CMS-EXO-23-002

CMS-EXO-23-002 ; CERN-EP-2024-054
Search for soft unclustered energy patterns in proton-proton collisions at 13 TeV
CMS Collaboration
8 March 2024
Accepted for publication in Phys. Rev. Lett.
Abstract: The first search for soft unclustered energy patterns (SUEPs) is performed using an integrated luminosity of 138 fb$ ^{-1} $ of proton-proton collision data at $ \sqrt{s}= $ 13 TeV, collected in 2016-2018 by the CMS detector at the LHC. Such SUEPs are predicted by Hidden Valley models with a new, confining force with a large 't Hooft coupling. In events with boosted topologies, selected by high-threshold hadronic triggers, the multiplicity and sphericity of clustered tracks are used to reject the background from standard model quantum chromodynamics. With no observed excess of events over the standard model expectation, limits are set on the cross section for production via gluon fusion of a scalar mediator with SUEP-like decays.
Links: e-print arXiv:2403.05311 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; Physics Briefing ; CADI line (restricted) ;

Figures	Summary	Additional Figures & Tables	References	CMS Publications

Figures
png pdf	Figure 1: A schematic Feynman diagram of the benchmark signal model resulting in a SUEP signature.
png pdf	Figure 2: The number of observed events as a function of the number of tracks in the SUEP candidate, for all CRs A-H and the SR, as well as two signal samples. The three figures correspond to contiguous $ S^{\text{SUEP}}_{\text{boosted}} $ ranges. The pre-fit predicted background distribution is shown in the VR, the first bin of the SR. For all other regions and bins, the post-fit values for a background-only fit are shown.
png pdf	Figure 3: The 95% CL exclusion limits on the production cross section $ \sigma $ are shown as a function of $ m_{\text{S}} $ for $ m_{\phi} = T_{\text{D}} = $ 3 GeV, for all decay modes.
png pdf	Figure 4: The observed and expected exclusions for the nominal $ \text{S} $ cross section in the plane of $ m_{\phi} $ and $ T_{\text{D}} $, for various $ m_{\text{S}} $ values, for the case $ m_{{\mathrm{A}'}}= $ 1.0 GeV ($ {\mathrm{A}'} \to \pi^{+}\pi^{-} $ with $ \mathcal{B}= $ 100%). The regions below the observed limits are excluded.

Summary

In summary, this Letter presents the first search for soft unclustered energy patterns (SUEPs). Data corresponding to an integrated luminosity of 138 fb$ ^{-1} $ are used, collected with a trigger requiring a high scalar sum of jet transverse momenta and reconstructed with the full offline processing. This strategy preferentially selects events with initial-state radiation; the characteristic isotropic event shape of the SUEPs is recovered by boosting into the scalar mediator rest frame and removing the initial-state radiation particles. The number of tracks and the associated sphericity in the SUEP candidate are used to discriminate between the signal and the background from standard model quantum chromodynamics, which is estimated from data in suitable control regions. Stringent limits are placed on the most SUEP-like Hidden Valley scenarios with highly isotropic dark showers producing a large multiplicity of tracks.

