CMS-PAS-EXO-23-002

CMS-PAS-EXO-23-002
Search for soft unclustered energy patterns in proton-proton collisions at 13 TeV
CMS Collaboration
5 December 2023

Abstract: The first dedicated search for soft unclustered energy patterns (SUEPs) is performed in proton-proton collisions at $ \sqrt{s}= $ 13 TeV, using data collected by the CMS detector at the LHC. SUEPs are predicted by Hidden Valley models that include a new, confining force with a large 't Hooft coupling and are characterized by a large multiplicity of low-momentum, diffuse, charged particles in the final state. The data, which correspond to a total integrated luminosity of 138 fb$ ^{-1} $, were collected in 2016-2018 using hadronic triggers, whose high energy thresholds preferentially select a boosted event topology. The track multiplicity and the sphericity of clustered tracks are used to discriminate against the large multijet background from standard model quantum chromodynamics interactions. No significant excess of events over the standard model expectation is observed. Limits are set on the production cross section of a scalar mediator produced via gluon fusion with SUEP-like decays.
Links: CDS record (PDF) ; CADI line (restricted) ; These preliminary results are superseded in this paper, Submitted to PRL. The superseded preliminary plots can be found here.

Figures	Summary	Additional Figures & Tables	References	CMS Publications

Figures
png pdf	Figure 1: The observed events as a function of the number of tracks in the SUEP candidate, for all CRs A--H and the SR. The pre-fit predicted background distribution is shown in the VR. Finally, the post-fit values for a background-only fit are shown for all regions and bins, except for the VR. The post-fit predictions for the F and SR bins with the highest $ n_{\text{constituent}}^{\text{SUEP}} $ range are 3.5 $ \times$ 10$^{-6}$ $\pm$ 8.4 $\times$ 10$^{-4} $ and 1.2 $ \times$ 10$^{-5}$ $\pm$ 2.9 $\times$ 10$^{-3} $, respectively.
png pdf	Figure 2: The 95% CL exclusion limits on the production cross section $ \sigma $ are shown as a function of $ m_{\text{S}} $ for various $ m_{\phi} $ and $ T_{\text{D}} $ values, and all decay modes.
png pdf	Figure 2-a: The 95% CL exclusion limits on the production cross section $ \sigma $ are shown as a function of $ m_{\text{S}} $ for various $ m_{\phi} $ and $ T_{\text{D}} $ values, and all decay modes.
png pdf	Figure 2-b: The 95% CL exclusion limits on the production cross section $ \sigma $ are shown as a function of $ m_{\text{S}} $ for various $ m_{\phi} $ and $ T_{\text{D}} $ values, and all decay modes.
png pdf	Figure 2-c: The 95% CL exclusion limits on the production cross section $ \sigma $ are shown as a function of $ m_{\text{S}} $ for various $ m_{\phi} $ and $ T_{\text{D}} $ values, and all decay modes.
png pdf	Figure 3: The 95% CL observed upper limits on the cross section shown as a function of $ T_{\text{D}} $ and the pseudoscalar mass $ m_{\phi} $ for $ m_{\text{S}} $ values of 125 GeV (left), 400 GeV (center), 1000 GeV (right), 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 $ \text{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	Figure 3-a: The 95% CL observed upper limits on the cross section shown as a function of $ T_{\text{D}} $ and the pseudoscalar mass $ m_{\phi} $ for $ m_{\text{S}} $ values of 125 GeV (left), 400 GeV (center), 1000 GeV (right), 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 $ \text{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	Figure 3-b: The 95% CL observed upper limits on the cross section shown as a function of $ T_{\text{D}} $ and the pseudoscalar mass $ m_{\phi} $ for $ m_{\text{S}} $ values of 125 GeV (left), 400 GeV (center), 1000 GeV (right), 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 $ \text{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	Figure 3-c: The 95% CL observed upper limits on the cross section shown as a function of $ T_{\text{D}} $ and the pseudoscalar mass $ m_{\phi} $ for $ m_{\text{S}} $ values of 125 GeV (left), 400 GeV (center), 1000 GeV (right), 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 $ \text{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	Figure 4: The observed and expected exclusions for the nominal $ \text{S} $ cross section for all $ m_{\text{S}} $ values, for the $ m_{\text{A}^{\prime}}= $ 1.0 GeV ($ \text{A}^{\prime} \rightarrow \pi^{+}\pi^{-} $ with $ \mathcal{B}= $ 100%) case, in a plane of $ m_{\phi} $ and $ T_{\text{D}} $. The regions below the lines are excluded.

Summary

This note presents the first search for soft unclustered energy patterns (SUEPs) at the LHC. 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 (ISR); the characteristic isotropic event shape of the SUEPs is recovered by boosting into the scalar mediator rest frame and removing the ISR particles. The number of tracks in the SUEP candidate is used to discriminate between the signal and the background from standard model quantum chromodynamics, which is estimated from data control regions. Stringent limits are placed on a hidden valley model for the most SUEP-like scenarios, where $ m_{\text{S}}/T_{\text{D}} \sim $ 100.

Additional Figures
png pdf	Additional Figure 1: The observed and expected exclusions for the nominal $ \text{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 a plane of $ m_{\phi} $ and $ T_{\text{D}} $. The regions below the lines are excluded.
png pdf	Additional Figure 2: The observed and expected exclusions for the nominal $ \text{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 a plane of $ m_{\phi} $ and $ T_{\text{D}} $. The regions below the lines are excluded.
png pdf	Additional Figure 3: An example signal event from a representative model with $ m_{\text{S}}= $ 800 GeV in the lab frame (left) and the generator-level $ \text{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.

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