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| CMS-PAS-SUS-16-041 | ||
| Search for new physics in events with multileptons and jets in 35.9 fb$^{-1}$ of proton-proton collision data at $\sqrt{s}= $ 13 TeV | ||
| CMS Collaboration | ||
| March 2017 | ||
| Abstract: A search for new physics is carried out in events with at least 3 electrons or muons and jets. Results are based on the sample of 35.9 fb$^{-1}$ of proton-proton collision data produced by the LHC at a center-of-mass energy of 13 TeV and collected by the CMS experiment. Events are classified according to the number of b jets, missing transverse momentum, hadronic transverse energy, and the invariant mass of opposite-charge, same-flavor dilepton pairs. No significant excess above the standard model background expectation is observed. The results are interpreted using simplified models of supersymmetry. Exclusion limits are set in the context of four different simplified supersymmetric models with pair production of gluino or third generation squarks. In a model with gluino pair production, with subsequent decay into a top quark-antiquark pair and a neutralino, gluinos with masses smaller than 1610 GeV are excluded for light neutralinos. In a model with pair of bottom squarks production, the masses of sbottoms are excluded up to 840 GeV for light charginos. | ||
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Links:
CDS record (PDF) ;
CADI line (restricted) ;
These preliminary results are superseded in this paper, JHEP 02 (2018) 067. The superseded preliminary plots can be found here. |
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| Additional information on efficiencies needed for reinterpretation of these results are available here. Additional technical material for CMS speakers can be found here |
| Figures | |
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Figure 1:
Diagrams for models involving gluino pair production leading to four top quarks (a), or four quarks and two vector bosons (b) in the final state, in both cases accompanied by two LSPs. Models of bottom and top squark pair production lead to two top quarks and, respectively, W bosons (c) or SM Higgs (H) or Z bosons (d). |
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Figure 1-a:
Diagram for model involving gluino pair production leading to four top quarks in the final state, accompanied by two LSPs. |
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Figure 1-b:
Diagram for model involving gluino pair production leading to four quarks and two vector bosons in the final state, accompanied by two LSPs. |
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Figure 1-c:
Model of bottom squark pair production leading to two top quarks and W bosons. |
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Figure 1-d:
Model of top squark pair production leading to two top quarks and SM Higgs (H) or Z bosons. |
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Figure 2:
Background prediction and observation in key observables of the off-Z baseline selection: the number of (b) jets, $ {H_{\mathrm {T}}} $, $ {M_\text {T}^{\text {min}}} $, $ {E_{\mathrm {T}}^{\text {miss}}} $, the distibutions of the lepton ${p_{\mathrm {T}}}$ spectra, the flavor composition of the leptons, and the event yields in each flavour category in the event are shown. The hatched area represents the statistical and systematic uncertainties on the prediction. The lower panels show the ratio of observation to prediction. |
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Figure 2-a:
Background prediction and observation, off-Z baseline selection: the number of jets.The hatched area represents the statistical and systematic uncertainties on the prediction. The lower panel shows the ratio of observation to prediction. |
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Figure 2-b:
Background prediction and observation, off-Z baseline selection: the number of b jets.The hatched area represents the statistical and systematic uncertainties on the prediction. The lower panel shows the ratio of observation to prediction. |
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Figure 2-c:
Background prediction and observation, off-Z baseline selection: $ {H_{\mathrm {T}}} $. The hatched area represents the statistical and systematic uncertainties on the prediction. The lower panel shows the ratio of observation to prediction. |
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Figure 2-d:
Background prediction and observation, off-Z baseline selection: $ {M_\text {T}^{\text {min}}} $. The hatched area represents the statistical and systematic uncertainties on the prediction. The lower panel shows the ratio of observation to prediction. |
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Figure 2-e:
Background prediction and observation, off-Z baseline selection: $ {E_{\mathrm {T}}^{\text {miss}}} $. The hatched area represents the statistical and systematic uncertainties on the prediction. The lower panel shows the ratio of observation to prediction. |