Additional Figures
png pdf	Additional Figure 1: The 95% CL exclusion limits on the production cross section $ \sigma $ as a functions of $ m_{\text{S}} $ for various $ m_{\phi} $ and $ T_{\text{D}} $ values and all decay modes.
png pdf	Additional Figure 1-a: The 95% CL exclusion limits on the production cross section $ \sigma $ as a functions of $ m_{\text{S}} $ for various $ m_{\phi} $ and $ T_{\text{D}} $ values and all decay modes.
png pdf	Additional Figure 1-b: The 95% CL exclusion limits on the production cross section $ \sigma $ as a functions of $ m_{\text{S}} $ for various $ m_{\phi} $ and $ T_{\text{D}} $ values and all decay modes.
png pdf	Additional Figure 2: The 95% CL observed upper limits on the cross section as a function of $ T_{\text{D}} $ and the pseudoscalar mass $ m_{\phi} $ for $ m_{\text{S}} $ values of 300 GeV (upper), 600 GeV (middle), and 1000 GeV (lower), in the $ m_{\text{A}^{\prime}}= $ 1.0 GeV ($ \text{A}^{\prime} \to \pi^{+}\pi^{-} $ with $ \mathcal{B}=$ 100%) case. The solid dark blue curves indicate the observed exclusions for the nominal S cross section, while the dashed red curves indicate the expected exclusions, and the dashed light blue curves indicate the region containing 68% of the distributions of expected exclusions. The regions below the lines are excluded.
png pdf	Additional Figure 2-a: The 95% CL observed upper limits on the cross section as a function of $ T_{\text{D}} $ and the pseudoscalar mass $ m_{\phi} $ for $ m_{\text{S}} $ values of 300 GeV (upper), 600 GeV (middle), and 1000 GeV (lower), in the $ m_{\text{A}^{\prime}}= $ 1.0 GeV ($ \text{A}^{\prime} \to \pi^{+}\pi^{-} $ with $ \mathcal{B}=$ 100%) case. The solid dark blue curves indicate the observed exclusions for the nominal S cross section, while the dashed red curves indicate the expected exclusions, and the dashed light blue curves indicate the region containing 68% of the distributions of expected exclusions. The regions below the lines are excluded.
png pdf	Additional Figure 2-b: The 95% CL observed upper limits on the cross section as a function of $ T_{\text{D}} $ and the pseudoscalar mass $ m_{\phi} $ for $ m_{\text{S}} $ values of 300 GeV (upper), 600 GeV (middle), and 1000 GeV (lower), in the $ m_{\text{A}^{\prime}}= $ 1.0 GeV ($ \text{A}^{\prime} \to \pi^{+}\pi^{-} $ with $ \mathcal{B}=$ 100%) case. The solid dark blue curves indicate the observed exclusions for the nominal S cross section, while the dashed red curves indicate the expected exclusions, and the dashed light blue curves indicate the region containing 68% of the distributions of expected exclusions. The regions below the lines are excluded.
png pdf	Additional Figure 2-c: The 95% CL observed upper limits on the cross section as a function of $ T_{\text{D}} $ and the pseudoscalar mass $ m_{\phi} $ for $ m_{\text{S}} $ values of 300 GeV (upper), 600 GeV (middle), and 1000 GeV (lower), in the $ m_{\text{A}^{\prime}}= $ 1.0 GeV ($ \text{A}^{\prime} \to \pi^{+}\pi^{-} $ with $ \mathcal{B}=$ 100%) case. The solid dark blue curves indicate the observed exclusions for the nominal S cross section, while the dashed red curves indicate the expected exclusions, and the dashed light blue curves indicate the region containing 68% of the distributions of expected exclusions. The regions below the lines are excluded.
png pdf	Additional Figure 3: The observed and expected exclusions for the nominal S cross section for all $ m_{\text{S}} $ values, for the $ m_{\text{A}^{\prime}} = $ 0.5 GeV ($ \text{A}^{\prime} \to \mathrm{e}^+\mathrm{e}^-, \mu^{+}\mu^{-}, \pi^{+}\pi^{-} $ with $ \mathcal{B} = $ 40, 40, 20%) case, in the plane of $ m_{\phi} $ and $ T_{\text{D}} $. The regions below the lines are excluded.
png pdf	Additional Figure 4: The observed and expected exclusions for the nominal S cross section for all $ m_{\text{S}} $ values, for the $ m_{\text{A}^{\prime}} = $ 0.7 GeV ($ \text{A}^{\prime} \to \mathrm{e}^+\mathrm{e}^-, \mu^{+}\mu^{-}, \pi^{+}\pi^{-} $ with $ \mathcal{B} = $ 15, 15, 70%) case, in the plane of $ m_{\phi} $ and $ T_{\text{D}} $. The regions below the lines are excluded.
png pdf	Additional Figure 5: An example signal event from a representative model with $ m_{\text{S}}= $ 800 GeV in the lab frame (left) and the generator-level S mediator frame (right). The jets are clustered from charged particle tracks associated with the primary vertex using the anti-$ k_{\mathrm{T}} $ algorithm with $ R= $ 1.5. The size of each dot is scaled based on the $ p_{\mathrm{T}} $ of the corresponding track.

Additional Tables
png pdf	Additional Table 1: The observed and predicted yields in the SR, applying the extended ABCD method to the ISR candidate. Only statistical uncertainties are shown. The deviation of the ratio from unity, averaged across all years, is taken as a systematic uncertainty in the final SR prediction to address higher-order correlations between the variables used in the extended ABCD method.
png pdf	Additional Table 2: The observed and predicted yields in the VR, which corresponds to the first bin in the SR, applying the extended ABCD method to the SUEP candidate. The statistical and systematic uncertainties are shown separately. (The VR is not used in the final fit.)
png pdf	Additional Table 3: The numbers of observed and predicted (post-fit) events for each SR bin.
png pdf	Additional Table 4: For a selection of signal samples in era 2018 with $ m_{\phi} = T_{\text{D}} = $ 3 GeV, the relative efficiencies and the total efficiency with respect to the selection on the generator-level $ H_{\mathrm{T}} $, $ H_{\text{T}}^{\text{gen}} > $ 1000 GeV.

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