CMS-SUS-21-006 ; CERN-EP-2023-209 | ||
Search for supersymmetry in final states with disappearing tracks in proton-proton collisions at $ \sqrt{s} = $ 13 TeV | ||
CMS Collaboration | ||
28 September 2023 | ||
Phys. Rev. D 109 (2024) 072007 | ||
Abstract: A search is presented for charged, long-lived supersymmetric particles in final states with one or more disappearing tracks. The search is based on data from proton-proton collisions at a center-of-mass energy of 13 TeV collected with the CMS detector at the CERN LHC between 2016 and 2018, corresponding to an integrated luminosity of 137 fb$ ^{-1} $. The search is performed over final states characterized by varying numbers of jets, b-tagged jets, electrons, and muons. The length of signal-candidate tracks in the plane perpendicular to the beam axis is used to characterize the lifetimes of wino- and higgsino-like charginos produced in the context of the minimal supersymmetric standard model. The $ \mathrm{d} E/\mathrm{d} x $ energy loss of signal-candidate tracks is used to increase the sensitivity to charginos with a large mass and thus a small Lorentz boost. The observed results are found to be statistically consistent with the background-only hypothesis. Limits on the pair production cross section of gluinos and squarks are presented in the framework of simplified models of supersymmetric particle production and decay, and for electroweakino production based on models of wino and higgsino dark matter. The limits presented are the most stringent to date for scenarios with light third-generation squarks and a wino- or higgsino-like dark matter candidate capable of explaining the known dark matter relic density. | ||
Links: e-print arXiv:2309.16823 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ; |
Figures | |
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Figure 1:
Representative diagrams for the simplified models considered in this analysis. From left to right: T6btLL, T6tbLL, and T5btbtLL (upper); and TChiWZ, TChiWW, and TChiW (lower). The shaded circles at the production vertices represent a sum over perturbative terms. |
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Figure 1-a:
Representative diagram for the T6btLL simplified model. The shaded circle at the production vertex represents a sum over perturbative terms. |
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Figure 1-b:
Representative diagram for the T6tbLL simplified model. The shaded circle at the production vertex represents a sum over perturbative terms. |
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Figure 1-c:
Representative diagram for the T5btbtLL simplified model. The shaded circle at the production vertex represents a sum over perturbative terms. |
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Figure 1-d:
Representative diagram for the TChiWZ simplified model. The shaded circle at the production vertex represents a sum over perturbative terms. |
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Figure 1-e:
Representative diagram for the TChiWW simplified model. The shaded circle at the production vertex represents a sum over perturbative terms. |
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Figure 1-f:
Representative diagram for the TChiW simplified model. The shaded circle at the production vertex represents a sum over perturbative terms. |
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Figure 2:
The distributions of simulated events used to train and validate the BDT classifiers. The left (right) column corresponds to the Phase-0 (Phase-1) detector, and the upper (lower) row to the short (long) track category. The uncertainty bars shown for the training samples indicate the Poisson uncertainties. No events appear outside of the regions shown. |
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Figure 2-a:
Distributions of simulated events used to train and validate the BDT classifier corresponding to the Phase-0 detector in the short track category. The uncertainty bars shown for the training sample indicate the Poisson uncertainties. No events appear outside of the regions shown. |
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Figure 2-b:
Distributions of simulated events used to train and validate the BDT classifier corresponding to the Phase-1 detector in the short track category. The uncertainty bars shown for the training sample indicate the Poisson uncertainties. No events appear outside of the regions shown. |
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Figure 2-c:
Distributions of simulated events used to train and validate the BDT classifier corresponding to the Phase-0 detector in the long track category. The uncertainty bars shown for the training sample indicate the Poisson uncertainties. No events appear outside of the regions shown. |
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Figure 2-d:
Distributions of simulated events used to train and validate the BDT classifier corresponding to the Phase-1 detector in the long track category. The uncertainty bars shown for the training sample indicate the Poisson uncertainties. No events appear outside of the regions shown. |
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Figure 3:
