Measurement of detector-corrected observables sensitive to the anomalous production of events with jets and large missing transverse momentum in $pp$ collisions at $\sqrt{s}=13$ TeV using the ATLAS detector
Observables sensitive to the anomalous production of events containing hadronic jets and missing momentum in the plane transverse to the proton beams at the Large Hadron Collider are presented. The observables are defined as a ratio of cross sections, for events containing jets and large missing transverse momentum to events containing jets and a pair of charged leptons from the decay of a $Z/\gamma^\ast$ boson. This definition minimises experimental and theoretical systematic uncertainties in the measurements. This ratio is measured differentially with respect to a number of kinematic properties of the hadronic system in two phase-space regions; one inclusive single-jet region and one region sensitive to vector-boson-fusion topologies. The data are found to be in agreement with the Standard Model predictions and used to constrain a variety of theoretical models for dark-matter production, including simplified models, effective field theory models, and invisible decays of the Higgs boson. The measurements use 3.2 fb$^{-1}$ of proton--proton collision data recorded by the ATLAS experiment at a centre-of-mass energy of 13 TeV and are fully corrected for detector effects, meaning that the data can be used to constrain new-physics models beyond those shown in this paper.
11 July 2017
Contact: Exotics conveners
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e-print arXiv:1707.03263 - pdf from arXiv - Physics Briefing
Figures
Figure 01a
Example Feynman diagrams for WIMP χ pair production with mediator A produced (a) in association with one jet and (b) via vector-boson fusion. Example Feynman diagrams for the Standard Model background to (c) the process with one jet and (d) the vector-boson fusion process.
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Figure 01b
Example Feynman diagrams for WIMP χ pair production with mediator A produced (a) in association with one jet and (b) via vector-boson fusion. Example Feynman diagrams for the Standard Model background to (c) the process with one jet and (d) the vector-boson fusion process.
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Figure 01c
Example Feynman diagrams for WIMP χ pair production with mediator A produced (a) in association with one jet and (b) via vector-boson fusion. Example Feynman diagrams for the Standard Model background to (c) the process with one jet and (d) the vector-boson fusion process.
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Figure 01d
Example Feynman diagrams for WIMP χ pair production with mediator A produced (a) in association with one jet and (b) via vector-boson fusion. Example Feynman diagrams for the Standard Model background to (c) the process with one jet and (d) the vector-boson fusion process.
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Figure 02a
Comparisons between detector-level distributions for data and MC simulation of Z → νanti-ν and Z → ℓℓ events plus predicted backgrounds in selected (a,c) pTmiss + jets events and (b,d) ℓ+ℓ- + jets events as a function of the pTmiss variable in the (a,b) ≥ 1 jet phase space and (c,d) VBF phase space. The lower panel shows the ratio of data to the Standard Model prediction. The error bars show the statistical uncertainty of the data. Uncertainties in the predictions are shown as hatched bands and include the statistical component as well as systematic contributions from theoretical predictions, lepton efficiencies and jet energy scales and resolutions to the MC predictions and uncertainties in the data-driven background estimates, explained in Section 8.
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Figure 02b
Comparisons between detector-level distributions for data and MC simulation of Z → νanti-ν and Z → ℓℓ events plus predicted backgrounds in selected (a,c) pTmiss + jets events and (b,d) ℓ+ℓ- + jets events as a function of the pTmiss variable in the (a,b) ≥ 1 jet phase space and (c,d) VBF phase space. The lower panel shows the ratio of data to the Standard Model prediction. The error bars show the statistical uncertainty of the data. Uncertainties in the predictions are shown as hatched bands and include the statistical component as well as systematic contributions from theoretical predictions, lepton efficiencies and jet energy scales and resolutions to the MC predictions and uncertainties in the data-driven background estimates, explained in Section 8.
