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CMS-PAS-SUS-16-020

Search for SUSY in same-sign dilepton events with 12.9 fb$^{-1}$ of pp collision data at 13 TeV

CMS Collaboration

August 2016

Abstract: A search for new physics is performed using events with a pair of isolated same-sign leptons and jets in the final state using the CMS detector at the LHC. Results are based on a sample of proton-proton collisions at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 12.9 fb$^{-1}$. In order to be sensitive to a wide variety of possible signals beyond the standard model, we consider multiple search regions defined by the missing transverse energy, the hadronic transverse energy, the transverse mass, the number of jets and b quark jets, and the transverse momenta of the leptons in the event. No excess above the standard model background expectation is observed and constraints are set on the gluino pair production cross section; model independent limits and selection efficiencies are also provided for additional model testing.

Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ;

Additional information on efficiencies needed for reinterpretation of these results are available here.

Figures
png pdf	Figure 1-a: Diagrams for SUSY processes possibly yielding two same-sign leptons in the final state.
png pdf	Figure 1-b: Diagrams for SUSY processes possibly yielding two same-sign leptons in the final state.
png pdf	Figure 2-a: Distributions for the main analysis variables after the baseline selection with ${\mathcal {L}} =$ 12.9 fb$^{-1}$. The shaded area represents the total uncertainty in the background prediction.
png pdf	Figure 2-b: Distributions for the main analysis variables after the baseline selection with ${\mathcal {L}} =$ 12.9 fb$^{-1}$. The shaded area represents the total uncertainty in the background prediction.
png pdf	Figure 2-c: Distributions for the main analysis variables after the baseline selection with ${\mathcal {L}} =$ 12.9 fb$^{-1}$. The shaded area represents the total uncertainty in the background prediction.
png pdf	Figure 2-d: Distributions for the main analysis variables after the baseline selection with ${\mathcal {L}} =$ 12.9 fb$^{-1}$. The shaded area represents the total uncertainty in the background prediction.
png pdf	Figure 2-e: Distributions for the main analysis variables after the baseline selection with ${\mathcal {L}} =$ 12.9 fb$^{-1}$. The shaded area represents the total uncertainty in the background prediction.
png pdf	Figure 3-a: Event yields in HH (a), HL (b), and LL (c) signal regions with ${\mathcal {L}} =$ 12.9 fb$^{-1}$. The shaded area represents the total uncertainty in the background prediction.
png pdf	Figure 3-b: Event yields in HH (a), HL (b), and LL (c) signal regions with ${\mathcal {L}} =$ 12.9 fb$^{-1}$. The shaded area represents the total uncertainty in the background prediction.
png pdf	Figure 3-c: Event yields in HH (a), HL (b), and LL (c) signal regions with ${\mathcal {L}} =$ 12.9 fb$^{-1}$. The shaded area represents the total uncertainty in the background prediction.
png pdf	Figure 4: Exclusion regions at 95% CL in the plane of $m( {\tilde{\chi}^{0}} )$ versus $m( \tilde{\mathrm{g}} )$ for the T1tttt simplified model. The right-hand-side color scale indicates the excluded cross section values for a given point in the SUSY particle mass plane. Observed and expected limit lines indicate the boundaries of excluded regions (to the left and below the curve).
png pdf	Figure 5-a: Exclusion regions at 95% CL in the plane of $m( {\tilde{\chi}^{0}} )$ versus $m( \tilde{\mathrm{g}} )$ for the T5qqqqWW simplified model with $m_{\tilde{\chi}^\pm_1} = 0.5(m_{ \tilde{\mathrm{g}} } + m_{ {\tilde{\chi}^{0}} })$ (a) and $m_{\tilde{\chi}^\pm_1}=m_{ {\tilde{\chi}^{0}} }$ + 20 GeV (b). The right-hand-side color scale indicates the excluded cross section values for a given point in the SUSY particle mass plane. Observed and expected limit lines indicate the boundaries of excluded regions (to the left and below the curve).
png pdf	Figure 5-b: Exclusion regions at 95% CL in the plane of $m( {\tilde{\chi}^{0}} )$ versus $m( \tilde{\mathrm{g}} )$ for the T5qqqqWW simplified model with $m_{\tilde{\chi}^\pm_1} = 0.5(m_{ \tilde{\mathrm{g}} } + m_{ {\tilde{\chi}^{0}} })$ (a) and $m_{\tilde{\chi}^\pm_1}=m_{ {\tilde{\chi}^{0}} }$ + 20 GeV (b). The right-hand-side color scale indicates the excluded cross section values for a given point in the SUSY particle mass plane. Observed and expected limit lines indicate the boundaries of excluded regions (to the left and below the curve).
png pdf	Figure 6-a: Limits on $\sigma \mathcal {A} \epsilon $ at 95% CL.
png pdf	Figure 6-b: Limits on $\sigma \mathcal {A} \epsilon $ at 95% CL.