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Figure 2-f:
Background prediction and observation, off-Z baseline selection: leading lepton ${p_{\mathrm {T}}}$. The hatched area represents the statistical and systematic uncertainties on the prediction. The lower panel shows the ratio of observation to prediction. |
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Figure 2-g:
Background prediction and observation, off-Z baseline selection: sub-leading lepton ${p_{\mathrm {T}}}$. The hatched area represents the statistical and systematic uncertainties on the prediction. The lower panel shows the ratio of observation to prediction. |
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Figure 2-h:
Background prediction and observation, off-Z baseline selection: trailing lepton ${p_{\mathrm {T}}}$. The hatched area represents the statistical and systematic uncertainties on the prediction. The lower panel shows the ratio of observation to prediction. |
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Figure 2-i:
Background prediction and observation, off-Z baseline selection: Event yields in each flavour category in the event. The hatched area represents the statistical and systematic uncertainties on the prediction. The lower panel shows the ratio of observation to prediction. |
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Figure 3:
Background prediction and observation in key observables of the on-Z baseline selection: the number of (b) jets, $ {H_{\mathrm {T}}} $, $ {M_\text {T}^{\text {min}}} $, $ {E_{\mathrm {T}}^{\text {miss}}} $, the distibutions of the lepton ${p_{\mathrm {T}}}$ spectra, the flavor composition of the leptons, and the event yields in each flavour category in the event are shown. The hatched area represents the statistical and systematic uncertainties on the prediction. The lower panels show the ratio of observation to prediction. |
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Figure 3-a:
Background prediction and observation, on-Z baseline selection: the number of jets.The hatched area represents the statistical and systematic uncertainties on the prediction. The lower panel shows the ratio of observation to prediction. |
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Figure 3-b:
Background prediction and observation, on-Z baseline selection: the number of b jets.The hatched area represents the statistical and systematic uncertainties on the prediction. The lower panel shows the ratio of observation to prediction. |
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Figure 3-c:
Background prediction and observation, on-Z baseline selection: $ {H_{\mathrm {T}}} $. The hatched area represents the statistical and systematic uncertainties on the prediction. The lower panel shows the ratio of observation to prediction. |
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Figure 3-d:
Background prediction and observation, on-Z baseline selection: $ {M_\text {T}^{\text {min}}} $. The hatched area represents the statistical and systematic uncertainties on the prediction. The lower panel shows the ratio of observation to prediction. |
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Figure 3-e:
Background prediction and observation, on-Z baseline selection: $ {E_{\mathrm {T}}^{\text {miss}}} $. The hatched area represents the statistical and systematic uncertainties on the prediction. The lower panel shows the ratio of observation to prediction. |
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Figure 3-f:
Background prediction and observation, on-Z baseline selection: leading lepton ${p_{\mathrm {T}}}$. The hatched area represents the statistical and systematic uncertainties on the prediction. The lower panel shows the ratio of observation to prediction. |
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Figure 3-g:
Background prediction and observation, on-Z baseline selection: sub-leading lepton ${p_{\mathrm {T}}}$. The hatched area represents the statistical and systematic uncertainties on the prediction. The lower panel shows the ratio of observation to prediction. |
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Figure 3-h:
Background prediction and observation, on-Z baseline selection: trailing lepton ${p_{\mathrm {T}}}$. The hatched area represents the statistical and systematic uncertainties on the prediction. The lower panel shows the ratio of observation to prediction. |
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Figure 3-i:
Background prediction and observation, on-Z baseline selection: Event yields in each flavour category in the event. The hatched area represents the statistical and systematic uncertainties on the prediction. The lower panel shows the ratio of observation to prediction. |
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Figure 4:
Background prediction and observation in the 23 off-Z signal regions and in the 23 on-Z signal regions. The hatched area represents the statistical and systematic uncertainties on the prediction. The lower panels show the ratio of observation to prediction. |
