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| CMS-EXO-25-007 ; CERN-EP-2026-025 | ||
| Search for soft unclustered energy patterns produced in association with a W or Z boson in proton-proton collisions at $ \sqrt{s} = $ 13 TeV | ||
| CMS Collaboration | ||
| 7 April 2026 | ||
| Submitted to Physics Letters B | ||
| Abstract: A search for a Higgs boson produced in association with a W or Z boson and decaying via a soft unclustered energy pattern (SUEP) is presented. The analysis is based on proton-proton collision data corresponding to an integrated luminosity of 138 fb$^{-1}$ collected between 2016 and 2018 at the LHC. Final states with a leptonic W or Z boson decay associated with a high multiplicity of low-momentum charged particles are explored for the first time. The results show no significant excess over the standard model background expectation. Limits are set on the production cross section of a Higgs boson that decays to a SUEP, for a range of parameters of the SUEP model. Material is provided to facilitate further interpretation of the results. | ||
| Links: e-print arXiv:2604.05996 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ; | ||
| Figures | |
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Figure 1:
Schematic diagram of the 125 GeV Higgs boson decaying to a SUEP shower, produced in association with a leptonically decaying V boson. |
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Figure 2:
Distributions of $ n_{\text{constituent}}^{\text{SUEP}} $ in the extended ABCD subregions A--I in the PR-WH (upper) and PR-ZH (lower) regions, showing the observed data and the background predictions. The distribution is split into $ S^{\text{SUEP}}_{\text{boosted}} $ ($ p_{\mathrm{T}}^{\text{j}_{1}} $) bins for the WH (ZH) channel. The last $ n_{\text{constituent}}^{\text{SUEP}} $ bin includes the overflow events. The shaded bands indicate the uncertainties in the prediction, which are propagated to the ratios in the lower panels. |
png pdf |
Figure 2-a:
Distributions of $ n_{\text{constituent}}^{\text{SUEP}} $ in the extended ABCD subregions A--I in the PR-WH (upper) and PR-ZH (lower) regions, showing the observed data and the background predictions. The distribution is split into $ S^{\text{SUEP}}_{\text{boosted}} $ ($ p_{\mathrm{T}}^{\text{j}_{1}} $) bins for the WH (ZH) channel. The last $ n_{\text{constituent}}^{\text{SUEP}} $ bin includes the overflow events. The shaded bands indicate the uncertainties in the prediction, which are propagated to the ratios in the lower panels. |
png pdf |
Figure 2-b:
Distributions of $ n_{\text{constituent}}^{\text{SUEP}} $ in the extended ABCD subregions A--I in the PR-WH (upper) and PR-ZH (lower) regions, showing the observed data and the background predictions. The distribution is split into $ S^{\text{SUEP}}_{\text{boosted}} $ ($ p_{\mathrm{T}}^{\text{j}_{1}} $) bins for the WH (ZH) channel. The last $ n_{\text{constituent}}^{\text{SUEP}} $ bin includes the overflow events. The shaded bands indicate the uncertainties in the prediction, which are propagated to the ratios in the lower panels. |
png pdf |
Figure 3:
Distributions of $ n_{\text{constituent}}^{\text{SUEP}} $ in the extended ABCD subregions A--I in the SR for the WH (upper) and ZH (lower) channels, showing the observed data, the predictions from the background-only fit, and several signal hypotheses with fully hadronic decays ($ \mathcal{B}(A'\to\pi^{+}\pi^{-})=100% $): $ m_{\phi_{\text{D}}}=4 \text{GeV}, T_{\text{D}}= $ 8 GeV; $ m_{\phi_{\text{D}}}=3 \text{GeV}, T_{\text{D}}= $ 3 GeV; and $ m_{\phi_{\text{D}}}=4 \text{GeV}, T_{\text{D}}= $ 1 GeV. The distribution is split into $ S^{\text{SUEP}}_{\text{boosted}} $ ($ p_{\mathrm{T}}^{\text{j}_{1}} $) bins for the WH (ZH) channel. The last $ n_{\text{constituent}}^{\text{SUEP}} $ bin includes the overflow events. The shaded bands indicate the uncertainties in the prediction, which are propagated to the ratios in the lower panels. |
png pdf |
Figure 3-a:
Distributions of $ n_{\text{constituent}}^{\text{SUEP}} $ in the extended ABCD subregions A--I in the SR for the WH (upper) and ZH (lower) channels, showing the observed data, the predictions from the background-only fit, and several signal hypotheses with fully hadronic decays ($ \mathcal{B}(A'\to\pi^{+}\pi^{-})=100% $): $ m_{\phi_{\text{D}}}=4 \text{GeV}, T_{\text{D}}= $ 8 GeV; $ m_{\phi_{\text{D}}}=3 \text{GeV}, T_{\text{D}}= $ 3 GeV; and $ m_{\phi_{\text{D}}}=4 \text{GeV}, T_{\text{D}}= $ 1 GeV. The distribution is split into $ S^{\text{SUEP}}_{\text{boosted}} $ ($ p_{\mathrm{T}}^{\text{j}_{1}} $) bins for the WH (ZH) channel. The last $ n_{\text{constituent}}^{\text{SUEP}} $ bin includes the overflow events. The shaded bands indicate the uncertainties in the prediction, which are propagated to the ratios in the lower panels. |
png pdf |
Figure 3-b:
Distributions of $ n_{\text{constituent}}^{\text{SUEP}} $ in the extended ABCD subregions A--I in the SR for the WH (upper) and ZH (lower) channels, showing the observed data, the predictions from the background-only fit, and several signal hypotheses with fully hadronic decays ($ \mathcal{B}(A'\to\pi^{+}\pi^{-})=100% $): $ m_{\phi_{\text{D}}}=4 \text{GeV}, T_{\text{D}}= $ 8 GeV; $ m_{\phi_{\text{D}}}=3 \text{GeV}, T_{\text{D}}= $ 3 GeV; and $ m_{\phi_{\text{D}}}=4 \text{GeV}, T_{\text{D}}= $ 1 GeV. The distribution is split into $ S^{\text{SUEP}}_{\text{boosted}} $ ($ p_{\mathrm{T}}^{\text{j}_{1}} $) bins for the WH (ZH) channel. The last $ n_{\text{constituent}}^{\text{SUEP}} $ bin includes the overflow events. The shaded bands indicate the uncertainties in the prediction, which are propagated to the ratios in the lower panels. |
png pdf |
Figure 4:
Interpretation of the results for the decay of the 125 GeV Higgs boson mediator to a SUEP, for signal models with dominantly hadronic decays. The observed upper limit from the combination of the WH and ZH channels is shown as a function of the signal model parameters $ m_{\phi_{\text{D}}} $ and $ \log_{2}(T_{\text{D}}/m_{\phi_{\text{D}}}) $. The contours for each channel are drawn for a benchmark scenario in which the observed or expected upper limit for that channel on $ \sigma^{\text{prod}}\mathcal{B}(\mathrm{H}\to\text{SUEP})/\sigma^{\text{prod}}_{\text{SM}} $ equals 0.16. |
png pdf |
Figure 5:
Interpretation of the results for the decay of the 125 GeV Higgs boson mediator to a SUEP, for signal models with dominantly leptonic decays. The observed upper limit from the combination of the WH and ZH channels is shown as a function of the signal model parameters $ m_{\phi_{\text{D}}} $ and $ \log_{2}(T_{\text{D}}/m_{\phi_{\text{D}}}) $. The contours for each channel are drawn for a benchmark scenario in which the observed or expected upper limit for that channel on $ \sigma^{\text{prod}}\mathcal{B}(\mathrm{H}\to\text{SUEP})/\sigma^{\text{prod}}_{\text{SM}} $ equals 0.16. |
png pdf |
Figure 6:
Interpretation of the results for the decay of the 125 GeV Higgs boson mediator to a SUEP, for signal models with $ \mathcal{B}(A' \to\pi^{+}\pi^{-})=100% $. The observed upper limit from the combination of the WH and ZH channels is shown as a function of the signal model parameters $ m_{\phi_{\text{D}}} $ and $ \log_{2}(T_{\text{D}}/m_{\phi_{\text{D}}}) $. The contours for each channel are drawn for a benchmark scenario in which the observed or expected upper limit for that channel on $ \sigma^{\text{prod}}\mathcal{B}(\mathrm{H}\to\text{SUEP})/\sigma^{\text{prod}}_{\text{SM}} $ equals 0.16. |
png pdf |
Figure 7:
95% CL upper limits on the signal yield from the model-agnostic fit for different minimum $ n_{\text{constituent}}^{\text{SUEP}} $ values in the WH and ZH channels. |
| Summary |
| In summary, this Letter presents the first search for final states with a large-radius cluster of low-momentum, spherically distributed particles---a soft unclustered energy pattern or SUEP---and a massive vector boson. Events are selected at trigger level based on the presence of one or two charged leptons arising from the leptonic decays of the W or Z boson. This strategy improves significantly the sensitivity of the search to SUEP production via a Higgs boson mediator compared to previous results [14], with more significant improvements for signal models with higher multiplicities of low-momentum particles. Additional material is provided for full reinterpretation of the results using DELPHES and MADANALYSIS [60]. |
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