CMS-PAS-SUS-21-005

CMS-PAS-SUS-21-005
Search for new physics using single-lepton events with high jet and b jet multiplicities in proton-proton collisions at $ \sqrt{s}= $ 13 TeV
CMS Collaboration
2025-07-14

Abstract: This note presents a search for new physics using single-lepton events with high multiplicity of jets and b-tagged jets, without a requirement on missing transverse momentum. The analysis is based on proton-proton collision data collected with the CMS detector at the CERN LHC at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb$ ^{-1} $. It is sensitive to $ R $-parity violating supersymmetry models, where supersymmetric particles can decay into standard model particles through interactions that violate baryon number conservation. In particular, the target model is gluino pair production where each gluino decays to top, bottom, and strange quarks. The sum of large-radius jet masses is used to distinguish the signal from background. No significant excess over the background is observed, and constraints are placed on the parameter space of gluino mass. Such gluinos with a mass of 1890 GeV are excluded at 95% confidence level.
Links: CDS record (PDF) ; CADI line (restricted) ;

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Diagram of the signal model considered in this analysis. Gluinos are produced in pairs and decay to top (t), bottom (b), and strange (s) quarks.
png pdf	Figure 2: Distributions of $ N_{\textrm{jet}} $ (left), $ N_{\textrm{b}} $ (middle), and $ M_{\textrm{J}} $ (right) for $ {\mathrm{t}\overline{\mathrm{t}}} $ and signal events with two gluino mass scenarios, after applying the baseline selection, as described in Section 3.
png pdf	Figure 2-a: Distributions of $ N_{\textrm{jet}} $ (left), $ N_{\textrm{b}} $ (middle), and $ M_{\textrm{J}} $ (right) for $ {\mathrm{t}\overline{\mathrm{t}}} $ and signal events with two gluino mass scenarios, after applying the baseline selection, as described in Section 3.
png pdf	Figure 2-b: Distributions of $ N_{\textrm{jet}} $ (left), $ N_{\textrm{b}} $ (middle), and $ M_{\textrm{J}} $ (right) for $ {\mathrm{t}\overline{\mathrm{t}}} $ and signal events with two gluino mass scenarios, after applying the baseline selection, as described in Section 3.
png pdf	Figure 2-c: Distributions of $ N_{\textrm{jet}} $ (left), $ N_{\textrm{b}} $ (middle), and $ M_{\textrm{J}} $ (right) for $ {\mathrm{t}\overline{\mathrm{t}}} $ and signal events with two gluino mass scenarios, after applying the baseline selection, as described in Section 3.
png pdf	Figure 3: Comparison of $ M_{\textrm{J}} $ templates between data and MC in the control regions used to measure the $ \kappa $ factors for QCD (left), $ \mathrm{W}+ $jets (middle), and $ {\mathrm{t}\overline{\mathrm{t}}} $ (right). The selection corresponds to $ N_{\textrm{lep}}= $ 0, $ N_{\textrm{jet}}\ge $ 9, $ N_{\textrm{b}}= $ 0 for QCD; a Drell-Yan-dominated region with $ N_{\textrm{lep}}= $ 2, $ N_{\textrm{jet}}\ge $ 7, $ N_{\textrm{b}}\le $ 0 for $ \mathrm{W}+ $jets; and $ N_{\textrm{lep}}= $ 1, $ N_{\textrm{jet}}\ge $ 8, $ N_{\textrm{b}}= $ 1 for $ {\mathrm{t}\overline{\mathrm{t}}} $. The MC is normalized to data in all regions.
png pdf	Figure 3-a: Comparison of $ M_{\textrm{J}} $ templates between data and MC in the control regions used to measure the $ \kappa $ factors for QCD (left), $ \mathrm{W}+ $jets (middle), and $ {\mathrm{t}\overline{\mathrm{t}}} $ (right). The selection corresponds to $ N_{\textrm{lep}}= $ 0, $ N_{\textrm{jet}}\ge $ 9, $ N_{\textrm{b}}= $ 0 for QCD; a Drell-Yan-dominated region with $ N_{\textrm{lep}}= $ 2, $ N_{\textrm{jet}}\ge $ 7, $ N_{\textrm{b}}\le $ 0 for $ \mathrm{W}+ $jets; and $ N_{\textrm{lep}}= $ 1, $ N_{\textrm{jet}}\ge $ 8, $ N_{\textrm{b}}= $ 1 for $ {\mathrm{t}\overline{\mathrm{t}}} $. The MC is normalized to data in all regions.
png pdf	Figure 3-b: Comparison of $ M_{\textrm{J}} $ templates between data and MC in the control regions used to measure the $ \kappa $ factors for QCD (left), $ \mathrm{W}+ $jets (middle), and $ {\mathrm{t}\overline{\mathrm{t}}} $ (right). The selection corresponds to $ N_{\textrm{lep}}= $ 0, $ N_{\textrm{jet}}\ge $ 9, $ N_{\textrm{b}}= $ 0 for QCD; a Drell-Yan-dominated region with $ N_{\textrm{lep}}= $ 2, $ N_{\textrm{jet}}\ge $ 7, $ N_{\textrm{b}}\le $ 0 for $ \mathrm{W}+ $jets; and $ N_{\textrm{lep}}= $ 1, $ N_{\textrm{jet}}\ge $ 8, $ N_{\textrm{b}}= $ 1 for $ {\mathrm{t}\overline{\mathrm{t}}} $. The MC is normalized to data in all regions.
png pdf	Figure 3-c: Comparison of $ M_{\textrm{J}} $ templates between data and MC in the control regions used to measure the $ \kappa $ factors for QCD (left), $ \mathrm{W}+ $jets (middle), and $ {\mathrm{t}\overline{\mathrm{t}}} $ (right). The selection corresponds to $ N_{\textrm{lep}}= $ 0, $ N_{\textrm{jet}}\ge $ 9, $ N_{\textrm{b}}= $ 0 for QCD; a Drell-Yan-dominated region with $ N_{\textrm{lep}}= $ 2, $ N_{\textrm{jet}}\ge $ 7, $ N_{\textrm{b}}\le $ 0 for $ \mathrm{W}+ $jets; and $ N_{\textrm{lep}}= $ 1, $ N_{\textrm{jet}}\ge $ 8, $ N_{\textrm{b}}= $ 1 for $ {\mathrm{t}\overline{\mathrm{t}}} $. The MC is normalized to data in all regions.
png pdf	Figure 4: $ \kappa $ factors measured in control regions for QCD (yellow), $ \mathrm{W}+ $jets (purple), and $ {\mathrm{t}\overline{\mathrm{t}}} $ (blue). The top and bottom corresponds to $ \kappa_1 $ and $ \kappa_2 $, respectively. In each case, the three points indicate the $ \kappa $ values in each $ N_{\textrm{jet}} $ bin. The error bars include the statistical uncertainties of data (dominant) and MC samples.
png pdf	Figure 5: Post-fit $ M_{\textrm{J}} $ distributions in the $ N_{\textrm{lep}}= $ 1 region for all three years. The three $ M_{\textrm{J}} $ bins used, defined as 500 $ < M_{\textrm{J}} < $ 800, 800 $ < M_{\textrm{J}} < $ 1100, and $ M_{\textrm{J}} > 1100 \,\text{Ge\hspace{-.08em}V} $, are shown from left to right. The data-to-MC ratio is shown in the lower panel, where the gray band represents the total (statistical and systematic) uncertainty in the background prediction.
png pdf	Figure 6: Cross section upper limits at 95% CL compared to the gluino pair production with $ \mathrm{\widetilde{g}} \rightarrow \mathrm{t} \mathrm{b} \mathrm{s} $ (magenta). The theoretical uncertainties in the cross section are represented by the dotted band. The expected limits are shown by the black dashed line, with $ \pm $1$\sigma $ and $ \pm $2$\sigma $ variations indicated by the green and yellow bands, respectively. The observed limit is shown as a black solid line with dots.

