CMS-PAS-SUS-24-007

CMS-PAS-SUS-24-007
Search for dark matter produced in association with a Higgs boson decaying to bottom quarks in proton-proton collisions at $ \sqrt{s}= $ 13 TeV
CMS Collaboration
30 April 2025

Abstract: A search for dark matter produced in association with a Higgs boson decaying to a pair of bottom quarks is presented using data collected with the CMS detector in 2017 and 2018 at $ \sqrt{s}= $ 13 TeV, corresponding to an integrated luminosity of 101.3 fb$ ^{-1} $. The analysis is performed in exclusive channels targeting both boosted and resolved b quark pair topologies, covering a wide range of Higgs boson transverse momentum. The data are observed to agree with the SM predictions and limits on possible new physics are set in the framework of simplified benchmark models, 2HDM+a and Baryonic-Z'.
Links: CDS record (PDF) ; CADI line (restricted) ;

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Feynman diagrams for simplified benchmark models considered in this analysis: the 2HDM+a model (left) and Baryonic-Z' model (right).
png pdf	Figure 2: Comparison between observed data and background prediction in the SR before and after the simultaneous fit. The distributions are shown for boosted (upper) and resolved (lower) categories with the corresponding fitted observable, $ M_{\text{SD}} $ and $ M_{\text{bb}} $. The fit includes both categories, both data taking years and all signal and control regions. The signal predictions are overlaid as cyan and yellow color dashed lines, one for each benchmark model. The bottom panel shows the ratio of the observed data to pre-fit (maroon points) and post-fit (black points) background predictions, with the grey band indicating post-fit uncertainty obtained from combining all statistical and systematic sources. The data is observed to agree with the SM prediction with background-only hypothesis.
png pdf	Figure 2-a: Comparison between observed data and background prediction in the SR before and after the simultaneous fit. The distributions are shown for boosted (upper) and resolved (lower) categories with the corresponding fitted observable, $ M_{\text{SD}} $ and $ M_{\text{bb}} $. The fit includes both categories, both data taking years and all signal and control regions. The signal predictions are overlaid as cyan and yellow color dashed lines, one for each benchmark model. The bottom panel shows the ratio of the observed data to pre-fit (maroon points) and post-fit (black points) background predictions, with the grey band indicating post-fit uncertainty obtained from combining all statistical and systematic sources. The data is observed to agree with the SM prediction with background-only hypothesis.
png pdf	Figure 2-b: Comparison between observed data and background prediction in the SR before and after the simultaneous fit. The distributions are shown for boosted (upper) and resolved (lower) categories with the corresponding fitted observable, $ M_{\text{SD}} $ and $ M_{\text{bb}} $. The fit includes both categories, both data taking years and all signal and control regions. The signal predictions are overlaid as cyan and yellow color dashed lines, one for each benchmark model. The bottom panel shows the ratio of the observed data to pre-fit (maroon points) and post-fit (black points) background predictions, with the grey band indicating post-fit uncertainty obtained from combining all statistical and systematic sources. The data is observed to agree with the SM prediction with background-only hypothesis.
png pdf	Figure 3: Exclusion limits at 95% CL on the signal strength $ \mu $ for the 2HDM+a model as a function of the $ m_{\textrm{a}} $ (upper left), $ m_{\textrm{A}} $ (upper right), $ \sin\theta $ (lower left), and $ \tan\beta $ (lower right) parameters while the other model parameters are fixed to values indicated in the figures.
png	Figure 3-a: Exclusion limits at 95% CL on the signal strength $ \mu $ for the 2HDM+a model as a function of the $ m_{\textrm{a}} $ (upper left), $ m_{\textrm{A}} $ (upper right), $ \sin\theta $ (lower left), and $ \tan\beta $ (lower right) parameters while the other model parameters are fixed to values indicated in the figures.
png	Figure 3-b: Exclusion limits at 95% CL on the signal strength $ \mu $ for the 2HDM+a model as a function of the $ m_{\textrm{a}} $ (upper left), $ m_{\textrm{A}} $ (upper right), $ \sin\theta $ (lower left), and $ \tan\beta $ (lower right) parameters while the other model parameters are fixed to values indicated in the figures.
png	Figure 3-c: Exclusion limits at 95% CL on the signal strength $ \mu $ for the 2HDM+a model as a function of the $ m_{\textrm{a}} $ (upper left), $ m_{\textrm{A}} $ (upper right), $ \sin\theta $ (lower left), and $ \tan\beta $ (lower right) parameters while the other model parameters are fixed to values indicated in the figures.
png	Figure 3-d: Exclusion limits at 95% CL on the signal strength $ \mu $ for the 2HDM+a model as a function of the $ m_{\textrm{a}} $ (upper left), $ m_{\textrm{A}} $ (upper right), $ \sin\theta $ (lower left), and $ \tan\beta $ (lower right) parameters while the other model parameters are fixed to values indicated in the figures.
png pdf	Figure 4: Exclusion limits at 95% CL on the signal strength for the Baryonic-Z' model as a function of $ m_{\mathrm{Z}^{'}} $ and $ m_{\chi} $. The coupling parameters are fixed to $ g_{q} = $ 0.25 and $ g_{\chi} = $ 1. The result includes both categories and both data taking years. The region inside the black (red) contour corresponds to the observed (expected) exclusion. Mediator masses up to 2.1 (2.35) TeV are excluded for a DM mass of 1 GeV. The DM particle masses up to 500 GeV are excluded for a mediator mass of 1.25 TeV.

