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| CMS-SUS-19-012 ; CERN-EP-2021-097 | ||
| Search for electroweak production of charginos and neutralinos in proton-proton collisions at $\sqrt{s} = $ 13 TeV | ||
| CMS Collaboration | ||
| 27 June 2021 | ||
| JHEP 04 (2022) 147 | ||
| Abstract: A direct search for electroweak production of charginos and neutralinos is presented. Events with three or four leptons, with up to two hadronically decaying $\tau$ leptons, or two same-sign light leptons are analyzed. The data sample consists of 137 fb$^{-1}$ of proton-proton collisions with a center of mass energy of 13 TeV, recorded with the CMS detector at the LHC. The results are interpreted in terms of several simplified models. These represent a broad range of production and decay scenarios for charginos and neutralinos. A parametric neural network is used to target several of the models with large backgrounds. In addition, results using orthogonal search regions are provided for all the models, simplifying alternative theoretical interpretations of the results. Depending on the model hypotheses, charginos and neutralinos with masses up to values between 300 and 1450 GeV are excluded at 95% confidence level. | ||
| Links: e-print arXiv:2106.14246 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; CADI line (restricted) ; | ||
| We dedicate this paper to the memory of our friend and colleague Luc Pape whose seminal contributions to the CMS experiment and to searches for new physics, including supersymmetry, made this work possible. |
| Figures | |
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Figure 1:
Production of ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ with subsequent decays via sleptons (left) and a slepton and a sneutrino (right). |
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Figure 1-a:
Production of ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ with subsequent decays via sleptons. |
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Figure 1-b:
Production of ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ with subsequent decays via a slepton and a sneutrino. |
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Figure 2:
Production of ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ with subsequent decay of $\tilde{\chi}^{\pm}_1$ via a W boson and $\tilde{\chi}^{0}_{2}$ via a Z boson (left) or H boson (right). |
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Figure 2-a:
Production of ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ with subsequent decay of $\tilde{\chi}^{\pm}_1$ via a W boson and $\tilde{\chi}^{0}_{2}$ via a Z boson. |
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Figure 2-b:
Production of ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ with subsequent decay of $\tilde{\chi}^{\pm}_1$ via a W boson and $\tilde{\chi}^{0}_{2}$ via a H boson. |
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Figure 3:
Effective $\tilde{\chi}^0_1$ pair production with decays mediated by Z or H bosons. |
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Figure 3-a:
Effective $\tilde{\chi}^0_1$ pair production with decays mediated by Z bosons. |
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Figure 3-b:
Effective $\tilde{\chi}^0_1$ pair production with decays mediated by Z and H bosons. |
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Figure 3-c:
Effective $\tilde{\chi}^0_1$ pair production with decays mediated by H bosons. |
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Figure 4:
The AUC performance of the parametric neural networks for discriminating the signal from the total background predicted in simulation, as a function of $\delta m$ for the trainings targeting different signal models. The top row corresponds to the neutral network targeting signals with WZ-mediated decays with different mass ranges to show all points. The bottom row corresponds to the models with slepton-mediated decays at $x=$ 0.05 (left), $x=$ 0.5 (middle) and $x=$ 0.95 (right). Neural network models shown in blue are trained using all available $\delta m$ points, those in red are trained with all available points except the point for which the performance is shown. The models in green are not parametric and only trained to find a signal at the point where the performance is indicated. Each neural network is retrained ten times, and the mean performances are shown, with error bars indicating the standard deviation computed from ten performance values. This means that each red and green point correspond to ten neural network trainings. The entire blue curve in each figure also corresponds to ten trainings. |
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Figure 4-a:
The AUC performance of the parametric neural networks for discriminating the signal from the total background predicted in simulation, as a function of $\delta m$ for the trainings targeting different signal models. The plot corresponds to the neutral network targeting signals with WZ-mediated decays. Neural network models shown in blue are trained using all available $\delta m$ points, those in red are trained with all available points except the point for which the performance is shown. The models in green are not parametric and only trained to find a signal at the point where the performance is indicated. Each neural network is retrained ten times, and the mean performances are shown, with error bars indicating the standard deviation computed from ten performance values. This means that each red and green point correspond to ten neural network trainings. The entire blue curve in each figure also corresponds to ten trainings. |
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Figure 4-b:
The AUC performance of the parametric neural networks for discriminating the signal from the total background predicted in simulation, as a function of $\delta m$ for the trainings targeting different signal models. The plot corresponds to the neutral network targeting signals with WZ-mediated decays. Neural network models shown in blue are trained using all available $\delta m$ points, those in red are trained with all available points except the point for which the performance is shown. The models in green are not parametric and only trained to find a signal at the point where the performance is indicated. Each neural network is retrained ten times, and the mean performances are shown, with error bars indicating the standard deviation computed from ten performance values. This means that each red and green point correspond to ten neural network trainings. The entire blue curve in each figure also corresponds to ten trainings. |