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Figure 02c
Comparisons between detector-level distributions for data and MC simulation of Z → νanti-ν and Z → ℓℓ events plus predicted backgrounds in selected (a,c) pTmiss + jets events and (b,d) ℓ+ℓ- + jets events as a function of the pTmiss variable in the (a,b) ≥ 1 jet phase space and (c,d) VBF phase space. The lower panel shows the ratio of data to the Standard Model prediction. The error bars show the statistical uncertainty of the data. Uncertainties in the predictions are shown as hatched bands and include the statistical component as well as systematic contributions from theoretical predictions, lepton efficiencies and jet energy scales and resolutions to the MC predictions and uncertainties in the data-driven background estimates, explained in Section 8.
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Figure 02d
Comparisons between detector-level distributions for data and MC simulation of Z → νanti-ν and Z → ℓℓ events plus predicted backgrounds in selected (a,c) pTmiss + jets events and (b,d) ℓ+ℓ- + jets events as a function of the pTmiss variable in the (a,b) ≥ 1 jet phase space and (c,d) VBF phase space. The lower panel shows the ratio of data to the Standard Model prediction. The error bars show the statistical uncertainty of the data. Uncertainties in the predictions are shown as hatched bands and include the statistical component as well as systematic contributions from theoretical predictions, lepton efficiencies and jet energy scales and resolutions to the MC predictions and uncertainties in the data-driven background estimates, explained in Section 8.
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Figure 03a
Comparisons between detector-level distributions for data and MC simulation of Z → νanti-ν and Z → ℓℓ events plus predicted backgrounds in selected (a,c) pTmiss + jets events and (b,d) ℓ+ℓ- + jets events as a function of (a,b) mjj and (c,d) Δφjj in the VBF phase space. The lower panel shows the ratio of data to the Standard Model prediction. The error bars show the statistical uncertainty of the data. Uncertainties in the predictions are shown as hatched bands and include the statistical component as well as systematic contributions from theoretical predictions, lepton efficiencies and jet energy scales and resolutions to the MC predictions and uncertainties in the data-driven background estimates, explained in Section 8.
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Figure 03b
Comparisons between detector-level distributions for data and MC simulation of Z → νanti-ν and Z → ℓℓ events plus predicted backgrounds in selected (a,c) pTmiss + jets events and (b,d) ℓ+ℓ- + jets events as a function of (a,b) mjj and (c,d) Δφjj in the VBF phase space. The lower panel shows the ratio of data to the Standard Model prediction. The error bars show the statistical uncertainty of the data. Uncertainties in the predictions are shown as hatched bands and include the statistical component as well as systematic contributions from theoretical predictions, lepton efficiencies and jet energy scales and resolutions to the MC predictions and uncertainties in the data-driven background estimates, explained in Section 8.
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Figure 03c
Comparisons between detector-level distributions for data and MC simulation of Z → νanti-ν and Z → ℓℓ events plus predicted backgrounds in selected (a,c) pTmiss + jets events and (b,d) ℓ+ℓ- + jets events as a function of (a,b) mjj and (c,d) Δφjj in the VBF phase space. The lower panel shows the ratio of data to the Standard Model prediction. The error bars show the statistical uncertainty of the data. Uncertainties in the predictions are shown as hatched bands and include the statistical component as well as systematic contributions from theoretical predictions, lepton efficiencies and jet energy scales and resolutions to the MC predictions and uncertainties in the data-driven background estimates, explained in Section 8.
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Figure 03d
Comparisons between detector-level distributions for data and MC simulation of Z → νanti-ν and Z → ℓℓ events plus predicted backgrounds in selected (a,c) pTmiss + jets events and (b,d) ℓ+ℓ- + jets events as a function of (a,b) mjj and (c,d) Δφjj in the VBF phase space. The lower panel shows the ratio of data to the Standard Model prediction. The error bars show the statistical uncertainty of the data. Uncertainties in the predictions are shown as hatched bands and include the statistical component as well as systematic contributions from theoretical predictions, lepton efficiencies and jet energy scales and resolutions to the MC predictions and uncertainties in the data-driven background estimates, explained in Section 8.