Comparison of the $ p_{\mathrm{T}} $ distributions of DTks in the $ \kappa^{\text{low}}_{\text{high}} $ DY measurement control region for the data and background prediction for long (upper) and short (middle) showering tracks, and in the $ \kappa^{\mu\,\text{veto}}_{\mu\,\text{match}} $ DY measurement control region for long muon tracks (lower). The left (right) column corresponds to the Phase-0 (Phase-1) detector. The uncertainty bars on the ratios in the lower panels indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the sideband region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). |
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Figure 3-a:
Comparison of the $ p_{\mathrm{T}} $ distributions of DTks in the $ \kappa^{\text{low}}_{\text{high}} $ DY measurement control region for the data and background prediction for long showering tracks, corresponding to the Phase-0 detector. The uncertainty bars on the ratios in the lower panel indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the sideband region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). |
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Figure 3-b:
Comparison of the $ p_{\mathrm{T}} $ distributions of DTks in the $ \kappa^{\text{low}}_{\text{high}} $ DY measurement control region for the data and background prediction for long showering tracks, corresponding to the Phase-1 detector. The uncertainty bars on the ratios in the lower panel indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the sideband region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). |
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Figure 3-c:
Comparison of the $ p_{\mathrm{T}} $ distributions of DTks in the $ \kappa^{\text{low}}_{\text{high}} $ DY measurement control region for the data and background prediction for short showering tracks, corresponding to the Phase-0 detector. The uncertainty bars on the ratios in the lower panel indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the sideband region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). |
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Figure 3-d:
Comparison of the $ p_{\mathrm{T}} $ distributions of DTks in the $ \kappa^{\text{low}}_{\text{high}} $ DY measurement control region for the data and background prediction for short showering tracks, corresponding to the Phase-1 detector. The uncertainty bars on the ratios in the lower panel indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the sideband region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). |
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Figure 3-e:
Comparison of the $ p_{\mathrm{T}} $ distributions of DTks in the $ \kappa^{\text{low}}_{\text{high}} $ DY measurement control region for the data and background prediction in the $ \kappa^{\mu\,\text{veto}}_{\mu\,\text{match}} $ DY measurement control region for long muon tracks, corresponding to the Phase-0 detector. The uncertainty bars on the ratios in the lower panel indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the sideband region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). |
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Figure 3-f:
Comparison of the $ p_{\mathrm{T}} $ distributions of DTks in the $ \kappa^{\text{low}}_{\text{high}} $ DY measurement control region for the data and background prediction in the $ \kappa^{\mu\,\text{veto}}_{\mu\,\text{match}} $ DY measurement control region for long muon tracks, corresponding to the Phase-1 detector. The uncertainty bars on the ratios in the lower panel indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the sideband region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). |
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Figure 4:
Comparison of the $ p_{\mathrm{T}} $ distributions of DTks in the high-$ m_{\mathrm{T}} $ validation region for the data and background prediction for long (upper) and short (middle) showering tracks, and for long muon tracks (lower). The left (right) column corresponds to the Phase-0 (Phase-1) detector. The uncertainty bars on the ratios in the lower panels indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the sideband region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). |
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Figure 4-a:
Comparison of the $ p_{\mathrm{T}} $ distributions of DTks in the high-$ m_{\mathrm{T}} $ validation region for the data and background prediction for long showering tracks, corresponding to the Phase-0 detector. The uncertainty bars on the ratio in the lower panel indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the sideband region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). |
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Figure 4-b:
Comparison of the $ p_{\mathrm{T}} $ distributions of DTks in the high-$ m_{\mathrm{T}} $ validation region for the data and background prediction for long showering tracks, corresponding to the Phase-1 detector. The uncertainty bars on the ratio in the lower panel indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the sideband region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). |
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Figure 4-c:
Comparison of the $ p_{\mathrm{T}} $ distributions of DTks in the high-$ m_{\mathrm{T}} $ validation region for the data and background prediction for short showering tracks, corresponding to the Phase-0 detector. The uncertainty bars on the ratio in the lower panel indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the sideband region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). |