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Figure 4-c:
The AUC performance of the parametric neural networks for discriminating the signal from the total background predicted in simulation, as a function of $\delta m$ for the trainings targeting different signal models. |
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Figure 4-d:
The AUC performance of the parametric neural networks for discriminating the signal from the total background predicted in simulation, as a function of $\delta m$ for the trainings targeting different signal models. The plot corresponds to the model with slepton-mediated decays at $x=$ 0.05. Neural network models shown in blue are trained using all available $\delta m$ points, those in red are trained with all available points except the point for which the performance is shown. The models in green are not parametric and only trained to find a signal at the point where the performance is indicated. Each neural network is retrained ten times, and the mean performances are shown, with error bars indicating the standard deviation computed from ten performance values. This means that each red and green point correspond to ten neural network trainings. The entire blue curve in each figure also corresponds to ten trainings. |
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Figure 4-e:
The AUC performance of the parametric neural networks for discriminating the signal from the total background predicted in simulation, as a function of $\delta m$ for the trainings targeting different signal models. The plot corresponds to the model with slepton-mediated decays at $x=$ 0.5. Neural network models shown in blue are trained using all available $\delta m$ points, those in red are trained with all available points except the point for which the performance is shown. The models in green are not parametric and only trained to find a signal at the point where the performance is indicated. Each neural network is retrained ten times, and the mean performances are shown, with error bars indicating the standard deviation computed from ten performance values. This means that each red and green point correspond to ten neural network trainings. The entire blue curve in each figure also corresponds to ten trainings. |
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Figure 4-f:
The AUC performance of the parametric neural networks for discriminating the signal from the total background predicted in simulation, as a function of $\delta m$ for the trainings targeting different signal models. The plot corresponds to the model with slepton-mediated decays at $x=$ 0.95. Neural network models shown in blue are trained using all available $\delta m$ points, those in red are trained with all available points except the point for which the performance is shown. The models in green are not parametric and only trained to find a signal at the point where the performance is indicated. Each neural network is retrained ten times, and the mean performances are shown, with error bars indicating the standard deviation computed from ten performance values. This means that each red and green point correspond to ten neural network trainings. The entire blue curve in each figure also corresponds to ten trainings. |
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Figure 5:
Observed and expected yields as functions of the output of the neural network used to search for ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with WZ-mediated decays, evaluated at $ {\delta m} = $ 20 GeV (left), 90 GeV (center), and 600 GeV (right). The legends specify the masses of $\tilde{\chi}^{0}_{2}$ and $\tilde{\chi}^0_1$ for the shown signal distributions as ($m_{\tilde{\chi}^{0}_{2}}$/$m_{\tilde{\chi}^0_1}$). The top panels show only the total uncertainty in the background prediction, while the lower panels show the total and statistical uncertainties separately. The following abbreviations are used in the legends of this and the following figures: "bkg.'' stands for background, "unc.'' for uncertainty and "obs.'' for observed. |
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Figure 5-a:
Observed and expected yields as functions of the output of the neural network used to search for ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with WZ-mediated decays, evaluated at $ {\delta m} = $ 20 GeV. The legends specify the masses of $\tilde{\chi}^{0}_{2}$ and $\tilde{\chi}^0_1$ for the shown signal distributions as ($m_{\tilde{\chi}^{0}_{2}}$/$m_{\tilde{\chi}^0_1}$). The top panels show only the total uncertainty in the background prediction, while the lower panels show the total and statistical uncertainties separately. The following abbreviations are used in the legends of this and the following figures: "bkg.'' stands for background, "unc.'' for uncertainty and "obs.'' for observed. |
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Figure 5-b:
Observed and expected yields as functions of the output of the neural network used to search for ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with WZ-mediated decays, evaluated at $ {\delta m} = $ 90 GeV. The legends specify the masses of $\tilde{\chi}^{0}_{2}$ and $\tilde{\chi}^0_1$ for the shown signal distributions as ($m_{\tilde{\chi}^{0}_{2}}$/$m_{\tilde{\chi}^0_1}$). The top panels show only the total uncertainty in the background prediction, while the lower panels show the total and statistical uncertainties separately. The following abbreviations are used in the legends of this and the following figures: "bkg.'' stands for background, "unc.'' for uncertainty and "obs.'' for observed. |
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Figure 5-c:
