decay of a W or Z boson reconstructed as a single large-radius jet. No significant excess is observed with respect to the standard model backgrounds. Limits are computed on the DM production cross section using simplified models in which DM production is mediated by spin-1 or spin-0 particles. Vector and axial-vector mediators with masses up to 1.95 TeV are excluded at 95% confidence level, assuming a coupling strength of 0.25 between the mediators and the standard model fermions, and a coupling strength of 1.0 between the mediators and the DM particles. The results of this search provide the strongest constraints on DM pair production through vector and axial-vector mediators at a particle collider. Scalar and pseudoscalar mediators with masses up to 100 and 430 GeV, respectively, are excluded at 95% confidence level, assuming the coupling of the spin-0 mediators with DM particles to be 1.0 and the coupling of the spin-0 mediators with standard model fermions to be the same as the standard model Yukawa interactions. When compared to the direct detection experiments, the limits obtained from this search provide stronger constraints for dark matter masses less than 5, 9, and 550 GeV, assuming vector, scalar, and axial-vector mediators, respectively. The search yields stronger constraints for dark matter masses less than 200 GeV, assuming a pseudoscalar mediator, when compared to the indirect detection results from Fermi-LAT. The search also yields an observed (expected) 95% confidence level upper limit of 0.44 (0.56) on the invisible branching fraction of a standard model-like 125 GeV Higgs boson, assuming the standard model production cross section.



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