Tables
png pdf	Table 1: Boosted category signal and control region event selections applied in analysis. All events in all the analysis regions have a photon and tau candidate veto. Here "$ l $" refers to lepton (e or $ \mu $) depending on the control region, and "jets" refers to AK4 jets with $ \Delta R > $ 0.8 between the jet and the bb-tagged AK8 jet. "bjets" are "jets" that pass the DeepJet b-tag Loose WP.
png pdf	Table 2: Resolved category signal and control region event selections applied in analysis. All events in all the analysis regions have a photon and tau candidate veto. Here "$ l $" refers to lepton (e or $ \mu $) depending on the control region, and "jets" refers to AK4 jets with $ \Delta R > $ 0.4 between the jet and the leading and subleading b-tagged jets forming the Higgs candidate di-jet system.

Summary

A search for dark matter produced in association with a Higgs boson decaying to a pair of bottom quarks has been performed. The analysis is based on 101.3 fb$ ^{-1} $ of proton-proton collision data collected in 2017 and 2018 by the CMS experiment at $ \sqrt{s}= $ 13 TeV. The search has been performed in boosted and resolved categories to cover a wide range of Lorentz boost of the Higgs boson. The signal is extracted using a simultaneous fit to the signal and control regions by combining the two categories, and the 2017 and 2018 data sets. The observed data agrees with the SM predictions with a background-only fit, with no significant evidence for new physics. The results are interpreted in two simplified models, Baryonic-Z' and 2HDM+a, in which the exclusion limits are set on the model parameters at 95% CL. For Baryonic-Z', mediator Z' masses up to 2.1 TeV are excluded for DM mass of 1 GeV, and DM masses up to 500 GeV are excluded for 1.25 TeV Z'. In the 2HDM+a model, the light pseudoscalar masses $ m_{\textrm{a}} $ below 350 GeV are excluded for heavy pseudoscalar mass $ m_{\textrm{A}} $ of 1 TeV, and the $ m_{\textrm{A}} $ masses between 960 and 1300 GeV are excluded for $ m_{\textrm{a}} $ of 350 GeV. For other parameters, $ \sin\theta $ values between 0.16 and 0.93 are excluded, while the parameter space with $ \tan\beta $ values less than 4.0 is excluded.

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