Observed and expected yields as functions of the output of the neural network used to search for ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with WZ-mediated decays, evaluated at $ {\delta m} = $ 600 GeV. The legends specify the masses of $\tilde{\chi}^{0}_{2}$ and $\tilde{\chi}^0_1$ for the shown signal distributions as ($m_{\tilde{\chi}^{0}_{2}}$/$m_{\tilde{\chi}^0_1}$). The top panels show only the total uncertainty in the background prediction, while the lower panels show the total and statistical uncertainties separately. The following abbreviations are used in the legends of this and the following figures: "bkg.'' stands for background, "unc.'' for uncertainty and "obs.'' for observed. |
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Figure 6:
Observed and expected yields as functions of the output of the neural network used to search for ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with slepton-mediated decays at $x = $ 0.5 (upper), 0.05 (middle), and 0.95 (lower), evaluated at $ {\delta m} = $ 50 GeV (left), 100 GeV (center), and 800 GeV (right). The legends specify the masses of $\tilde{\chi}^{0}_{2}$ and $\tilde{\chi}^0_1$ for the shown signal distributions as ($m_{\tilde{\chi}^{0}_{2}}$/$m_{\tilde{\chi}^0_1}$). |
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Figure 6-a:
Observed and expected yields as functions of the output of the neural network used to search for ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with slepton-mediated decays at $x = $ 0.5, evaluated at $ {\delta m} = $ 50 GeV. The legends specify the masses of $\tilde{\chi}^{0}_{2}$ and $\tilde{\chi}^0_1$ for the shown signal distributions as ($m_{\tilde{\chi}^{0}_{2}}$/$m_{\tilde{\chi}^0_1}$). |
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Figure 6-b:
Observed and expected yields as functions of the output of the neural network used to search for ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with slepton-mediated decays at $x = $ 0.5, evaluated at $ {\delta m} = $ 100 GeV. The legends specify the masses of $\tilde{\chi}^{0}_{2}$ and $\tilde{\chi}^0_1$ for the shown signal distributions as ($m_{\tilde{\chi}^{0}_{2}}$/$m_{\tilde{\chi}^0_1}$). |
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Figure 6-c:
Observed and expected yields as functions of the output of the neural network used to search for ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with slepton-mediated decays at $x = $ 0.5, evaluated at $ {\delta m} = $ 800 GeV. The legends specify the masses of $\tilde{\chi}^{0}_{2}$ and $\tilde{\chi}^0_1$ for the shown signal distributions as ($m_{\tilde{\chi}^{0}_{2}}$/$m_{\tilde{\chi}^0_1}$). |
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Figure 6-d:
Observed and expected yields as functions of the output of the neural network used to search for ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with slepton-mediated decays at $x = $ 0.05, evaluated at $ {\delta m} = $ 50 GeV. The legends specify the masses of $\tilde{\chi}^{0}_{2}$ and $\tilde{\chi}^0_1$ for the shown signal distributions as ($m_{\tilde{\chi}^{0}_{2}}$/$m_{\tilde{\chi}^0_1}$). |
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Figure 6-e:
Observed and expected yields as functions of the output of the neural network used to search for ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with slepton-mediated decays at $x = $ 0.05, evaluated at $ {\delta m} = $ 100 GeV. The legends specify the masses of $\tilde{\chi}^{0}_{2}$ and $\tilde{\chi}^0_1$ for the shown signal distributions as ($m_{\tilde{\chi}^{0}_{2}}$/$m_{\tilde{\chi}^0_1}$). |
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Figure 6-f:
Observed and expected yields as functions of the output of the neural network used to search for ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with slepton-mediated decays at $x = $ 0.05, evaluated at $ {\delta m} = $ 800 GeV. The legends specify the masses of $\tilde{\chi}^{0}_{2}$ and $\tilde{\chi}^0_1$ for the shown signal distributions as ($m_{\tilde{\chi}^{0}_{2}}$/$m_{\tilde{\chi}^0_1}$). |
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Figure 6-g:
Observed and expected yields as functions of the output of the neural network used to search for ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with slepton-mediated decays at $x = $ 0.95, evaluated at $ {\delta m} = $ 50 GeV. The legends specify the masses of $\tilde{\chi}^{0}_{2}$ and $\tilde{\chi}^0_1$ for the shown signal distributions as ($m_{\tilde{\chi}^{0}_{2}}$/$m_{\tilde{\chi}^0_1}$). |
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Figure 6-h:
Observed and expected yields as functions of the output of the neural network used to search for ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with slepton-mediated decays at $x = $ 0.95, evaluated at $ {\delta m} = $ 100 GeV. The legends specify the masses of $\tilde{\chi}^{0}_{2}$ and $\tilde{\chi}^0_1$ for the shown signal distributions as ($m_{\tilde{\chi}^{0}_{2}}$/$m_{\tilde{\chi}^0_1}$). |
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Figure 6-i:
Observed and expected yields as functions of the output of the neural network used to search for ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with slepton-mediated decays at $x = $ 0.95, evaluated at $ {\delta m} = $ 800 GeV. The legends specify the masses of $\tilde{\chi}^{0}_{2}$ and $\tilde{\chi}^0_1$ for the shown signal distributions as ($m_{\tilde{\chi}^{0}_{2}}$/$m_{\tilde{\chi}^0_1}$). |
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Figure 7:
Observed and expected yields across the search regions in events with two same-sign light leptons (2$\ell $SS). Several signal models are shown superimposed. They correspond to ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with slepton-mediated decays in the flavor-democratic hypothesis for a compressed $ {\delta m} = $ 50 GeV (red line) and uncompressed $ {\delta m} = $ 500 GeV (green dashed line) scenario. The legends specify the masses of $\tilde{\chi}^{0}_{2}$ and $\tilde{\chi}^0_1$ for the shown signal distributions as ($m_{\tilde{\chi}^{0}_{2}}$/$m_{\tilde{\chi}^0_1}$). |
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Figure 8:
Observed and expected yields across the search regions in events with three light leptons, at least two of which form an OSSF pair (3$\ell $A). Several signal models are shown superimposed. They correspond to ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with slepton-mediated decays in the flavor-democratic hypothesis for a compressed $ {\delta m} = $ 50 GeV (black line) and uncompressed $ {\delta m} = $ 900 GeV (blue line) scenario, and for WZ-mediated decays in an uncompressed $ {\delta m} = $ 500 GeV scenario (green line). Bins labeled as "Masked'' are not considered in the interpretation of the results because of overlap with the WZ control region. The legends specify the masses of $\tilde{\chi}^{0}_{2}$ and $\tilde{\chi}^0_1$ for the shown signal distributions as ($m_{\tilde{\chi}^{0}_{2}}$/$m_{\tilde{\chi}^0_1}$). |
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Figure 9:
Observed and expected yields across the search regions in events with three light leptons, none of which form an OSSF pair (3$\ell $B). Several signal models are shown superimposed. They correspond to ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with WH-mediated decays for scenarios corresponding to a H boson like mass splitting $ {\delta m} = $ 125 GeV (black line) and a slightly less compressed $ {\delta m} = $ 150 GeV (green dashed line) scenario. The legends specify the masses of $\tilde{\chi}^{0}_{2}$ and $\tilde{\chi}^0_1$ for the shown signal distributions as ($m_{\tilde{\chi}^{0}_{2}}$/$m_{\tilde{\chi}^0_1}$). |
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Figure 10:
Observed and expected yields across the search regions in events with a $\mu^{+} \mu^{-} $ or $\mathrm{e^{+}} \mathrm{e^{-}} $ pair and an additional ${\tau _\mathrm {h}}$ candidate (3$\ell $C). Several signal models are shown superimposed. They correspond to ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with slepton-mediated decays in the $\tau $ lepton enriched hypothesis for a compressed $ {\delta m} = $ 300 GeV (red line) and uncompressed $ {\delta m} = $ 900 GeV (green dashed line) scenario. The legends specify the masses of $\tilde{\chi}^{0}_{2}$ and $\tilde{\chi}^0_1$ for the shown signal distributions as ($m_{\tilde{\chi}^{0}_{2}}$/$m_{\tilde{\chi}^0_1}$). |
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Figure 11:
Observed and expected yields across the search regions in events with an e$^{\pm}\mu ^{\mp}$ pair and a ${\tau _\mathrm {h}}$ candidate (3$\ell $D). Several signal models are shown superimposed. They correspond to ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with slepton-mediated decays in the $\tau $ lepton dominated hypothesis for a compressed $ {\delta m} = $ 100 GeV (red line) and uncompressed $ {\delta m} = $ 500 GeV (green dashed line) scenario. The legends specify the masses of $\tilde{\chi}^{0}_{2}$ and $\tilde{\chi}^0_1$ for the shown signal distributions as ($m_{\tilde{\chi}^{0}_{2}}$/$m_{\tilde{\chi}^0_1}$). |
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Figure 12:
Observed and expected yields across the search regions in events (upper plot) with a same-sign light lepton pair and a ${\tau _\mathrm {h}}$ candidate (3$\ell $E), and (lower plot) with two ${\tau _\mathrm {h}}$ candidates and one light lepton (3$\ell $F). Several signal models are shown superimposed. They correspond to ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with slepton-mediated decays in the $\tau $ lepton dominated hypothesis for a compressed $ {\delta m} = $ 100 GeV (red line) and uncompressed $ {\delta m} = $ 500 GeV (green dashed line) scenario. The legends specify the masses of $\tilde{\chi}^{0}_{2}$ and $\tilde{\chi}^0_1$ for the shown signal distributions as ($m_{\tilde{\chi}^{0}_{2}}$/$m_{\tilde{\chi}^0_1}$). |
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Figure 12-a:
Observed and expected yields across the search regions in events with a same-sign light lepton pair and a ${\tau _\mathrm {h}}$ candidate (3$\ell $E). Several signal models are shown superimposed. They correspond to ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with slepton-mediated decays in the $\tau $ lepton dominated hypothesis for a compressed $ {\delta m} = $ 100 GeV (red line) and uncompressed $ {\delta m} = $ 500 GeV (green dashed line) scenario. The legends specify the masses of $\tilde{\chi}^{0}_{2}$ and $\tilde{\chi}^0_1$ for the shown signal distributions as ($m_{\tilde{\chi}^{0}_{2}}$/$m_{\tilde{\chi}^0_1}$). |
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Figure 12-b:
Observed and expected yields across the search regions in events with two ${\tau _\mathrm {h}}$ candidates and one light lepton (3$\ell $F). Several signal models are shown superimposed. They correspond to ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with slepton-mediated decays in the $\tau $ lepton dominated hypothesis for a compressed $ {\delta m} = $ 100 GeV (red line) and uncompressed $ {\delta m} = $ 500 GeV (green dashed line) scenario. The legends specify the masses of $\tilde{\chi}^{0}_{2}$ and $\tilde{\chi}^0_1$ for the shown signal distributions as ($m_{\tilde{\chi}^{0}_{2}}$/$m_{\tilde{\chi}^0_1}$). |
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Figure 13:
Observed and expected yields across the search regions in events with four light leptons, including 2 separate OSSF pairs (4$\ell $G). Several signal models are shown superimposed. They correspond to Higgsino pair production with decays to ZZ (blue dotted line, Higgsino mass of 300 GeV), HZ (black dashed line, Higgsino mass of 150 GeV), and HH (dark yellow line, Higgsino mass of 150 GeV). |
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Figure 14:
Observed and expected yields across the search regions in events with four light leptons not forming two OSSF pairs (4$\ell $H, upper left), events with three light leptons and a ${\tau _\mathrm {h}}$ candidate (4$\ell $I, upper right), forming two OSSF pairs (4$\ell $J, lower left), and forming one or less OSSF pairs (4$\ell $K, lower right). Several signal models are shown superimposed. They correspond to Higgsino pair production with decays to HZ (dashed black line, Higgsino mass of 150 GeV), and HH (dark yellow line, Higgsino mass of 150 GeV). |
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Figure 14-a:
Observed and expected yields across the search regions in events with four light leptons not forming two OSSF pairs (4$\ell $H). Several signal models are shown superimposed. They correspond to Higgsino pair production with decays to HZ (dashed black line, Higgsino mass of 150 GeV), and HH (dark yellow line, Higgsino mass of 150 GeV). |
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Figure 14-b:
Observed and expected yields across the search regions in events with three light leptons and a ${\tau _\mathrm {h}}$ candidate (4$\ell $I). Several signal models are shown superimposed. They correspond to Higgsino pair production with decays to HZ (dashed black line, Higgsino mass of 150 GeV), and HH (dark yellow line, Higgsino mass of 150 GeV). |
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Figure 14-c:
Observed and expected yields across the search regions in events with three light leptons forming two OSSF pairs (4$\ell $J). Several signal models are shown superimposed. They correspond to Higgsino pair production with decays to HZ (dashed black line, Higgsino mass of 150 GeV), and HH (dark yellow line, Higgsino mass of 150 GeV). |
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Figure 14-d:
Observed and expected yields across the search regions in events with three light leptons forming one or less OSSF pairs (4$\ell $K). Several signal models are shown superimposed. They correspond to Higgsino pair production with decays to HZ (dashed black line, Higgsino mass of 150 GeV), and HH (dark yellow line, Higgsino mass of 150 GeV). |
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Figure 15:
Expected test statistic distribution for a background-only fit compared to the observed test statistic value, drawn as black dots, for the search regions in each event category (upper plot) and the neural network targeting WZ-mediated superpartner decays for each $\delta m$ evaluation (lower plot). The gray shaded area represents the (symmetrized) probability density of the expected test statistic distribution, with 68 and 95% expected ranges respectively drawn in green and orange. |
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Figure 15-a:
Expected test statistic distribution for a background-only fit compared to the observed test statistic value, drawn as black dots, for the search regions in each event category. The gray shaded area represents the (symmetrized) probability density of the expected test statistic distribution, with 68 and 95% expected ranges respectively drawn in green and orange. |
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Figure 15-b:
Expected test statistic distribution for the neural network targeting WZ-mediated superpartner decays for each $\delta m$ evaluation. The gray shaded area represents the (symmetrized) probability density of the expected test statistic distribution, with 68 and 95% expected ranges respectively drawn in green and orange. |
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Figure 16:
Interpretation of the results for ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with flavor-democratic slepton-mediated decays, and the parameter governing the mass splittings being $x=$ 0.05 (upper left), $x=$ 0.5 (upper right) and $x=$ 0.95 (lower). The shading in the $m_{\tilde{\chi}^0_1}$ versus $m_{\tilde{\chi}^{0}_{2}}$ plane indicates the 95% CL upper limit on the ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production cross sections. The contours delineate the mass regions excluded at 95% CL when assuming cross section computed at NLO plus NLL. All masses below the contours are excluded. The observed, observed $ \pm $1$ \sigma _{\text {theory}}$ ($\pm $1 standard deviation of the theoretical cross sections), median expected, and expected $ \pm $1$ \sigma _{\text {experiment}}$ bounds obtained with the neural network strategy are shown in black and red. The median expected bound obtained with the search region strategy is shown in blue. The observed limits obtained in the CMS analysis using 2016 data [20] are shown in green. |
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Figure 16-a:
Interpretation of the results for ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with flavor-democratic slepton-mediated decays, and the parameter governing the mass splitting being $x=$ 0.05. The shading in the $m_{\tilde{\chi}^0_1}$ versus $m_{\tilde{\chi}^{0}_{2}}$ plane indicates the 95% CL upper limit on the ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production cross sections. The contours delineate the mass regions excluded at 95% CL when assuming cross section computed at NLO plus NLL. All masses below the contours are excluded. The observed, observed $ \pm $1$ \sigma _{\text {theory}}$ ($\pm $1 standard deviation of the theoretical cross sections), median expected, and expected $ \pm $1$ \sigma _{\text {experiment}}$ bounds obtained with the neural network strategy are shown in black and red. The median expected bound obtained with the search region strategy is shown in blue. The observed limits obtained in the CMS analysis using 2016 data [20] are shown in green. |
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Figure 16-b:
Interpretation of the results for ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with flavor-democratic slepton-mediated decays, and the parameter governing the mass splitting being $x=$ 0.5. The shading in the $m_{\tilde{\chi}^0_1}$ versus $m_{\tilde{\chi}^{0}_{2}}$ plane indicates the 95% CL upper limit on the ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production cross sections. The contours delineate the mass regions excluded at 95% CL when assuming cross section computed at NLO plus NLL. All masses below the contours are excluded. The observed, observed $ \pm $1$ \sigma _{\text {theory}}$ ($\pm $1 standard deviation of the theoretical cross sections), median expected, and expected $ \pm $1$ \sigma _{\text {experiment}}$ bounds obtained with the neural network strategy are shown in black and red. The median expected bound obtained with the search region strategy is shown in blue. The observed limits obtained in the CMS analysis using 2016 data [20] are shown in green. |
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Figure 16-c:
Interpretation of the results for ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with flavor-democratic slepton-mediated decays, and the parameter governing the mass splitting being $x=$ 0.95. The shading in the $m_{\tilde{\chi}^0_1}$ versus $m_{\tilde{\chi}^{0}_{2}}$ plane indicates the 95% CL upper limit on the ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production cross sections. The contours delineate the mass regions excluded at 95% CL when assuming cross section computed at NLO plus NLL. All masses below the contours are excluded. The observed, observed $ \pm $1$ \sigma _{\text {theory}}$ ($\pm $1 standard deviation of the theoretical cross sections), median expected, and expected $ \pm $1$ \sigma _{\text {experiment}}$ bounds obtained with the neural network strategy are shown in black and red. The median expected bound obtained with the search region strategy is shown in blue. The observed limits obtained in the CMS analysis using 2016 data [20] are shown in green. |
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Figure 17:
Interpretation of the results for ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with $\tau $-enriched slepton-mediated decays, and the parameter governing the mass splittings being $x=$ 0.05 (upper left), $x=$ 0.5 (upper right) and $x=$ 0.95 (lower). The shading in the $m_{\tilde{\chi}^0_1}$ versus $m_{\tilde{\chi}^{0}_{2}}$ plane indicates the 95% CL upper limits on the ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production cross sections. The contours delineate the mass regions excluded at 95% CL when assuming cross sections computed at NLO plus NLL. The observed, observed $ \pm $1$ \sigma _{\text {theory}}$ ($\pm $1 standard deviation of the theoretical cross sections), median expected, and expected $ \pm $1$ \sigma _{\text {experiment}}$ bounds are shown in black and red. The observed limits obtained in the CMS analysis using 2016 data [20] are shown in green. |
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Figure 17-a:
Interpretation of the results for ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with $\tau $-enriched slepton-mediated decays, and the parameter governing the mass splittings being $x=$ 0.05. The shading in the $m_{\tilde{\chi}^0_1}$ versus $m_{\tilde{\chi}^{0}_{2}}$ plane indicates the 95% CL upper limits on the ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production cross sections. The contours delineate the mass regions excluded at 95% CL when assuming cross sections computed at NLO plus NLL. The observed, observed $ \pm $1$ \sigma _{\text {theory}}$ ($\pm $1 standard deviation of the theoretical cross sections), median expected, and expected $ \pm $1$ \sigma _{\text {experiment}}$ bounds are shown in black and red. The observed limits obtained in the CMS analysis using 2016 data [20] are shown in green. |
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Figure 17-b:
Interpretation of the results for ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with $\tau $-enriched slepton-mediated decays, and the parameter governing the mass splittings being $x=$ 0.5. The shading in the $m_{\tilde{\chi}^0_1}$ versus $m_{\tilde{\chi}^{0}_{2}}$ plane indicates the 95% CL upper limits on the ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production cross sections. The contours delineate the mass regions excluded at 95% CL when assuming cross sections computed at NLO plus NLL. The observed, observed $ \pm $1$ \sigma _{\text {theory}}$ ($\pm $1 standard deviation of the theoretical cross sections), median expected, and expected $ \pm $1$ \sigma _{\text {experiment}}$ bounds are shown in black and red. The observed limits obtained in the CMS analysis using 2016 data [20] are shown in green. |
png pdf |
Figure 17-c:
Interpretation of the results for ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with $\tau $-enriched slepton-mediated decays, and the parameter governing the mass splittings being $x=$ 0.95. The shading in the $m_{\tilde{\chi}^0_1}$ versus $m_{\tilde{\chi}^{0}_{2}}$ plane indicates the 95% CL upper limits on the ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production cross sections. The contours delineate the mass regions excluded at 95% CL when assuming cross sections computed at NLO plus NLL. The observed, observed $ \pm $1$ \sigma _{\text {theory}}$ ($\pm $1 standard deviation of the theoretical cross sections), median expected, and expected $ \pm $1$ \sigma _{\text {experiment}}$ bounds are shown in black and red. The observed limits obtained in the CMS analysis using 2016 data [20] are shown in green. |
png pdf |
Figure 18:
Interpretation of the results for ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with $\tau $-dominated slepton-mediated decays, and the parameter governing the mass splittings being $x=$ 0.05 (upper left), $x=$ 0.5 (upper right) and $x=$ 0.95 (lower). The shading in the $m_{\tilde{\chi}^0_1}$ versus $m_{\tilde{\chi}^{0}_{2}}$ plane indicates the 95% CL upper limits on the ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production cross sections. The contours delineate the mass regions excluded at 95% CL when assuming cross sections computed at NLO plus NLL. The observed, observed $ \pm $1$ \sigma _{\text {theory}}$ ($\pm $1 standard deviation of the theoretical cross sections), median expected, and expected $ \pm $1$ \sigma _{\text {experiment}}$ bounds are shown in black and red. The median expected bound obtained with the search region strategy is shown in blue. The observed limits obtained in the CMS analysis using 2016 data [20] are shown in green, which only included interpretations in the $x=$ 0.5 case. |
png pdf |
Figure 18-a:
Interpretation of the results for ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with $\tau $-dominated slepton-mediated decays, and the parameter governing the mass splittings being $x=$ 0.05. The shading in the $m_{\tilde{\chi}^0_1}$ versus $m_{\tilde{\chi}^{0}_{2}}$ plane indicates the 95% CL upper limits on the ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production cross sections. The contours delineate the mass regions excluded at 95% CL when assuming cross sections computed at NLO plus NLL. The observed, observed $ \pm $1$ \sigma _{\text {theory}}$ ($\pm $1 standard deviation of the theoretical cross sections), median expected, and expected $ \pm $1$ \sigma _{\text {experiment}}$ bounds are shown in black and red. The median expected bound obtained with the search region strategy is shown in blue. |