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Figure 04a
Measured Rmiss as a function of (a) pTmiss in the ≥ 1 jet region, (b) pTmiss in the VBF region, (c) mjj in the VBF region and (d) Δφjj in the VBF region. Statistical uncertainties are shown as error bars and the total statistical and systematic uncertainties are shown as solid grey bands. The results are compared to the SM prediction and to SM+BSM for four BSM models. One is a simplified model of WIMP production with an s-channel exchange of an axial-vector mediator with mass of 1 TeV coupling to quarks and a WIMPs with a mass of 10 GeV, another represents the Higgs boson decaying to invisible particles with 50 % branching fraction, and another two represent the predictions of two EFT operators allowing the production of WIMP dark matter through interactions with vector bosons (with differing charge-parity properties in the interaction). The Rmiss values of the third and fourth models in the highest pTmiss bin in the ≥ 1 jet region are 18.8 and 38.3, respectively, and in the highest pTmiss bin in the VBF region the fourth model has an Rmiss value of 19.4. The red hatched error bars correspond to the uncertainty in the SM prediction. The bottom panel shows the ratio of data to the SM prediction.
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Figure 04b
Measured Rmiss as a function of (a) pTmiss in the ≥ 1 jet region, (b) pTmiss in the VBF region, (c) mjj in the VBF region and (d) Δφjj in the VBF region. Statistical uncertainties are shown as error bars and the total statistical and systematic uncertainties are shown as solid grey bands. The results are compared to the SM prediction and to SM+BSM for four BSM models. One is a simplified model of WIMP production with an s-channel exchange of an axial-vector mediator with mass of 1 TeV coupling to quarks and a WIMPs with a mass of 10 GeV, another represents the Higgs boson decaying to invisible particles with 50 % branching fraction, and another two represent the predictions of two EFT operators allowing the production of WIMP dark matter through interactions with vector bosons (with differing charge-parity properties in the interaction). The Rmiss values of the third and fourth models in the highest pTmiss bin in the ≥ 1 jet region are 18.8 and 38.3, respectively, and in the highest pTmiss bin in the VBF region the fourth model has an Rmiss value of 19.4. The red hatched error bars correspond to the uncertainty in the SM prediction. The bottom panel shows the ratio of data to the SM prediction.
png (27kB) pdf (18kB)
Figure 04c
Measured Rmiss as a function of (a) pTmiss in the ≥ 1 jet region, (b) pTmiss in the VBF region, (c) mjj in the VBF region and (d) Δφjj in the VBF region. Statistical uncertainties are shown as error bars and the total statistical and systematic uncertainties are shown as solid grey bands. The results are compared to the SM prediction and to SM+BSM for four BSM models. One is a simplified model of WIMP production with an s-channel exchange of an axial-vector mediator with mass of 1 TeV coupling to quarks and a WIMPs with a mass of 10 GeV, another represents the Higgs boson decaying to invisible particles with 50 % branching fraction, and another two represent the predictions of two EFT operators allowing the production of WIMP dark matter through interactions with vector bosons (with differing charge-parity properties in the interaction). The Rmiss values of the third and fourth models in the highest pTmiss bin in the ≥ 1 jet region are 18.8 and 38.3, respectively, and in the highest pTmiss bin in the VBF region the fourth model has an Rmiss value of 19.4. The red hatched error bars correspond to the uncertainty in the SM prediction. The bottom panel shows the ratio of data to the SM prediction.