Tables
png pdf	Table 1: A diagram representing the analysis regions after the baseline selection. ``CR'' denotes a control region and ``SR'' denotes a signal region. Yellow indicates regions where the $ M_{\textrm{J}} $ template is used, while lighter yellow corresponds to regions where it is not used.
png pdf	Table 2: Selection criteria applied for measuring the $ \kappa $ factors of the main backgrounds.
png pdf	Table 3: Uncertainties of $ \kappa $ factors for QCD, $ \mathrm{W}+ $jets, and $ {\mathrm{t}\overline{\mathrm{t}}} $ backgrounds in the three $ N_{\textrm{jet}} $ regions, used in the global fit.
png pdf	Table 4: List of signal systematic uncertainties and their effects on the yields in the $ N_{\textrm{jet}}\ge $ 8 and $ N_{\textrm{b}}\ge $ 4 bin for the all three years combined. The signal corresponds to $ m_{\mathrm{\widetilde{g}}}= $ 1800 GeV.
png pdf	Table 5: Post-fit yields in the signal region for all three years combined.

Summary

This analysis investigates the existence of physics beyond the standard model in events characterized by high jet and b-jet multiplicities in the single-lepton final state, without a requirement on missing transverse momentum. The scalar sum of the large-radius jet masses ($ M_{\textrm{J}} $) in an event is used for both background rejection and prediction, and a simultaneous fit to the $ M_{\textrm{J}} $ templates, in bins of jet multiplicity $ N_{\textrm{jet}} $ and the number of b-tagged jets $ N_{\textrm{b}} $, is performed to extract potential excesses in data. The templates, derived from simulation, are corrected by measurements comparing data and simulation in dedicated control regions. This method enables a data-driven prediction of background across bins of $ N_{\textrm{jet}} $, $ N_{\textrm{b}} $, and $ M_{\textrm{J}} $. The observed event yields are consistent with background predictions. The result is interpreted within the framework of $ R $-parity violating Supersymmetry under the minimal flavor violating scenario. The search focuses on gluino pair production, where each gluino decays to a top, a bottom, and a strange quark via the $ \lambda^{\prime\prime}_{332} $ coupling. Using proton-proton collisions at $ \sqrt{s} = $ 13 TeV from the CERN LHC collected by the CMS experiment between 2016 to 2018 and corresponding to an integrated luminosity of 138 fb$ ^{-1} $, gluinos are excluded up to a mass of 1890 GeV at 95% confidence level.

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