png pdf |
Figure 18-b:
Interpretation of the results for ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with $\tau $-dominated slepton-mediated decays, and the parameter governing the mass splittings being $x=$ 0.5. The shading in the $m_{\tilde{\chi}^0_1}$ versus $m_{\tilde{\chi}^{0}_{2}}$ plane indicates the 95% CL upper limits on the ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production cross sections. The contours delineate the mass regions excluded at 95% CL when assuming cross sections computed at NLO plus NLL. The observed, observed $ \pm $1$ \sigma _{\text {theory}}$ ($\pm $1 standard deviation of the theoretical cross sections), median expected, and expected $ \pm $1$ \sigma _{\text {experiment}}$ bounds are shown in black and red. The median expected bound obtained with the search region strategy is shown in blue. The observed limits obtained in the CMS analysis using 2016 data [20] are shown in green. |
png pdf |
Figure 18-c:
Interpretation of the results for ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with $\tau $-dominated slepton-mediated decays, and the parameter governing the mass splittings being $x=$ 0.95. The shading in the $m_{\tilde{\chi}^0_1}$ versus $m_{\tilde{\chi}^{0}_{2}}$ plane indicates the 95% CL upper limits on the ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production cross sections. The contours delineate the mass regions excluded at 95% CL when assuming cross sections computed at NLO plus NLL. The observed, observed $ \pm $1$ \sigma _{\text {theory}}$ ($\pm $1 standard deviation of the theoretical cross sections), median expected, and expected $ \pm $1$ \sigma _{\text {experiment}}$ bounds are shown in black and red. The median expected bound obtained with the search region strategy is shown in blue. |
png pdf |
Figure 19:
Interpretation of the results for ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with WZ-mediated decays. The shading in the $m_{\tilde{\chi}^0_1}$ versus $m_{\tilde{\chi}^{0}_{2}}$ plane indicates the 95% CL upper limits on the ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production cross sections. The contours delineate the mass regions excluded at 95% CL when assuming cross sections computed at NLO plus NLL. The observed, observed $ \pm $1$ \sigma _{\text {theory}}$ ($\pm $1 standard deviation of the theoretical cross sections), median expected, and expected $ \pm $1$ \sigma _{\text {experiment}}$ bounds obtained with the neural network strategy are shown in black and red. The median expected bound obtained with the search region strategy is shown in blue. The observed limits obtained in the CMS analysis using 2016 data [20] are shown in green. |
png pdf |
Figure 20:
Interpretation of the results for ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production with WH-mediated decays. The shading in the $m_{\tilde{\chi}^0_1}$ versus $m_{\tilde{\chi}^{0}_{2}}$ plane indicates the 95% CL upper limits on the ${\tilde{\chi}^{\pm}_1 \tilde{\chi}^{0}_{2}}$ production cross sections. The contours delineate the mass regions excluded at 95% CL when assuming cross sections computed at NLO plus NLL. The observed, observed $ \pm $1$ \sigma _{\text {theory}}$ ($\pm $1 standard deviation of the theoretical cross sections), median expected, and expected $ \pm $1$ \sigma _{\text {experiment}}$ bounds are shown in black and red. The observed limits obtained in the CMS analysis using 2016 data [20] are shown in green. |
png pdf |
Figure 21:
Interpretation of the results for effective $\tilde{\chi}^0_1$ pair production, with ZZ-mediated decays (upper), HZ-mediated decays (middle), and HH-mediated decays (lower). The median expected upper limits (black line) are shown along with the $ \pm $1$ \sigma $ (0.16 and 0.84 quantiles, green) and $ \pm $2$ \sigma $ (0.05 and 0.95 quantiles, yellow) bands. The predicted production cross sections computed at NLO plus NLL are shown in red and the observed exclusion limits obtained in the CMS analysis using 2016 data [20] are shown in blue. |
png pdf |
Figure 21-a:
Interpretation of the results for effective $\tilde{\chi}^0_1$ pair production, with ZZ-mediated decays. The median expected upper limits (black line) are shown along with the $ \pm $1$ \sigma $ (0.16 and 0.84 quantiles, green) and $ \pm $2$ \sigma $ (0.05 and 0.95 quantiles, yellow) bands. The predicted production cross sections computed at NLO plus NLL are shown in red and the observed exclusion limits obtained in the CMS analysis using 2016 data [20] are shown in blue. |
png pdf |
Figure 21-b:
Interpretation of the results for effective $\tilde{\chi}^0_1$ pair production, with HZ-mediated decays. The median expected upper limits (black line) are shown along with the $ \pm $1$ \sigma $ (0.16 and 0.84 quantiles, green) and $ \pm $2$ \sigma $ (0.05 and 0.95 quantiles, yellow) bands. The predicted production cross sections computed at NLO plus NLL are shown in red and the observed exclusion limits obtained in the CMS analysis using 2016 data [20] are shown in blue. |
png pdf |
Figure 21-c:
Interpretation of the results for effective $\tilde{\chi}^0_1$ pair production, with HH-mediated decays. The median expected upper limits (black line) are shown along with the $ \pm $1$ \sigma $ (0.16 and 0.84 quantiles, green) and $ \pm $2$ \sigma $ (0.05 and 0.95 quantiles, yellow) bands. The predicted production cross sections computed at NLO plus NLL are shown in red and the observed exclusion limits obtained in the CMS analysis using 2016 data [20] are shown in blue. |
| Tables | |
png pdf |
Table 1:
Brief description of the categories used to classify events in the search. |
png pdf |
Table 2:
Definition of the search regions used for events with two same-sign light leptons (SSXX). The symbols ($++$) and ($-$) represent requirements on the sign of the leptons. The first ${{M_{\text {T2}}} (\ell \ell)}$ bin contains only events where ${{M_{\text {T2}}} (\ell \ell)}$ is exactly 0 [68], whereas the second bin contains events where ${{M_{\text {T2}}} (\ell \ell)}$ is larger than 0 and less than or equal to 80 GeV. The last ${{M_{\text {T2}}} (\ell \ell)}$ bin contains events where ${{M_{\text {T2}}} (\ell \ell)}$ exceeds 80 GeV. |
