Search for the pair production of long-lived supersymmetric partners of the tau lepton in proton-proton collisions at $\sqrt{s}$ = 13 TeV

The CMS collaboration
CMS-EXO-24-020, 2026.

Abstract (data abstract)
Gauge-mediated supersymmetry-breaking models provide a strong motivation to search for a supersymmetric partner of the tau lepton (stau) with a macroscopic lifetime. Long-lived stau decays produce tau leptons that are displaced from the primary proton-proton interaction vertex, leading to an unconventional signature. This paper presents a search for the direct production of long-lived staus decaying within the CMS tracker volume in proton-proton collisions at $\sqrt{s}=13$ TeV, performed for the first time with an identification algorithm based on a graph neural network dedicated to displaced tau leptons. The data sample, corresponding to an integrated luminosity of 138\fbinv, was recorded with the CMS experiment at the CERN LHC between 2016 and 2018. This search excludes, at 95% confidence level, stau masses, $m_{\tilde{\tau}}$, in the 126--260 (90--425) GeV range for a proper decay length of 50 mm in the maximally mixed (mass-degenerate) scenario, while for $m_{\tilde{\tau}} = 200$ GeV, stau proper decay lengths are excluded in the range 21--94 (6--333) mm. These results improve the exclusion limits compared to previous searches, and extend the parameter space explored in the context of supersymmetry.

  • Figure 4a

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    Distributions of $p_\text{T, j2}$ for data and the predicted background, in the signal region. The signal distributions expected in the...

  • Figure 4b

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    Distributions of $p^\text{miss}_\text{T}$ for data and the predicted background, in the signal region. The signal distributions expected in the maximally...

  • Figure 4c

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    Distributions of $m_\text{T2}$ for data and the predicted background, in the signal region. The signal distributions expected in the maximally...

  • Figure 5

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    The observed and predicted event yields in the eight BRT1 bins, as defined in Table 2. The signal yields expected...

  • Figure 6a (prefit yields)

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    The observed and predicted event yields in the eight SR bins as defined in Table 2. The signal yields expected...

  • Figure 6b (postfit yields)

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    The observed and predicted event yields in the eight SR bins as defined in Table 2. The signal yields expected...

  • Figure 7a (observed limits, maximally mixed)

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    The observed upper limits in the $(m_{\tilde{\tau}} [\text{GeV}], c\tau_{0} [\text{mm}])$ plane, for the maximally mixed scenario.

  • Figure 7a (observed exclusion, maximally mixed)

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    The set of $(m_{\tilde{\tau}} [\text{GeV}], c\tau_{0} [\text{mm}])$ points lying on the observed exclusion contour, for the maximally mixed scenario.

  • Figure 7a (observed$+1\sigma$ exclusion, maximally mixed)

    10.17182/hepdata.166010.v1/t9

    The set of $(m_{\tilde{\tau}} [\text{GeV}], c\tau_{0} [\text{mm}])$ points lying on the observed$+1\sigma$ exclusion contour, for the maximally mixed scenario.

  • Figure 7a (observed$-1\sigma$ exclusion, maximally mixed)

    10.17182/hepdata.166010.v1/t10

    The set of $(m_{\tilde{\tau}} [\text{GeV}], c\tau_{0} [\text{mm}])$ points lying on the observed$-1\sigma$ exclusion contour, for the maximally mixed scenario.

  • Figure 7a (expected exclusion, maximally mixed)

    10.17182/hepdata.166010.v1/t11

    The set of $(m_{\tilde{\tau}} [\text{GeV}], c\tau_{0} [\text{mm}])$ points lying on the expected exclusion contour, for the maximally mixed scenario.

  • Figure 7a (expected$+1\sigma$ exclusion, maximally mixed)

    10.17182/hepdata.166010.v1/t12

    The set of $(m_{\tilde{\tau}} [\text{GeV}], c\tau_{0} [\text{mm}])$ points lying on the expected$+1\sigma$ exclusion contour, for the maximally mixed scenario.

  • Figure 7a (expected$-1\sigma$ exclusion, maximally mixed)

    10.17182/hepdata.166010.v1/t13

    The set of $(m_{\tilde{\tau}} [\text{GeV}], c\tau_{0} [\text{mm}])$ points lying on the expected$-1\sigma$ exclusion contour, for the maximally mixed scenario.

  • Figure 7a (expected$-2\sigma$ exclusion, maximally mixed)

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    The set of $(m_{\tilde{\tau}} [\text{GeV}], c\tau_{0} [\text{mm}])$ points lying on the expected$-2\sigma$ exclusion contour, for the maximally mixed scenario.

  • Figure 7b (observed limits, mass-degenerate)

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    The observed upper limits in the $(m_{\tilde{\tau}} [\text{GeV}], c\tau_{0} [\text{mm}])$ plane, for the mass-degenerate scenario.

  • Figure 7b (observed exclusion, mass-degenerate)

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    The set of $(m_{\tilde{\tau}} [\text{GeV}], c\tau_{0} [\text{mm}])$ points lying on the observed exclusion contour, for the mass-degenerate scenario.