png (28kB) pdf (19kB)
Figure 04d
Measured Rmiss as a function of (a) pTmiss in the ≥ 1 jet region, (b) pTmiss in the VBF region, (c) mjj in the VBF region and (d) Δφjj in the VBF region. Statistical uncertainties are shown as error bars and the total statistical and systematic uncertainties are shown as solid grey bands. The results are compared to the SM prediction and to SM+BSM for four BSM models. One is a simplified model of WIMP production with an s-channel exchange of an axial-vector mediator with mass of 1 TeV coupling to quarks and a WIMPs with a mass of 10 GeV, another represents the Higgs boson decaying to invisible particles with 50 % branching fraction, and another two represent the predictions of two EFT operators allowing the production of WIMP dark matter through interactions with vector bosons (with differing charge-parity properties in the interaction). The Rmiss values of the third and fourth models in the highest pTmiss bin in the ≥ 1 jet region are 18.8 and 38.3, respectively, and in the highest pTmiss bin in the VBF region the fourth model has an Rmiss value of 19.4. The red hatched error bars correspond to the uncertainty in the SM prediction. The bottom panel shows the ratio of data to the SM prediction.
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Figure 05
Exclusion contours (at 95 % CL) in the WIMP--mediator mass plane for a simplified model with an axial-vector mediator and couplings gq = 0.25 and gχ=1. The solid purple (green) curve shows the the observed (expected) limit. The yellow filled region around the expected limit indicates the effect of ± 1σ experimental uncertainties in the expected limit. The red curve corresponds to the expected relic density. The grey hatched region shows the region of non-perturbativity defined by WIMP mass greater than √π/2 times the mediator mass. Also shown, for comparison, are limits set using detector-level event counts from Ref. [4]. The exclusion is based on the global fit to the pTmiss distributions in the ≥ 1 jet and VBF phase spaces, and the mjj and Δφjj distributions in the VBF phase space.
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Figure 06a
Exclusion contours (at 95 % CL) for Dirac-fermion dark matter produced via a contact interaction with two electroweak bosons as described in an effective field theory with two dimension-seven operators (described in text) with different charge-parity properties. Limits are set as a function of dark-matter mass and the effective field theory scale, Λ. The solid purple (green) curve shows the median of the observed (expected) limit. Also shown are limits on these operators from indirect-detection experiments. The yellow filled region around the expected limit indicates the effect of ± 1σ experimental uncertainties in the expected limit. The exclusion is based on the global fit to the pTmiss distributions in the ≥ 1 jet and VBF phase spaces, and the mjj and Δφjj distributions in the VBF phase space.
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Figure 06b
Exclusion contours (at 95 % CL) for Dirac-fermion dark matter produced via a contact interaction with two electroweak bosons as described in an effective field theory with two dimension-seven operators (described in text) with different charge-parity properties. Limits are set as a function of dark-matter mass and the effective field theory scale, Λ. The solid purple (green) curve shows the median of the observed (expected) limit. Also shown are limits on these operators from indirect-detection experiments. The yellow filled region around the expected limit indicates the effect of ± 1σ experimental uncertainties in the expected limit. The exclusion is based on the global fit to the pTmiss distributions in the ≥ 1 jet and VBF phase spaces, and the mjj and Δφjj distributions in the VBF phase space.
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Tables
Table 01
Definitions for the ≥ 1 jet and VBF fiducial phase spaces. Here mjj is the invariant mass of the two leading (in pT) jets, Δφjeti,pTmiss is the difference in azimuthal angle between pTmiss and a jet axis. The lepton veto is applied to events in the numerator (denominator) of Rmiss containing at least one (three) prompt lepton(s) or lepton(s) from τ decays. The selected leptons in the denominator are treated as invisible when calculating the pTmiss value. The central-jet veto is applied to any jets in the rapidity (y) space between the two leading jets. The dilepton invariant mass is denoted by mℓℓ.
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Table 02
Summary of the uncertainties in the measured ratio Rmiss for the lowest and highest pTmiss bins in the ≥ 1 jet phase space and the lowest and highest mjj bins in the VBF phase space. The statistical uncertainty is from the data. Statistical uncertainties in the MC simulation are included as systematic uncertainties. The uncertainties vary monotonically as a function of the respective observable.