Tables
png pdf	Table 1: Multi-isolation working points used in the analysis.
png pdf	Table 2: Kinematic and fiducial requirements on tight (loose) leptons and jets that are used in the analysis.
png pdf	Table 3: Signal region definitions for the HH lepton selection.
png pdf	Table 4: Signal region definitions for the HL lepton selection.
png pdf	Table 5: Signal region definitions for the LL lepton selection. The $ {H_{\mathrm {T}}} >$ 300 GeV requirement is applied in all search regions in this category.
png pdf	Table 6: Summary of the sources of uncertainties and their effect on the yield in the signal regions. Reported values are representative for the most relevant signal regions.
png pdf	Table 7: Event yields in the signal regions with ${\mathcal {L}} =$ 12.9 fb$^{-1}$.

Summary

We have presented the results of a search for new physics in same-sign dilepton events using the CMS detector at the LHC, based on a proton-proton collision data sample at $\sqrt{s} =$ 13 TeV corresponding to an integrated luminosity of 12.9 fb$^{-1}$, collected in the first half of 2016. The data are analyzed in exclusive signal regions defined with different selections on lepton and event kinematic variables, as well as jet and b jet multiplicities. No significant deviations from the standard model expectations are observed. The results are used to set upper limits on the gluino pair production of supersymmetric particles in two simplified models. Gluino masses are probed up to 1350 GeV, extending the sensitivity of previous dilepton searches. In addition, 95% confidence level limits of 1.4 pb and 57 fb are set on the production cross section of two SS top quarks and $\mathrm{ t \bar{t} }\mathrm{ t \bar{t} }$, respectively, and model independent limits and selection efficiencies are provided to allow further interpretations of the results.

Additional Figures
png pdf	Additional Figure 1: Event yields in the HH search regions for a few SUSY signal models.
png pdf	Additional Figure 2: Comparison of observed and predicted events in the $\mathrm{ Z \rightarrow e^{\pm }e^{\pm } }$ control region as a function of the electron ${p_{\mathrm {T}}} $. The prediction is obtained from $\mathrm{ Z \rightarrow e^{+}e^{-} }$ events reweighted by the charge misidentification probability.
png pdf	Additional Figure 3: ${E_{\mathrm {T}}^{\text {miss}}}$ distribution in the WZ control region, defined requiring at least two jets, no b jets, ${E_{\mathrm {T}}^{\text {miss}}} > $ 30 GeV, and three leptons, where two of the leptons form a same-flavor, opposite-sign pair with an invariant mass within 15 GeV of the Z boson mass.
png pdf	Additional Figure 4: Number of jets distribution in the WZ control region, defined requiring at least two jets, no b jets, ${E_{\mathrm {T}}^{\text {miss}}} > $ 30 GeV, and three leptons, where two of the leptons form a same-flavor, opposite-sign pair with an invariant mass within 15 GeV of the Z boson mass.

Additional Tables
png pdf	Additional Table 1: Cut flow table for the 'tttt' model assuming gluino and LSP masses equal to 1400 and 1000 GeV, respectively. The last two lines correspond to the most populated search regions. The assumed cross section for this model is 0.0253 pb.
png pdf	Additional Table 2: Cut flow table for the 'tttt' model assuming gluino and LSP masses equal to 1500 and 200 GeV, respectively. The last two lines correspond to the most populated search regions. The assumed cross section for this model is 0.0142 pb.
png pdf	Additional Table 3: Cut flow table for the 'qqqqWW' model with $ m_{ \tilde{\chi }^\pm _1 } = 0.5(m_{ \tilde{g} } + m_{ \tilde{\chi }^0_1} )$ assuming gluino and LSP masses equal to 1000 and 700 GeV, respectively. The last two lines correspond to the most populated search regions. The assumed cross section for this model is 0.3254 pb.
png pdf	Additional Table 4: Cut flow table for the 'qqqqWW' model with $m_{ \tilde{\chi }^\pm _1 } = 0.5(m_{ \tilde{g} } + m_{ \tilde{\chi }^0_1} )$ assuming gluino and LSP masses equal to 1100 and 200 GeV, respectively. The last two lines correspond to the most populated search regions. The assumed cross section for this model is 0.1635 pb.
png pdf	Additional Table 5: Cut flow table for the 'qqqqWW' model with $m_{ \tilde{\chi }^\pm _1 } = 0.5(m_{ \tilde{g} } + m_{ \tilde{\chi }^0_1} )$ assuming gluino and LSP masses equal to 1200 and 400 GeV, respectively. The last two lines correspond to the most populated search regions. The assumed cross section for this model is 0.0856 pb.
png pdf	Additional Table 6: Cut flow table for the 'qqqqWW' model with $m_{ \tilde{\chi }^\pm _1 } = m_{ \tilde{\chi }^0_1} $ + 20 GeV assuming gluino and LSP masses equal to 1400 and 200 GeV, respectively. The last two lines correspond to the most populated search regions. The assumed cross section for this model is 0.0253 pb.
png pdf	Additional Table 7: Cut flow table for the 'qqqqWW' model with $m_{ \tilde{\chi }^\pm _1 } = m_{ \tilde{\chi }^0_1} $ + 20 GeV assuming gluino and LSP masses equal to 1000 and 700 GeV, respectively. The last two lines correspond to the most populated search regions. The assumed cross section for this model is 0.3254 pb.

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