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| CMS-EXO-23-001 ; CERN-EP-2026-124 | ||
| Search for soft unclustered energy patterns in proton-proton collisions at $ \sqrt{s} = $ 13 TeV using data scouting | ||
| CMS Collaboration | ||
| 10 July 2026 | ||
| Submitted to Physical Review Letters | ||
| Abstract: A search for soft unclustered energy patterns (SUEPs) is conducted using proton-proton collision data corresponding to an integrated luminosity of 127 fb$^{-1}$ at a center-of-mass energy of 13 TeV, collected via the data scouting stream of the CMS experiment at the LHC. Only the results of the high-level trigger reconstruction are recorded to enable a lower threshold on the hadronic activity. This increases the acceptance for SUEP signatures, which are predicted by hidden-valley models with a large 't Hooft coupling. The observed results are consistent with the standard model background prediction. The most stringent limits to date are set on the gluon fusion production of heavy scalar mediators resulting in SUEP-like signals. | ||
| Links: e-print arXiv:2607.09621 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ; | ||
| Figures | |
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Figure 1:
A schematic diagram of the SUEP signal production with initial-state radiation. |
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Figure 2:
The observed $ n_{\text{constituent}}^{\text{SUEP}} $ distributions for various ranges of $ S^{\text{SUEP}}_{\text{boosted}} $ (left: 0.3 $ < S^{\text{SUEP}}_{\text{boosted}} < $ 0.34, middle: 0.34 $ < S^{\text{SUEP}}_{\text{boosted}} < $ 0.5, right: $ S^{\text{SUEP}}_{\text{boosted}} > $ 0.5), compared to the background prediction in the SR. The pre-fit expected background from Eq. \eqrefeq:extended-ABCD, the background-only fit result, and two signal models with $ m_{\text{S}} = $ 300 and 1000 GeV are shown, as well as their uncertainties. Both signal models have $ T_{\text{D}} = m_{\phi} = $ 3 GeV and $ m_{{A}{\prime} } = $ 1 GeV (fully hadronic decays). The vertical dashed lines mark the boundaries that separate the CRs, the VR, and the SR. The lower panels show the ratio of data to the post-fit background prediction. |
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Figure 3:
The observed $ n_{\text{constituent}}^{\text{SUEP}} $ distributions for various ranges of $ S^{\text{SUEP}}_{\text{boosted}} $ (left: 0.3 $ < S^{\text{SUEP}}_{\text{boosted}} < $ 0.34, middle: 0.34 $ < S^{\text{SUEP}}_{\text{boosted}} < $ 0.5, right: $ S^{\text{SUEP}}_{\text{boosted}} > $ 0.5), compared to the background prediction in the SR. The pre-fit expected background from Eq. \eqrefeq:extended-ABCD, the background-only fit result, and two signal models with $ m_{\text{S}} = $ 300 and 1000 GeV are shown, as well as their uncertainties. Both signal models have $ T_{\text{D}} = m_{\phi} = $ 3 GeV and $ m_{{A}{\prime} } = $ 1 GeV (fully hadronic decays). The vertical dashed lines mark the boundaries that separate the CRs, the VR, and the SR. The lower panels show the ratio of data to the post-fit background prediction. |
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Figure 4:
Expected and observed 95% CL upper limits on the simplified scalar-mediator SUEP cross sections as functions of the mediator mass $ m_{\text{S}} $, with a comparison to the corresponding limits from the previous CMS offline search [32]. Signal models with different values of the temperature, dark hadron mass, and dark photon mass are shown. Upper left: $ T_{\text{D}} = m_{\phi} = $ 2 GeV, $ m_{{A}{\prime} } = $ 1 GeV (fully hadronic decays). Upper right: $ T_{\text{D}} = m_{\phi} = $ 4 GeV, $ m_{{A}{\prime} } = $ 0.5 GeV (lepton-dominated decays). Lower: $ T_{\text{D}} = m_{\phi} = $ 8 GeV, $ m_{{A}{\prime} } = $ 0.7 GeV (hadron-dominated decays). |
png pdf |
Figure 4-a:
Expected and observed 95% CL upper limits on the simplified scalar-mediator SUEP cross sections as functions of the mediator mass $ m_{\text{S}} $, with a comparison to the corresponding limits from the previous CMS offline search [32]. Signal models with different values of the temperature, dark hadron mass, and dark photon mass are shown. Upper left: $ T_{\text{D}} = m_{\phi} = $ 2 GeV, $ m_{{A}{\prime} } = $ 1 GeV (fully hadronic decays). Upper right: $ T_{\text{D}} = m_{\phi} = $ 4 GeV, $ m_{{A}{\prime} } = $ 0.5 GeV (lepton-dominated decays). Lower: $ T_{\text{D}} = m_{\phi} = $ 8 GeV, $ m_{{A}{\prime} } = $ 0.7 GeV (hadron-dominated decays). |
png pdf |
Figure 4-b:
Expected and observed 95% CL upper limits on the simplified scalar-mediator SUEP cross sections as functions of the mediator mass $ m_{\text{S}} $, with a comparison to the corresponding limits from the previous CMS offline search [32]. Signal models with different values of the temperature, dark hadron mass, and dark photon mass are shown. Upper left: $ T_{\text{D}} = m_{\phi} = $ 2 GeV, $ m_{{A}{\prime} } = $ 1 GeV (fully hadronic decays). Upper right: $ T_{\text{D}} = m_{\phi} = $ 4 GeV, $ m_{{A}{\prime} } = $ 0.5 GeV (lepton-dominated decays). Lower: $ T_{\text{D}} = m_{\phi} = $ 8 GeV, $ m_{{A}{\prime} } = $ 0.7 GeV (hadron-dominated decays). |