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Auxiliary material
Figure 01a
Detector correction factor for (a) Zee and (b) Z → μμ. The green points show the bin-by-bin correction factor obtained by taking the ratio of Rmiss at particle level to that at detector level. The blue and red points show a correction factor, CZ, obtained from the ratio of the detector-level dilepton selection to the particle-level dilepton selection for the ℓ+ℓ- + jets events only. The similarity with the green points show that the majority of the correction factor arises from inefficiencies and resolutions in the lepton selection. (c) Detector-level ratio for the SM only and for SM + BSM and (d) detector corrections with and without the BSM contribution versus pTmiss in the ≥ 1 jet phase-space. The BSM model is a simplified model with an axial-vector mediator mass of 1 TeV, a WIMP mass of 150 GeV, and couplings gq = 0.25 and gχ=1.0.
png (28kB) pdf (15kB)
Figure 01b
Detector correction factor for (a) Zee and (b) Z → μμ. The green points show the bin-by-bin correction factor obtained by taking the ratio of Rmiss at particle level to that at detector level. The blue and red points show a correction factor, CZ, obtained from the ratio of the detector-level dilepton selection to the particle-level dilepton selection for the ℓ+ℓ- + jets events only. The similarity with the green points show that the majority of the correction factor arises from inefficiencies and resolutions in the lepton selection. (c) Detector-level ratio for the SM only and for SM + BSM and (d) detector corrections with and without the BSM contribution versus pTmiss in the ≥ 1 jet phase-space. The BSM model is a simplified model with an axial-vector mediator mass of 1 TeV, a WIMP mass of 150 GeV, and couplings gq = 0.25 and gχ=1.0.
png (27kB) pdf (15kB)
Figure 01c
Detector correction factor for (a) Zee and (b) Z → μμ. The green points show the bin-by-bin correction factor obtained by taking the ratio of Rmiss at particle level to that at detector level. The blue and red points show a correction factor, CZ, obtained from the ratio of the detector-level dilepton selection to the particle-level dilepton selection for the ℓ+ℓ- + jets events only. The similarity with the green points show that the majority of the correction factor arises from inefficiencies and resolutions in the lepton selection. (c) Detector-level ratio for the SM only and for SM + BSM and (d) detector corrections with and without the BSM contribution versus pTmiss in the ≥ 1 jet phase-space. The BSM model is a simplified model with an axial-vector mediator mass of 1 TeV, a WIMP mass of 150 GeV, and couplings gq = 0.25 and gχ=1.0.
png (28kB) pdf (15kB)
Figure 01d
Detector correction factor for (a) Zee and (b) Z → μμ. The green points show the bin-by-bin correction factor obtained by taking the ratio of Rmiss at particle level to that at detector level. The blue and red points show a correction factor, CZ, obtained from the ratio of the detector-level dilepton selection to the particle-level dilepton selection for the ℓ+ℓ- + jets events only. The similarity with the green points show that the majority of the correction factor arises from inefficiencies and resolutions in the lepton selection. (c) Detector-level ratio for the SM only and for SM + BSM and (d) detector corrections with and without the BSM contribution versus pTmiss in the ≥ 1 jet phase-space. The BSM model is a simplified model with an axial-vector mediator mass of 1 TeV, a WIMP mass of 150 GeV, and couplings gq = 0.25 and gχ=1.0.
png (29kB) pdf (15kB)
Figure 02a
Data/SM comparisons of the efficiency corrected number of events in (a) the W → μν control region as a function of pTmiss in the ≥ 1 jet phase-space and (b) the W → eν control region as a function of mjj in the VBF phase-space. Efficiency corrected means the leptons have been corrected for the reconstruction efficiency, giving the total number of events expected in the fiducial region of the detector, with pT > 25 GeV. The uncertainties shown are statistical only. The bottom panel shows the ratio between data and the SM prediction.