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Figure 4-d:
Comparison of the $ p_{\mathrm{T}} $ distributions of DTks in the high-$ m_{\mathrm{T}} $ validation region for the data and background prediction for short showering tracks, corresponding to the Phase-1 detector. The uncertainty bars on the ratio in the lower panel indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the sideband region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). |
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Figure 4-e:
Comparison of the $ p_{\mathrm{T}} $ distributions of DTks in the high-$ m_{\mathrm{T}} $ validation region for the data and background prediction for long muon tracks, corresponding to the Phase-0 detector. The uncertainty bars on the ratio in the lower panel indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the sideband region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). |
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Figure 4-f:
Comparison of the $ p_{\mathrm{T}} $ distributions of DTks in the high-$ m_{\mathrm{T}} $ validation region for the data and background prediction for long muon tracks, corresponding to the Phase-1 detector. The uncertainty bars on the ratio in the lower panel indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the sideband region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). |
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Figure 5:
Comparison of the $ p_{\mathrm{T}} $ distributions of DTks in the $ \theta^{\text{high}}_{\text{low}} $ QCD measurement control region for the data and background prediction for long (upper) and short (lower) tracks. The left (right) column corresponds to the Phase-0 (Phase-1) detector. The uncertainty bars on the ratios in the lower panels indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the control region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). |
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Figure 5-a:
Comparison of the $ p_{\mathrm{T}} $ distributions of DTks in the $ \theta^{\text{high}}_{\text{low}} $ QCD measurement control region for the data and background prediction for long tracks, corresponding to the Phase-0 detector. The uncertainty bars on the ratio in the lower panel indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the control region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). |
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Figure 5-b:
Comparison of the $ p_{\mathrm{T}} $ distributions of DTks in the $ \theta^{\text{high}}_{\text{low}} $ QCD measurement control region for the data and background prediction for long tracks, corresponding to the Phase-1 detector. The uncertainty bars on the ratio in the lower panel indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the control region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). |
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Figure 5-c:
Comparison of the $ p_{\mathrm{T}} $ distributions of DTks in the $ \theta^{\text{high}}_{\text{low}} $ QCD measurement control region for the data and background prediction for short tracks, corresponding to the Phase-0 detector. The uncertainty bars on the ratio in the lower panel indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the control region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). |
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Figure 5-d:
Comparison of the $ p_{\mathrm{T}} $ distributions of DTks in the $ \theta^{\text{high}}_{\text{low}} $ QCD measurement control region for the data and background prediction for short tracks, corresponding to the Phase-1 detector. The uncertainty bars on the ratio in the lower panel indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the control region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). |
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Figure 6:
Comparison of the $ p_{\mathrm{T}} $ distributions of DTks in events with one electron and one DTk, in a validation region with $ m_{\mathrm{T}} < $ 110 GeV and $ m_{\text{DTk},\ell} \not\in [65,110] $ GeV, for the data and background prediction for long (upper) and short (lower) tracks. The left (right) column corresponds to the Phase-0 (Phase-1) detector. The uncertainty bars on the ratios in the lower panels indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the control region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). |
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Figure 6-a:
Comparison of the $ p_{\mathrm{T}} $ distributions of DTks in events with one electron and one DTk, in a validation region with $ m_{\mathrm{T}} < $ 110 GeV and $ m_{\text{DTk},\ell} \not\in [65,110] $ GeV, for the data and background prediction for long tracks, corresponding to the Phase-0 detector. The uncertainty bars on the ratio in the lower panel indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the control region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). |
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Figure 6-b:
Comparison of the $ p_{\mathrm{T}} $ distributions of DTks in events with one electron and one DTk, in a validation region with $ m_{\mathrm{T}} < $ 110 GeV and $ m_{\text{DTk},\ell} \not\in [65,110] $ GeV, for the data and background prediction for long tracks, corresponding to the Phase-1 detector. The uncertainty bars on the ratio in the lower panel indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the control region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). |