  • Figure 7b (observed$+1\sigma$ exclusion, mass-degenerate)

    10.17182/hepdata.166010.v1/t17

    The set of $(m_{\tilde{\tau}} [\text{GeV}], c\tau_{0} [\text{mm}])$ points lying on the observed$+1\sigma$ exclusion contour, for the mass-degenerate scenario.

  • Figure 7b (observed$-1\sigma$ exclusion, mass-degenerate)

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    The set of $(m_{\tilde{\tau}} [\text{GeV}], c\tau_{0} [\text{mm}])$ points lying on the observed$-1\sigma$ exclusion contour, for the mass-degenerate scenario.

  • Figure 7b (expected exclusion, mass-degenerate)

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    The set of $(m_{\tilde{\tau}} [\text{GeV}], c\tau_{0} [\text{mm}])$ points lying on the expected exclusion contour, for the mass-degenerate scenario.

  • Figure 7b (expected$+1\sigma$ exclusion, mass-degenerate)

    10.17182/hepdata.166010.v1/t20

    The set of $(m_{\tilde{\tau}} [\text{GeV}], c\tau_{0} [\text{mm}])$ points lying on the expected$+1\sigma$ exclusion contour, for the mass-degenerate scenario.

  • Figure 7b (expected$-1\sigma$ exclusion, mass-degenerate)

    10.17182/hepdata.166010.v1/t21

    The set of $(m_{\tilde{\tau}} [\text{GeV}], c\tau_{0} [\text{mm}])$ points lying on the expected$-1\sigma$ exclusion contour, for the mass-degenerate scenario.

  • Figure 7b (expected$+2\sigma$ exclusion, mass-degenerate)

    10.17182/hepdata.166010.v1/t22

    The set of $(m_{\tilde{\tau}} [\text{GeV}], c\tau_{0} [\text{mm}])$ points lying on the expected$+2\sigma$ exclusion contour, for the mass-degenerate scenario.

  • Figure 7b (expected$-2\sigma$ exclusion, mass-degenerate)

    10.17182/hepdata.166010.v1/t23

    The set of $(m_{\tilde{\tau}} [\text{GeV}], c\tau_{0} [\text{mm}])$ points lying on the expected$-2\sigma$ exclusion contour, for the mass-degenerate scenario.

  • Figure 8a ($c\tau_{0}=10$ mm, maximally mixed)

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    Cross section upper limits at 95% CL for the pair production of long-lived staus in the maximally mixed scenario, as...

  • Figure 8b ($c\tau_{0}=30$ mm, maximally mixed)

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    Cross section upper limits at 95% CL for the pair production of long-lived staus in the maximally mixed scenario, as...

  • Figure 8c ($c\tau_{0}=50$ mm, maximally mixed)

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    Cross section upper limits at 95% CL for the pair production of long-lived staus in the maximally mixed scenario, as...

  • Figure 8d ($c\tau_{0}=100$ mm, maximally mixed)

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    Cross section upper limits at 95% CL for the pair production of long-lived staus in the maximally mixed scenario, as...

  • Figure 8e ($c\tau_{0}=200$ mm, maximally mixed)

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    Cross section upper limits at 95% CL for the pair production of long-lived staus in the maximally mixed scenario, as...

  • Figure 8f ($c\tau_{0}=300$ mm, maximally mixed)

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    Cross section upper limits at 95% CL for the pair production of long-lived staus in the maximally mixed scenario, as...

  • Figure 9a ($c\tau_{0}=10$ mm, mass-degenerate)

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    Cross section upper limits at 95% CL for the pair production of long-lived staus in the mass-degenerate scenario, as a...

  • Figure 9b ($c\tau_{0}=30$ mm, mass-degenerate)

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    Cross section upper limits at 95% CL for the pair production of long-lived staus in the mass-degenerate scenario, as a...

  • Figure 9c ($c\tau_{0}=50$ mm, mass-degenerate)

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    Cross section upper limits at 95% CL for the pair production of long-lived staus in the mass-degenerate scenario, as a...

  • Figure 9d ($c\tau_{0}=100$ mm, mass-degenerate)

    10.17182/hepdata.166010.v1/t33

    Cross section upper limits at 95% CL for the pair production of long-lived staus in the mass-degenerate scenario, as a...

  • Figure 9e ($c\tau_{0}=200$ mm, mass-degenerate)

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    Cross section upper limits at 95% CL for the pair production of long-lived staus in the mass-degenerate scenario, as a...

  • Figure 9f ($c\tau_{0}=300$ mm, mass-degenerate)

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    Cross section upper limits at 95% CL for the pair production of long-lived staus in the mass-degenerate scenario, as a...

  • Theoretical cross sections for stau pair production

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    Theoretical cross sections at NLO+NLL accuracy for stau pair production.

  • Signal cutflows

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    Signal yields in the maximally mixed scenario for the BR selections, for a few representative sets of $(m_{\tilde{\tau}} [\text{GeV}], c\tau_{0}...

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