png pdf |
Figure 4-c:
Expected and observed 95% CL upper limits on the simplified scalar-mediator SUEP cross sections as functions of the mediator mass $ m_{\text{S}} $, with a comparison to the corresponding limits from the previous CMS offline search [32]. Signal models with different values of the temperature, dark hadron mass, and dark photon mass are shown. Upper left: $ T_{\text{D}} = m_{\phi} = $ 2 GeV, $ m_{{A}{\prime} } = $ 1 GeV (fully hadronic decays). Upper right: $ T_{\text{D}} = m_{\phi} = $ 4 GeV, $ m_{{A}{\prime} } = $ 0.5 GeV (lepton-dominated decays). Lower: $ T_{\text{D}} = m_{\phi} = $ 8 GeV, $ m_{{A}{\prime} } = $ 0.7 GeV (hadron-dominated decays). |
png pdf |
Figure 5:
Expected and observed 95% CL exclusion limits in the $ (T_{\text{D}},m_{\phi}) $ plane, assuming ggF production of scalar mediators $ \text{S} $ with the nominal cross sections and $ m_{{A}{\prime} } = $ 1 GeV (fully hadronic decays). The region below each curve is excluded for that signal model. |
png pdf |
Figure 6:
The $ n_{\text{constituent}}^{\text{SUEP}} $ distributions for various ranges of $ S^{\text{SUEP}}_{\text{boosted}} $ (left: 0.3 $ < S^{\text{SUEP}}_{\text{boosted}} < $ 0.34, middle: 0.34 $ < S^{\text{SUEP}}_{\text{boosted}} < $ 0.5, right: $ S^{\text{SUEP}}_{\text{boosted}} \geq $ 0.5) in QCD multijet simulation, comparing the extended ABCD prediction to the yield directly from the simulation in the SR. The pre-fit expected background from Eq. \eqrefeq:extended-ABCD, the background-only fit results, and two signal models with $ m_{\text{S}} = $ 300 and 1000 GeV are shown, as well as their uncertainties. Both signal models have $ T_{\text{D}} = m_{\phi} = $ 3 GeV and $ m_{{A}{\prime} } = $ 1 GeV (fully hadronic decays). The vertical dashed lines mark the boundaries that separate the CRs, the VR, and the SR. Simulated samples corresponding to the 2017 and 2018 data-taking conditions are used. The lower panels show the ratio of data to the post-fit background prediction. |
png pdf |
Figure 7:
Validation of the extended ABCD method (left: 2016, middle: 2017, right: 2018) in the VR, where signal is negligible compared to background, as shown for signal models with $ m_{\text{S}} = 125, 400\text{, and} $ 1000 GeV, $ T_{\text{D}} = m_{\phi} = $ 3 GeV, and $ m_{{A}{\prime} } = $ 1 GeV (fully hadronic decays). The lower panels show the ratio of data to the expected background in the VR. |
png pdf |
Figure 7-a:
Validation of the extended ABCD method (left: 2016, middle: 2017, right: 2018) in the VR, where signal is negligible compared to background, as shown for signal models with $ m_{\text{S}} = 125, 400\text{, and} $ 1000 GeV, $ T_{\text{D}} = m_{\phi} = $ 3 GeV, and $ m_{{A}{\prime} } = $ 1 GeV (fully hadronic decays). The lower panels show the ratio of data to the expected background in the VR. |
png pdf |
Figure 7-b:
Validation of the extended ABCD method (left: 2016, middle: 2017, right: 2018) in the VR, where signal is negligible compared to background, as shown for signal models with $ m_{\text{S}} = 125, 400\text{, and} $ 1000 GeV, $ T_{\text{D}} = m_{\phi} = $ 3 GeV, and $ m_{{A}{\prime} } = $ 1 GeV (fully hadronic decays). The lower panels show the ratio of data to the expected background in the VR. |
png pdf |
Figure 7-c:
Validation of the extended ABCD method (left: 2016, middle: 2017, right: 2018) in the VR, where signal is negligible compared to background, as shown for signal models with $ m_{\text{S}} = 125, 400\text{, and} $ 1000 GeV, $ T_{\text{D}} = m_{\phi} = $ 3 GeV, and $ m_{{A}{\prime} } = $ 1 GeV (fully hadronic decays). The lower panels show the ratio of data to the expected background in the VR. |
| Summary |
| In summary, a search has been reported for soft unclustered energy patterns (SUEPs) at the LHC using scouting proton-proton collision data at $ \sqrt{s} = $ 13 TeV, corresponding to an integrated luminosity of 127 fb$^{-1}$. This data set is recorded by a high-level trigger with a lower threshold on the scalar sum ($H_T$) of jet transverse momenta ($p_T$) compared to the standard $H_T$ triggers, offsetting the increase in rate by saving limited event content. The characteristic isotropic event shape of SUEP signals is recovered by analyzing the jet in the SUEP-candidate rest frame and selecting particles from only the SUEP candidate, which is chosen as the jet with the highest constituent multiplicity out of the two highest $p_T$ large-radius jets. The standard model background from quantum chromodynamics multijet processes is estimated from data control regions. The search sets the most stringent limits on a large range of SUEP models with a temperature and dark-hadron mass around a few GeV, and scalar mediator masses above 125 GeV. |
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