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Figure 6-c:
Comparison of the $ p_{\mathrm{T}} $ distributions of DTks in events with one electron and one DTk, in a validation region with $ m_{\mathrm{T}} < $ 110 GeV and $ m_{\text{DTk},\ell} \not\in [65,110] $ GeV, for the data and background prediction for short tracks, corresponding to the Phase-0 detector. The uncertainty bars on the ratio in the lower panel indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the control region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). |
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Figure 6-d:
Comparison of the $ p_{\mathrm{T}} $ distributions of DTks in events with one electron and one DTk, in a validation region with $ m_{\mathrm{T}} < $ 110 GeV and $ m_{\text{DTk},\ell} \not\in [65,110] $ GeV, for the data and background prediction for short tracks, corresponding to the Phase-1 detector. The uncertainty bars on the ratio in the lower panel indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the control region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). |
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Figure 7:
Comparison in the baseline region for the long-track DTk category between the data and pre-fit predicted SM background for the $ N_{\text{jet}} $ (upper left), $ N_{\mathrm{b}\text{-jet}} $ (upper right), $ p_{\mathrm{T,hard}}^{\mathrm{miss}} $ (middle left), $ N_{\mathrm{e}} $ (middle right), $ N_{\mu} $ (lower left), and $ m_{\text{DTk};\,\mathrm{d} E/\mathrm{d} x} $ (lower right) distributions. The uncertainty bars on the ratios in the lower panels indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the control region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). For purposes of illustration, results from the T6tbLL and T5btbtLL models are shown, where the first and second numbers in parentheses indicate the squark (or gluino) mass and the LSP mass, respectively, in GeV. |
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Figure 7-a:
Comparison in the baseline region for the long-track DTk category between the data and pre-fit predicted SM background for the $ N_{\text{jet}} $ distribution. The uncertainty bars on the ratio in the lower panel indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the control region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). For purposes of illustration, results from the T6tbLL and T5btbtLL models are shown, where the first and second numbers in parentheses indicate the squark (or gluino) mass and the LSP mass, respectively, in GeV. |
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Figure 7-b:
Comparison in the baseline region for the long-track DTk category between the data and pre-fit predicted SM background for the $ N_{\mathrm{b}\text{-jet}} $ distribution. The uncertainty bars on the ratio in the lower panel indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the control region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). For purposes of illustration, results from the T6tbLL and T5btbtLL models are shown, where the first and second numbers in parentheses indicate the squark (or gluino) mass and the LSP mass, respectively, in GeV. |
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Figure 7-c:
Comparison in the baseline region for the long-track DTk category between the data and pre-fit predicted SM background for the $ p_{\mathrm{T,hard}}^{\mathrm{miss}} $ distribution. The uncertainty bars on the ratio in the lower panel indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the control region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). For purposes of illustration, results from the T6tbLL and T5btbtLL models are shown, where the first and second numbers in parentheses indicate the squark (or gluino) mass and the LSP mass, respectively, in GeV. |
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Figure 7-d:
Comparison in the baseline region for the long-track DTk category between the data and pre-fit predicted SM background for the $ N_{\mathrm{e}} $ distribution. The uncertainty bars on the ratio in the lower panel indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the control region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). For purposes of illustration, results from the T6tbLL and T5btbtLL models are shown, where the first and second numbers in parentheses indicate the squark (or gluino) mass and the LSP mass, respectively, in GeV. |
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Figure 7-e:
Comparison in the baseline region for the long-track DTk category between the data and pre-fit predicted SM background for the $ N_{\mu} $ distribution. The uncertainty bars on the ratio in the lower panel indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the control region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). For purposes of illustration, results from the T6tbLL and T5btbtLL models are shown, where the first and second numbers in parentheses indicate the squark (or gluino) mass and the LSP mass, respectively, in GeV. |
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Figure 7-f:
Comparison in the baseline region for the long-track DTk category between the data and pre-fit predicted SM background for the $ m_{\text{DTk};\,\mathrm{d} E/\mathrm{d} x} $ distribution. The uncertainty bars on the ratio in the lower panel indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the control region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). For purposes of illustration, results from the T6tbLL and T5btbtLL models are shown, where the first and second numbers in parentheses indicate the squark (or gluino) mass and the LSP mass, respectively, in GeV. |
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Figure 8:
Comparison in the baseline region for the short-track DTk category between the data and pre-fit predicted SM background for the $ N_{\text{jet}} $ (upper left), $ N_{\mathrm{b}\text{-jet}} $ (upper right), $ p_{\mathrm{T,hard}}^{\mathrm{miss}} $ (middle left), $ N_{\mathrm{e}} $ (middle right), $ N_{\mu} $ (lower left), and $ m_{\text{DTk};\,\mathrm{d} E/\mathrm{d} x} $ (lower right) distributions. The uncertainty bars on the ratios in the lower panels indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the control region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). For purposes of illustration, results from the T6tbLL and T5btbtLL models are shown, where the first and second numbers in parentheses indicate the squark (or gluino) mass and the LSP mass, respectively, in GeV. |
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Figure 8-a:
Comparison in the baseline region for the short-track DTk category between the data and pre-fit predicted SM background for the $ N_{\text{jet}} $ distribution. The uncertainty bars on the ratio in the lower panel indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the control region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). For purposes of illustration, results from the T6tbLL and T5btbtLL models are shown, where the first and second numbers in parentheses indicate the squark (or gluino) mass and the LSP mass, respectively, in GeV. |
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Figure 8-b:
Comparison in the baseline region for the short-track DTk category between the data and pre-fit predicted SM background for the $ N_{\mathrm{b}\text{-jet}} $ distribution. The uncertainty bars on the ratio in the lower panel indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the control region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). For purposes of illustration, results from the T6tbLL and T5btbtLL models are shown, where the first and second numbers in parentheses indicate the squark (or gluino) mass and the LSP mass, respectively, in GeV. |
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Figure 8-c:
Comparison in the baseline region for the short-track DTk category between the data and pre-fit predicted SM background for the $ p_{\mathrm{T,hard}}^{\mathrm{miss}} $ distribution. The uncertainty bars on the ratio in the lower panel indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the control region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). For purposes of illustration, results from the T6tbLL and T5btbtLL models are shown, where the first and second numbers in parentheses indicate the squark (or gluino) mass and the LSP mass, respectively, in GeV. |
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Figure 8-d:
Comparison in the baseline region for the short-track DTk category between the data and pre-fit predicted SM background for the $ N_{\mathrm{e}} $ distribution. The uncertainty bars on the ratio in the lower panel indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the control region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). For purposes of illustration, results from the T6tbLL and T5btbtLL models are shown, where the first and second numbers in parentheses indicate the squark (or gluino) mass and the LSP mass, respectively, in GeV. |
png pdf |
Figure 8-e:
Comparison in the baseline region for the short-track DTk category between the data and pre-fit predicted SM background for the $ N_{\mu} $ distribution. The uncertainty bars on the ratio in the lower panel indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the control region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). For purposes of illustration, results from the T6tbLL and T5btbtLL models are shown, where the first and second numbers in parentheses indicate the squark (or gluino) mass and the LSP mass, respectively, in GeV. |
png pdf |
Figure 8-f:
Comparison in the baseline region for the short-track DTk category between the data and pre-fit predicted SM background for the $ m_{\text{DTk};\,\mathrm{d} E/\mathrm{d} x} $ distribution. The uncertainty bars on the ratio in the lower panel indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the control region counts, added in quadrature with the systematic uncertainties. The leftmost (rightmost) bin includes underflow (overflow). For purposes of illustration, results from the T6tbLL and T5btbtLL models are shown, where the first and second numbers in parentheses indicate the squark (or gluino) mass and the LSP mass, respectively, in GeV. |
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Figure 9:
Comparison between the data and SM background predictions for the 49 search regions. The uncertainty bars on the ratios in the lower panels, shown for bins with nonzero entries, indicate the fractional Poisson uncertainties in the observed counts. The gray bands show the fractional Poisson uncertainties in the control region counts, added in quadrature with the systematic uncertainties. For purposes of illustration, results from the T6tbLL and T5btbtLL models are shown, where the first and second numbers in parentheses indicate the squark (or gluino) mass and the LSP mass, respectively, in GeV. |
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Figure 10:
Observed 95% CL upper limits on the signal cross sections (colored area) versus the bottom or top squark and neutralino mass for the T6tbLL (upper) and T6btLL (lower) model for a chargino proper decay length $ c\tau $ of 10 (left column) or 200 (right column) cm. Also shown are black (red) contours corresponding to the observed (expected) lower limits, including their uncertainties, on the squark and neutralino masses. |
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Figure 10-a:
Observed 95% CL upper limits on the signal cross sections (colored area) versus the bottom or top squark and neutralino mass for the T6tbLL model for a chargino proper decay length $ c\tau $ of 10 cm. Also shown are black (red) contours corresponding to the observed (expected) lower limits, including their uncertainties, on the squark and neutralino masses. |
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Figure 10-b:
Observed 95% CL upper limits on the signal cross sections (colored area) versus the bottom or top squark and neutralino mass for the T6tbLL model for a chargino proper decay length $ c\tau $ of 200 cm. Also shown are black (red) contours corresponding to the observed (expected) lower limits, including their uncertainties, on the squark and neutralino masses. |
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Figure 10-c:
Observed 95% CL upper limits on the signal cross sections (colored area) versus the bottom or top squark and neutralino mass for the T6btLL model for a chargino proper decay length $ c\tau $ of 10 cm. Also shown are black (red) contours corresponding to the observed (expected) lower limits, including their uncertainties, on the squark and neutralino masses. |
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Figure 10-d:
Observed 95% CL upper limits on the signal cross sections (colored area) versus the bottom or top squark and neutralino mass for the T6btLL model for a chargino proper decay length $ c\tau $ of 200 cm. Also shown are black (red) contours corresponding to the observed (expected) lower limits, including their uncertainties, on the squark and neutralino masses. |
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Figure 11:
Observed 95% CL upper limits on the signal cross sections (colored area) versus the gluino and neutralino mass for the T5btbtLL model for a chargino proper decay length $ c\tau $ of 10 (left column) and 200 (right column) cm. Also shown are black (red) contours corresponding to the observed (expected) lower limits, including their uncertainties, on the gluino and neutralino masses. |
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Figure 11-a:
Observed 95% CL upper limits on the signal cross sections (colored area) versus the gluino and neutralino mass for the T5btbtLL model for a chargino proper decay length $ c\tau $ of 10 cm. Also shown are black (red) contours corresponding to the observed (expected) lower limits, including their uncertainties, on the gluino and neutralino masses. |
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Figure 11-b:
Observed 95% CL upper limits on the signal cross sections (colored area) versus the gluino and neutralino mass for the T5btbtLL model for a chargino proper decay length $ c\tau $ of 200 cm. Also shown are black (red) contours corresponding to the observed (expected) lower limits, including their uncertainties, on the gluino and neutralino masses. |
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Figure 12:
Observed 95% CL upper limits on the signal cross sections (colored area) versus the chargino-LSP mass difference and the mass of the chargino for the wino (left) and higgsino (right) DM models. The black contours indicate the boundary where the observed upper limit equals the cross section of fully degenerate electroweakino production. The corresponding expected limits are shown by the red contours. The green lines represent the set of model points corresponding to the pure wino and pure higgsino models where only radiative corrections to the mass splitting are assumed. Chargino lifetimes are based on two-loop calculations. |
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Figure 12-a:
Observed 95% CL upper limits on the signal cross sections (colored area) versus the chargino-LSP mass difference and the mass of the chargino for the wino DM model. The black contour indicates the boundary where the observed upper limit equals the cross section of fully degenerate electroweakino production. The corresponding expected limits are shown by the red contour. The green line represents the set of model points corresponding to the pure wino model where only radiative corrections to the mass splitting are assumed. Chargino lifetimes are based on two-loop calculations. |
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Figure 12-b:
Observed 95% CL upper limits on the signal cross sections (colored area) versus the chargino-LSP mass difference and the mass of the chargino for the higgsino DM model. The black contour indicates the boundary where the observed upper limit equals the cross section of fully degenerate electroweakino production. The corresponding expected limits are shown by the red contour. The green line represents the set of model points corresponding to the pure higgsino model where only radiative corrections to the mass splitting are assumed. Chargino lifetimes are based on two-loop calculations. |
Tables | |
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Table 1:
Overview of the simplified models of supersymmetry considered in this analysis. |
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Table 2:
Selection criteria on the BDT classifier score and on the calorimetric energy $ E_{\text{dep}} $ associated with a disappearing track candidate for the search region (SR) and control region (CR) samples discussed in Section 8. |
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Table 3:
Definition of the search regions (SRs) for the hadronic channel. |
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Table 4:
Definition of the search regions (SRs) for the muon, electron, and $ N_{\mathrm{DTk}}\geq $ 2 channels. |
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Table 5:
The transfer factors $ \kappa^{\text{low}}_{\text{high}} $ and $ \kappa^{\mu\,\text{veto}}_{\mu\,\text{match}} $ used for the evaluation of the genuine-particle backgrounds. The ``Genuine shower'' columns refer to the $ \kappa^{\text{low}}_{\text{high}} $ factors while the ``Genuine muon'' columns refer to the $ \kappa^{\mu\,\text{veto}}_{\mu\,\text{match}} $ factors. The genuine-particle muon background is negligible for the short category of DTks. The uncertainties are statistical only. |
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Table 6:
The transfer factor $ \theta^{\text{high}}_{\text{low}} $ used for the evaluation of the spurious-particle background. The uncertainties are statistical only. |
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Table 7:
Upper: The considered sources of systematic uncertainty in the predicted signal yield and the corresponding range of values over the 49 search regions. A value of 0 is reported when the relative uncertainty is determined to be less than 0.5%. Lower: The ranges for the total pre-fit uncertainty in the predicted background counts with respect to the respective background contribution. |
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Table 8:
Predicted pre-fit background counts and uncertainties in the 49 search regions (SRs). Statistical and bin-wise systematic uncertainties are added in quadrature. The control region (CR) counts corresponding to each background category are given in the column to the left of the respective column. The numbers in parentheses for the signal points indicate the squark (or gluino) mass in GeV, the LSP mass in GeV, and $ c\tau $ for the chargino in cm, respectively. |
Summary |
A search for long-lived charginos based on data collected in proton-proton collisions at $ \sqrt{s}= $ 13 TeV, corresponding to an integrated luminosity of 137 fb$ ^{-1} $, is presented. Event yields are studied in 49 nonoverlapping search regions (SRs) defined by the number of electrons, muons, jets, and b-tagged jets, and by the hard missing transverse momentum, in final states with at least one identified disappearing track. Further categorization of the SRs is based on the approximate length of the track and on its $ \mathrm{d} E/\mathrm{d} x $ energy loss in the inner tracking detector. The analysis targets a wide variety of possible production modes appearing in simplified models of $ R $-parity conserving supersymmetry, including gluino, top squark, bottom squark, and electroweakino pair production. A machine-learning-based classifier is employed to optimally select disappearing tracks, while rejecting tracks originating from failures in the reconstruction or from combinatorial effects. Background contributions to the SRs are evaluated based on the observed yields in data control regions. The observed yields in the SRs are found to be consistent with the background-only predictions, and thus no evidence for supersymmetry is found. In the context of the examined models, bottom squarks, top squarks, and gluinos with masses as large as 1540, 1590, and 2300 GeV, respectively, are excluded. For bottom squark pair production, charginos and the lightest supersymmetric particle (LSP), considered to be essentially mass degenerate in our study, are excluded up to a mass of 850 (1210) GeV for a chargino proper decay length $ c\tau $ of 10 (200) cm. For top squark pair production, the corresponding limit on the chargino and LSP mass is 1050 (1400) GeV. These results extend the maximum limit on the LSP mass in the compressed phase space scenario by hundreds of GeV compared to the previous study [22], and extend the reach of sensitivity into mass regions where a pure wino- or pure higgsino-like LSP can account for the observed dark matter relic density. Limits are also determined for a pure wino dark matter model [29] and a pure higgsino dark matter model [32]. In the context of these two models, charginos and LSPs are excluded up to 650 GeV for the wino model and up to 210 GeV for the higgsino model. |
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