png pdf |
Table 3:
Definition of the search regions used for events with three light leptons, at least two of which form an OSSF pair, excluding those with 75 $ < {M_{\ell \ell}} < $ 105 GeV (AXX). |
png pdf |
Table 4:
Definition of the search regions used for events with three light leptons, at least two of which form an OSSF pair, and which satisfy 75 $ < {M_{\ell \ell}} < $ 105 GeV (AXX). |
png pdf |
Table 5:
Definition of the search regions used for events with three light leptons, none of which form an OSSF pair (BXX). |
png pdf |
Table 6:
Definition of the search regions for events with a $\mu^{+} \mu^{-} $ or $\mathrm{e^{+}} \mathrm{e^{-}} $ pair and an additional ${\tau _\mathrm {h}}$ candidate (CXX). |
png pdf |
Table 7:
Definition of the search regions for events with a e$^{\pm}\mu ^{\mp}$ pair and a ${\tau _\mathrm {h}}$ candidate (DXX). |
png pdf |
Table 8:
Definition of the search regions for events with a pair of light leptons of the same sign and a ${\tau _\mathrm {h}}$ candidate (EXX). |
png pdf |
Table 9:
Definition of the search regions for events with 2 ${\tau _\mathrm {h}}$ candidates and one light lepton (FXX). |
png pdf |
Table 10:
Definition of the search regions for events with 4 light leptons, including 2 separate OSSF pairs (GXX). |
png pdf |
Table 11:
Definition of the search regions for events with 4 leptons with one or more ${\tau _\mathrm {h}}$, or without two light-lepton OSSF pairs (XYY). |
png pdf |
Table 12:
Systematic uncertainty sources affecting the analysis, with their typical size across signal regions, and the treatment of the correlations across data-taking years. Uncertainties in the jet energy corrections and b tagging efficiencies are considered separately for signal events which use CMS fast simulation, as explained in Section {5, and for the other simulated processes. Both the overall integrated luminosity and all normalization uncertainties have effects on the predicted yields of the corresponding processes that are of the same size across all signal regions. Their quoted typical size corresponds to the size of such variations. All other uncertainties can have different effects on the predicted yields for each process and signal region. Their typical uncertainty corresponds to the range of sizes that such effects take across the analysis search regions. |
png pdf |
Table 13:
Summary of the event categories used for the interpretation of the results in terms of different models, and references to the associated figure summarizing the expected and observed 95% CL upper limits. |
| Summary |
|
A search for new physics in events with two leptons of the same sign, or with three or more leptons with up to two hadronically decaying $\tau$ leptons, is presented. A data set of proton-proton collisions with $\sqrt{s} = $ 13 TeV collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 137 fb$^{-1}$, is analyzed. Events are categorized according to the number of leptons, their signs, and flavors. Events in each category are further binned using a plethora of kinematic quantities to maximize the sensitivity of the search to an extensive set of hypotheses of supersymmetric particle production via the electroweak interaction. In events with three light leptons, of which two have opposite sign and same flavor, parametric neural networks are used to significantly enhance the sensitivity of the search to several signal hypotheses. No significant deviation from the standard model expectation is observed in any of the event categories. The results are interpreted in terms of a number of simplified models of superpartner production. Models of chargino-neutralino pair production with the neutralino forming the lightest supersymmetric particle (LSP), as well as models of effective neutralino pair production with a nearly massless gravitino as the LSP are considered. The signal topologies depend on the masses of the leptonic superpartners and the mixing of the gauge eigenstates. If left-handed sleptons lighter than the chargino existed, the chargino-neutralino pair might undergo slepton-mediated decays resulting in final states with three leptons. The results of the analysis lead to a lower limit in the chargino mass up to 1450 GeV when using a parametric neural network. Searches in events with three light leptons including an opposite-sign, same-flavor pair provide sensitivity to these models. Events with two same-sign leptons further enhance the sensitivity in experimentally challenging scenarios with small mass differences between the chargino and the LSP. If sleptons were right-handed, the chargino, or both the chargino and the neutralino, might decay almost exclusively to $\tau$ leptons. In the former scenario, a chargino mass up to 1150 GeV is excluded, while a mass up to 970 GeV is excluded in the latter. If sleptons were sufficiently heavy, charginos and neutralinos would undergo direct decay to the LSP via the emission of W, Z, or Higgs bosons. For decays of the chargino-neutralino pair via a W and a Z boson, values of the chargino mass up to 650 GeV are excluded through the use of a parametric neural network. In case of a neutralino decay via the emission of a Higgs boson, charginos with a mass below 300 GeV are excluded for nearly massless LSPs. In models of effective neutralino production we assume the neutralinos decay to almost massless gravitino LSPs via Z and Higgs bosons. This leads to excluded values of the neutralino mass up to 600 GeV. The obtained results currently provide the most stringent limits for chargino-neutralino production with mass splittings close to the Z boson mass, nearly closing the gap in the exclusion plane found in this region of the parameter space. The exclusions obtained for the slepton-mediated decays are as well the most stringent results currently for all the considered branching fraction hypotheses. In the case of the flavor-democratic decay scenario, the obtained exclusion limits of up to 1450 GeV are the overall highest exclusion values obtained for the production of electroweak superpartners. |
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