CMS-SUS-23-013

CMS-SUS-23-013 ; CERN-EP-2026-087
Search for dark matter produced in association with a dark Higgs boson decaying into a bottom quark-antiquark pair in proton-proton collisions at $ \sqrt{s}= $ 13 TeV
CMS Collaboration
24 April 2026
Submitted to the European Physical Journal C
Abstract: A search for dark matter produced in association with a dark Higgs boson decaying into a bottom quark-antiquark pair has been performed using proton-proton collision data at a center-of-mass energy of 13 TeV. The search uses data collected with the CMS detector at the CERN LHC during the 2016--2018 data-taking period, corresponding to an integrated luminosity of 138 fb$ ^{-1} $. The results are interpreted in terms of a theoretical model of dark matter production that, together with a spin-1 gauge boson mediator, predicts the existence of a Higgs-boson-like particle in the dark sector (i.e., a dark Higgs boson). This search focuses on an experimental signature with large missing transverse momentum from dark matter production and a resonant structure in the invariant mass of the bottom quark-antiquark pair from the dark Higgs boson decay. Upper limits at 95% confidence level on the signal strength for dark Higgs boson mass hypotheses below 160 GeV are set. Values of the mediator mass up to 4.5 (2.5) TeV are excluded at 95% confidence level for a dark Higgs boson mass of 50 (150) GeV. This represents the most stringent limits set to date for the dark Higgs boson masses considered in this study.
Links: e-print arXiv:2604.20999 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ;

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Feynman diagram for the associated production of an $ \mathrm{H}_{\mathrm{D}} $ boson and $ \chi $ particles.
png pdf	Figure 2: Post-fit $ m_{\mathrm{SD}} $ distributions in bins of of the hadronic recoil $ U $. The upper panels present stacked post-fit predictions for the backgrounds superimposed on the data, with an example signal hypothesis overlaid. The lower panels show in red (blue) the pre-fit (post-fit) values of the ratio between the observed data and the predicted SM background, with their associated uncertainties. The gray area represents the total statistical post-fit uncertainty.
png pdf	Figure 3: Expected and observed exclusion limits at 95% CL on the signal strength $ \mu=\sigma/\sigma_\text{theory} $ as a function of the mediator mass $ m_{\mathrm{Z}^{'}} $ and dark matter mass $ m_\chi $ for six dark Higgs boson masses ($ \mathrm{H}_{\mathrm{D}} $ mass). Only scenarios with DM heavier than the $ \mathrm{H}_{\mathrm{D}} $ boson are considered. The black solid line indicates the observed exclusion boundary corresponding to $ \mu= $ 1. The black dashed and dotted lines represent the expected exclusion and the 68 and 95% CL intervals around the expected boundary, respectively. Parameter combinations corresponding to larger values of $ \mu $ are excluded.
png pdf	Figure 3-a: Expected and observed exclusion limits at 95% CL on the signal strength $ \mu=\sigma/\sigma_\text{theory} $ as a function of the mediator mass $ m_{\mathrm{Z}^{'}} $ and dark matter mass $ m_\chi $ for six dark Higgs boson masses ($ \mathrm{H}_{\mathrm{D}} $ mass). Only scenarios with DM heavier than the $ \mathrm{H}_{\mathrm{D}} $ boson are considered. The black solid line indicates the observed exclusion boundary corresponding to $ \mu= $ 1. The black dashed and dotted lines represent the expected exclusion and the 68 and 95% CL intervals around the expected boundary, respectively. Parameter combinations corresponding to larger values of $ \mu $ are excluded.
png pdf	Figure 3-b: Expected and observed exclusion limits at 95% CL on the signal strength $ \mu=\sigma/\sigma_\text{theory} $ as a function of the mediator mass $ m_{\mathrm{Z}^{'}} $ and dark matter mass $ m_\chi $ for six dark Higgs boson masses ($ \mathrm{H}_{\mathrm{D}} $ mass). Only scenarios with DM heavier than the $ \mathrm{H}_{\mathrm{D}} $ boson are considered. The black solid line indicates the observed exclusion boundary corresponding to $ \mu= $ 1. The black dashed and dotted lines represent the expected exclusion and the 68 and 95% CL intervals around the expected boundary, respectively. Parameter combinations corresponding to larger values of $ \mu $ are excluded.
png pdf	Figure 3-c: Expected and observed exclusion limits at 95% CL on the signal strength $ \mu=\sigma/\sigma_\text{theory} $ as a function of the mediator mass $ m_{\mathrm{Z}^{'}} $ and dark matter mass $ m_\chi $ for six dark Higgs boson masses ($ \mathrm{H}_{\mathrm{D}} $ mass). Only scenarios with DM heavier than the $ \mathrm{H}_{\mathrm{D}} $ boson are considered. The black solid line indicates the observed exclusion boundary corresponding to $ \mu= $ 1. The black dashed and dotted lines represent the expected exclusion and the 68 and 95% CL intervals around the expected boundary, respectively. Parameter combinations corresponding to larger values of $ \mu $ are excluded.
png pdf	Figure 3-d: Expected and observed exclusion limits at 95% CL on the signal strength $ \mu=\sigma/\sigma_\text{theory} $ as a function of the mediator mass $ m_{\mathrm{Z}^{'}} $ and dark matter mass $ m_\chi $ for six dark Higgs boson masses ($ \mathrm{H}_{\mathrm{D}} $ mass). Only scenarios with DM heavier than the $ \mathrm{H}_{\mathrm{D}} $ boson are considered. The black solid line indicates the observed exclusion boundary corresponding to $ \mu= $ 1. The black dashed and dotted lines represent the expected exclusion and the 68 and 95% CL intervals around the expected boundary, respectively. Parameter combinations corresponding to larger values of $ \mu $ are excluded.
png pdf	Figure 3-e: Expected and observed exclusion limits at 95% CL on the signal strength $ \mu=\sigma/\sigma_\text{theory} $ as a function of the mediator mass $ m_{\mathrm{Z}^{'}} $ and dark matter mass $ m_\chi $ for six dark Higgs boson masses ($ \mathrm{H}_{\mathrm{D}} $ mass). Only scenarios with DM heavier than the $ \mathrm{H}_{\mathrm{D}} $ boson are considered. The black solid line indicates the observed exclusion boundary corresponding to $ \mu= $ 1. The black dashed and dotted lines represent the expected exclusion and the 68 and 95% CL intervals around the expected boundary, respectively. Parameter combinations corresponding to larger values of $ \mu $ are excluded.
png pdf	Figure 3-f: Expected and observed exclusion limits at 95% CL on the signal strength $ \mu=\sigma/\sigma_\text{theory} $ as a function of the mediator mass $ m_{\mathrm{Z}^{'}} $ and dark matter mass $ m_\chi $ for six dark Higgs boson masses ($ \mathrm{H}_{\mathrm{D}} $ mass). Only scenarios with DM heavier than the $ \mathrm{H}_{\mathrm{D}} $ boson are considered. The black solid line indicates the observed exclusion boundary corresponding to $ \mu= $ 1. The black dashed and dotted lines represent the expected exclusion and the 68 and 95% CL intervals around the expected boundary, respectively. Parameter combinations corresponding to larger values of $ \mu $ are excluded.