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Figure 02b
Data/SM comparisons of the efficiency corrected number of events in (a) the W → μν control region as a function of pTmiss in the ≥ 1 jet phase-space and (b) the W → eν control region as a function of mjj in the VBF phase-space. Efficiency corrected means the leptons have been corrected for the reconstruction efficiency, giving the total number of events expected in the fiducial region of the detector, with pT > 25 GeV. The uncertainties shown are statistical only. The bottom panel shows the ratio between data and the SM prediction.
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Figure 03a
(a) Covariance matrix and (b) statistical-only correlation matrix for all four measured distributions. The number on the axes indicates the bin number for each distribution.
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Figure 03b
(a) Covariance matrix and (b) statistical-only correlation matrix for all four measured distributions. The number on the axes indicates the bin number for each distribution.
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Figure 04a
The contribution from systematic uncertainties in Rmiss are shown as a function of pTmiss in the ≥ 1 jet region (a), and as a function of pTmiss (b), mjj (c) and Δφjj (d) in the VBF region.
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Figure 04b
The contribution from systematic uncertainties in Rmiss are shown as a function of pTmiss in the ≥ 1 jet region (a), and as a function of pTmiss (b), mjj (c) and Δφjj (d) in the VBF region.
png (70kB) pdf (15kB)
Figure 04c
The contribution from systematic uncertainties in Rmiss are shown as a function of pTmiss in the ≥ 1 jet region (a), and as a function of pTmiss (b), mjj (c) and Δφjj (d) in the VBF region.
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Figure 04d
The contribution from systematic uncertainties in Rmiss are shown as a function of pTmiss in the ≥ 1 jet region (a), and as a function of pTmiss (b), mjj (c) and Δφjj (d) in the VBF region.
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Figure 05a
Comparison of the particle-level Rmiss results for electrons and muons with the SM predictions as a function of pTmiss in the ≥ 1 jet region (a), and as a function of pTmiss (b), mjj (c) and Δφjj (d) in the VBF region. All statistical and systematic uncertainties are included in the green and blue error bars, where the inner tick marks are used to reflect the size of the statistical uncertainty only. The electron and muon data points are shifted relative to each other away from bin centre for visibility. The hatched bands on the SM predictions give the statistical plus theoretical uncertainty.
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Figure 05b
Comparison of the particle-level Rmiss results for electrons and muons with the SM predictions as a function of pTmiss in the ≥ 1 jet region (a), and as a function of pTmiss (b), mjj (c) and Δφjj (d) in the VBF region. All statistical and systematic uncertainties are included in the green and blue error bars, where the inner tick marks are used to reflect the size of the statistical uncertainty only. The electron and muon data points are shifted relative to each other away from bin centre for visibility. The hatched bands on the SM predictions give the statistical plus theoretical uncertainty.
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Figure 05c
Comparison of the particle-level Rmiss results for electrons and muons with the SM predictions as a function of pTmiss in the ≥ 1 jet region (a), and as a function of pTmiss (b), mjj (c) and Δφjj (d) in the VBF region. All statistical and systematic uncertainties are included in the green and blue error bars, where the inner tick marks are used to reflect the size of the statistical uncertainty only. The electron and muon data points are shifted relative to each other away from bin centre for visibility. The hatched bands on the SM predictions give the statistical plus theoretical uncertainty.
png (84kB) pdf (21kB)
Figure 05d
Comparison of the particle-level Rmiss results for electrons and muons with the SM predictions as a function of pTmiss in the ≥ 1 jet region (a), and as a function of pTmiss (b), mjj (c) and Δφjj (d) in the VBF region. All statistical and systematic uncertainties are included in the green and blue error bars, where the inner tick marks are used to reflect the size of the statistical uncertainty only. The electron and muon data points are shifted relative to each other away from bin centre for visibility. The hatched bands on the SM predictions give the statistical plus theoretical uncertainty.
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