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Figure 4-a:
Background prediction and observation in the 23 off-Z signal regions. The hatched area represents the statistical and systematic uncertainties on the prediction. The lower panel shows the ratio of observation to prediction. |
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Figure 4-b:
Background prediction and observation in the 23 on-Z signal regions. The hatched area represents the statistical and systematic uncertainties on the prediction. The lower panel shows the ratio of observation to prediction. |
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Figure 5:
Excluded region at 95% confidence in the $m(\tilde{\chi}^0)$ versus $m(\tilde{\mathrm{g}})$ plane for the simplified models of gluino pair production with four top quarks (a) and a VV + jets (b) in the final state. The excluded regions are to the left and below the observed and expected limit curves. The color scale indicates the excluded cross section at a given point in the mass plane. |
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Figure 5-a:
Excluded region at 95% confidence in the $m(\tilde{\chi}^0)$ versus $m(\tilde{\mathrm{g}})$ plane for the simplified models of gluino pair production with four top quarks in the final state. The excluded regions are to the left and below the observed and expected limit curves. The color scale indicates the excluded cross section at a given point in the mass plane. |
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Figure 5-b:
Excluded region at 95% confidence in the $m(\tilde{\chi}^0)$ versus $m(\tilde{\mathrm{g}})$ plane for the simplified models of gluino pair production with VV + jets in the final state. The excluded regions are to the left and below the observed and expected limit curves. The color scale indicates the excluded cross section at a given point in the mass plane. |
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Figure 6:
Excluded region at 95% confidence in the $m(\tilde{\chi}^0)$ versus $m( \tilde{\mathrm{b}})$ plane for the simplified models of $\tilde{\mathrm{b}}$ pair production with two top quarks and two W boson + jets in the final state. The excluded regions are to the left and below the observed and expected limit curves. The color scale indicates the excluded cross section at a given point in the mass plane. |
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Figure 7:
Excluded region at 95% confidence in the $m( \tilde{\mathrm{t}}_2)$ versus $m( \tilde{\mathrm{t}}_1)$ plane for the simplified models of $\tilde{\mathrm{t}}_2$ pair production with 2 top quarks and two Z or H boson + jets in the final state. Different branching ratio of the decay $ \tilde{\mathrm{t}}_2 \rightarrow \tilde{\mathrm{t}}_1 \mathrm{Z}$ are considered: 0% (a), 50% (b) and 100% (c). The excluded regions are to the left and below the observed and expected limit curves. The color scale indicates the excluded cross section at a given point in the mass plane. |
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Figure 7-a:
Excluded region at 95% confidence in the $m( \tilde{\mathrm{t}}_2)$ versus $m( \tilde{\mathrm{t}}_1)$ plane for the simplified models of $\tilde{\mathrm{t}}_2$ pair production with 2 top quarks and two Z or H boson + jets in the final state. Different branching ratio of the decay $ \tilde{\mathrm{t}}_2 \rightarrow \tilde{\mathrm{t}}_1 \mathrm{Z}$ are considered: 0%. The excluded regions are to the left and below the observed and expected limit curves. The color scale indicates the excluded cross section at a given point in the mass plane. |
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Figure 7-b:
Excluded region at 95% confidence in the $m( \tilde{\mathrm{t}}_2)$ versus $m( \tilde{\mathrm{t}}_1)$ plane for the simplified models of $\tilde{\mathrm{t}}_2$ pair production with 2 top quarks and two Z or H boson + jets in the final state. Different branching ratio of the decay $ \tilde{\mathrm{t}}_2 \rightarrow \tilde{\mathrm{t}}_1 \mathrm{Z}$ are considered: 50%. The excluded regions are to the left and below the observed and expected limit curves. The color scale indicates the excluded cross section at a given point in the mass plane. |
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Figure 7-c:
Excluded region at 95% confidence in the $m( \tilde{\mathrm{t}}_2)$ versus $m( \tilde{\mathrm{t}}_1)$ plane for the simplified models of $\tilde{\mathrm{t}}_2$ pair production with 2 top quarks and two Z or H boson + jets in the final state. Different branching ratio of the decay $ \tilde{\mathrm{t}}_2 \rightarrow \tilde{\mathrm{t}}_1 \mathrm{Z}$ are considered: 100%. The excluded regions are to the left and below the observed and expected limit curves. The color scale indicates the excluded cross section at a given point in the mass plane. |
| Tables | |
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Table 1:
Summary of all cuts used in baseline selection |
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Table 2:
Summary of the definition of the signal regions. The minimum $ {E_{\mathrm {T}}^{\text {miss}}} $ requirement is raised from 50 to 70 GeV only for on-Z SR1 and SR5. The dagger sign indicates signal regions that are further subdivided at $ {M_\text {T}^{\text {min}}} = $ 120 GeV. The search regions are mirrored in on- and off-Z region. |
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Table 3:
Definition of super signal regions. A simpler classification is proposed for reinterpretations, depending on the presence of a Z candidate and the number of b jets, along with additional simultaneous requirements on $ {M_\text {T}^{\text {min}}} $, $ {E_{\mathrm {T}}^{\text {miss}}} $ and $ {H_{\mathrm {T}}} $. |
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Table 4:
Systematic uncertainties and their effect on the event yields of each affected process. |
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Table 5:
Observed and expected yields in the off-Z search regions with the 35.9 fb$^{-1}$ of data. The uncertainties shown are statistical then systematic. |
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Table 6:
Observed and expected yields in the on-Z search regions with the 35.9 fb$^{-1}$ of data. The uncertainties shown are statistical then systematic. |
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Table 7:
Observed and expected yields in the super search regions with the 35.9 fb$^{-1}$ of data. The uncertainties shown are statistical then systematic. |
| Summary |
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A search for beyond the standard model physics in final states with $\geq $3 leptons, electrons or muons, using 35.9 fb$^{-1}$ of data collected with the CMS detector in 2016 at $ \sqrt{s} = $ 13 TeV has been presented. The analysis makes use of control regions in data to estimate reducible backgrounds and to validate simulation for use in estimating irreducible background processes. To maximize sensitivity to a broad range of possible signal models, 46 exclusive signal regions have been investigated. No significant deviation from the expected standard model background has been observed. In the absence of any observed excesses in the data, the result has been interpreted using a simplified gluino-pair production model that features cascade decays producing four top quarks in the final state. In this model, we exclude gluinos with a mass of up to 1610 GeV in the case of a massless LSP. The maximum excluded LSP mass is 900 GeV. In both masses, this represents an improvement of the order of 435 GeV and 250 GeV, respectively, compared to the exclusion limit set in a similar search based on 2.3 fb$^{-1}$ collected with the CMS detector in 2015 [15]. For the simplified model with gluino-gluino production and light jets and two vector bosons in the final state, gluino masses up to 1160 GeV and neutralino masses up to 650 GeV can be excluded. The limit on gluino mass for a light neutralino extends the corresponding limit from the previous analysis by about 335 GeV and 150 GeV, respectively. For simplified model for ${\widetilde{\text{b}}} $ pair production ${\widetilde{\text{b}}} $ masses up to 840 GeV is excluding in case of low mass of ${\widetilde{\chi}^\pm} $, while ${\widetilde{\chi}^\pm} $ masses are excluded up to 740 GeV, which are extending by 390 and 440 GeV for both sparticles. And finally for top squarks pair production model with further decay into 2 top quarks and Higgs or Z boson, the$ {\widetilde{\text{t}}_2} $ masses are excluded up to 580, 570 and 910 GeV for the models with the ${\widetilde{\text{t}}_2} \rightarrow{\widetilde{\text{t}}_1} \mathrm{Z}$ BR of 0%, 50% and 100% respectively, while ${\widetilde{\text{t}}_1} $ masses are excluded up to 40, 10 and 300 GeV for the same branching ratios. |
| Additional Tables | |
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Additional Table 1:
Cutflow table for the gluino pair production model with four top quarks in the final state, assuming gluino and LSP masses equal to 1500 and 200 GeV, respectively. The last two lines correspond to the most populated search regions. The yields correspond to the integrated luminosity of 35.9 fb$^{-1}$ and the assumed cross section for this model is 0.0142 pb. |
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Additional Table 2:
Cutflow table for the gluino pair production model with two vector bosons and light jets in the final state, assuming gluino and LSP masses equal to 1200 and 400 GeV, respectively. The last two lines correspond to the most populated search regions. The yields correspond to the integrated luminosity of 35.9 fb$^{-1}$. The assumed cross section for this model is 0.0856 pb, with branching fraction values of 2/3 and 1/3 for $ \tilde{ \mathrm{g} } \rightarrow {\tilde{\chi}^\pm } \mathrm{ q \bar{q}'} $ and $ \tilde{ \mathrm{g} } \rightarrow {\tilde{\chi}^0_2} \mathrm{ q \bar{q} } $ respectively. |
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Compact Muon Solenoid LHC, CERN |
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