Tables
png pdf	Table 1: Expected yields from background processes in the SR. The values shown are from Monte Carlo simulation, and the uncertainties are statistical only. The expected yields for a reference signal hypothesis with $ m_{\mathrm{Z}^{'}} = $ 1000 GeV, $ m_{\mathrm{H}_{\mathrm{D}}} = $ 130 GeV, and $ m_\chi = $ 150 GeV are also reported.
png pdf	Table 2: Summary of requirements that define the different analysis regions. A ``$\checkmark$'' means the requirement is enforced; a ``$ \times $'' means the variable is left unconstrained in that region (the requirement is not applied).
png pdf	Table 3: Summary of systematic uncertainties included in the analysis. The value given for each rate uncertainty is the maximum value before the fit is performed. Uncertainties in the shape of the distributions are instead labeled as such.

Summary

A search for dark matter (DM) produced in association with a dark Higgs boson ($ \mathrm{H}_{\mathrm{D}} $) in events with a resonant bottom quark-antiquark pair and large missing transverse momentum has been presented. Hypotheses for $ \mathrm{H}_{\mathrm{D}} $ bosons with masses between 50--150 GeV are tested with this search. Only scenarios in which the DM particle is more massive than the $ \mathrm{H}_{\mathrm{D}} $ boson are considered. A data set of proton-proton collisions at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of 138 fb$ ^{-1} $ is analyzed. A joint maximum likelihood fit spanning a set of one signal region and multiple control regions is used to constrain the standard model background contributions to the data and to extract a possible signal. No significant excess is observed above the background. The result is interpreted in terms of exclusion limits at 95% confidence level on the parameters of the model. Values of the mediator mass up to 4.5 (2.5) TeV are excluded for an $ \mathrm{H}_{\mathrm{D}} $ boson of 50 (150) GeV, assuming couplings of $ g_\mathrm{q} = $ 0.25 between the mediator and quarks, of $ g_\chi = $ 1.0 between the mediator and the DM particles, and a mixing angle between the $ \mathrm{H}_{\mathrm{D}} $ boson and the standard model Higgs boson of 0.01.

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