CMS-EXO-24-001

CMS-EXO-24-001 ; CERN-EP-2026-169
Search for dark matter in a signature with a four-prong large-radius jet in proton-proton collisions at $ \sqrt{s}= $ 13 TeV
CMS Collaboration
10 July 2026
Submitted to the Journal of High Energy Physics
Abstract: A search for a pair of nonprompt dark matter (DM) candidates produced in association with an initial-state radiation jet, in a signature containing a four-prong large-radius jet, is presented. The signal model contains a heavy vector or axial-vector mediator, which produces long-lived dark-sector particles that decay to a stable DM particle and a light boson, which decays to quarks. The analysis is based on data collected in the years 2016--2018 with the CMS detector at the LHC in proton-proton collisions at $ \sqrt{s}= $ 13 TeV, corresponding to an integrated luminosity of 138 fb$ ^{-1} $. Signal candidates feature large-radius jets, which are identified using a jet substructure tagger based on a graph neural network. The large-radius jet aims to reconstruct the decay of light DM mediators into four quarks, which are produced in association with two stable DM particles. The standard model background contributions are estimated from data using dedicated control regions. The missing transverse momentum spectrum is probed for a potential signal over the expected background. No significant excess over the standard model expectation is observed. Upper limits at 95% confidence level are set on the signal strength as functions of either the mediator mass or the relevant coupling. This is the first search for a pair of nonprompt DM candidates in the Lorentz-boosted topology, characterized by a large-radius jet and large missing transverse momentum.
Links: e-print arXiv:2607.11016 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ;

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Representative Feynman diagrams of the signal process. The mediator Y1 is produced via quark-antiquark annihilation (left) or gluon-gluon fusion (right) in association with a jet from initial-state radiation. A hatched circle represents an effective $ \mathrm{Y}_1 \mathrm{g} \mathrm{g} $ coupling.
png pdf	Figure 2: Distribution of $ s_{\text{GNN}} $ in the SR before imposing any requirement on $ s_{\text{GNN}} $ for the range of values considered in this analysis. The data are shown as black markers with vertical bars indicating the statistical uncertainty. Signal processes are shown as solid lines, while the total background, corresponding to the sum of all considered background contributions estimated from simulation, is represented by the filled histogram. The lower panel shows the ratio of the data and the total background prediction, and the hatched area represents the total uncertainty in the background. The different signal points shown in the figure are listed in Table 1. All distributions are normalized to unity.
png pdf	Figure 3: Postfit $ p_{\mathrm{T}}^\text{miss} $ distributions in the SR (upper left), QCD CR (upper right), $ \mathrm{W}+\text{jets} $ CR (lower left), and postfit distribution of the magnitude of the hadronic recoil in the $ \mathrm{Z}+\text{jets} $ CR (lower right). The data are shown as black markers with vertical bars indicating the statistical uncertainty. The SM expectation is shown as stacked histograms. In the SR, the prefit expected signal contributions are displayed as dashed lines for different signal parameter settings (different colors). In the middle panels, the ratio of the data to the postfit SM prediction is shown, with the total uncertainty in the latter represented as a hatched area. In the lower panels, the difference between data and SM expectation divided by the uncertainty in that difference (pull) is reported. The last bin includes the overflow events.
png pdf	Figure 3-a: Postfit $ p_{\mathrm{T}}^\text{miss} $ distributions in the SR (upper left), QCD CR (upper right), $ \mathrm{W}+\text{jets} $ CR (lower left), and postfit distribution of the magnitude of the hadronic recoil in the $ \mathrm{Z}+\text{jets} $ CR (lower right). The data are shown as black markers with vertical bars indicating the statistical uncertainty. The SM expectation is shown as stacked histograms. In the SR, the prefit expected signal contributions are displayed as dashed lines for different signal parameter settings (different colors). In the middle panels, the ratio of the data to the postfit SM prediction is shown, with the total uncertainty in the latter represented as a hatched area. In the lower panels, the difference between data and SM expectation divided by the uncertainty in that difference (pull) is reported. The last bin includes the overflow events.
png pdf	Figure 3-b: Postfit $ p_{\mathrm{T}}^\text{miss} $ distributions in the SR (upper left), QCD CR (upper right), $ \mathrm{W}+\text{jets} $ CR (lower left), and postfit distribution of the magnitude of the hadronic recoil in the $ \mathrm{Z}+\text{jets} $ CR (lower right). The data are shown as black markers with vertical bars indicating the statistical uncertainty. The SM expectation is shown as stacked histograms. In the SR, the prefit expected signal contributions are displayed as dashed lines for different signal parameter settings (different colors). In the middle panels, the ratio of the data to the postfit SM prediction is shown, with the total uncertainty in the latter represented as a hatched area. In the lower panels, the difference between data and SM expectation divided by the uncertainty in that difference (pull) is reported. The last bin includes the overflow events.
png pdf	Figure 3-c: Postfit $ p_{\mathrm{T}}^\text{miss} $ distributions in the SR (upper left), QCD CR (upper right), $ \mathrm{W}+\text{jets} $ CR (lower left), and postfit distribution of the magnitude of the hadronic recoil in the $ \mathrm{Z}+\text{jets} $ CR (lower right). The data are shown as black markers with vertical bars indicating the statistical uncertainty. The SM expectation is shown as stacked histograms. In the SR, the prefit expected signal contributions are displayed as dashed lines for different signal parameter settings (different colors). In the middle panels, the ratio of the data to the postfit SM prediction is shown, with the total uncertainty in the latter represented as a hatched area. In the lower panels, the difference between data and SM expectation divided by the uncertainty in that difference (pull) is reported. The last bin includes the overflow events.
png pdf	Figure 3-d: Postfit $ p_{\mathrm{T}}^\text{miss} $ distributions in the SR (upper left), QCD CR (upper right), $ \mathrm{W}+\text{jets} $ CR (lower left), and postfit distribution of the magnitude of the hadronic recoil in the $ \mathrm{Z}+\text{jets} $ CR (lower right). The data are shown as black markers with vertical bars indicating the statistical uncertainty. The SM expectation is shown as stacked histograms. In the SR, the prefit expected signal contributions are displayed as dashed lines for different signal parameter settings (different colors). In the middle panels, the ratio of the data to the postfit SM prediction is shown, with the total uncertainty in the latter represented as a hatched area. In the lower panels, the difference between data and SM expectation divided by the uncertainty in that difference (pull) is reported. The last bin includes the overflow events.
png pdf	Figure 4: Upper limits at 95% CL on the signal strength for different scenarios of the coupling $ g_{{\chi}{2} {\chi}{1} {Y}{0} } $ (left) and varying Y1 masses (right). The observed (expected) limits are shown as a solid (dashed) black line and the inner (green) band and the outer (yellow) band indicate the regions containing 68% and 95%, respectively, of the distribution of limits expected under the background-only hypothesis. The $ \sigma_{\text{theory}} $ values for the signal are reported in Table 1.
png pdf	Figure 4-a: Upper limits at 95% CL on the signal strength for different scenarios of the coupling $ g_{{\chi}{2} {\chi}{1} {Y}{0} } $ (left) and varying Y1 masses (right). The observed (expected) limits are shown as a solid (dashed) black line and the inner (green) band and the outer (yellow) band indicate the regions containing 68% and 95%, respectively, of the distribution of limits expected under the background-only hypothesis. The $ \sigma_{\text{theory}} $ values for the signal are reported in Table 1.
png pdf	Figure 4-b: Upper limits at 95% CL on the signal strength for different scenarios of the coupling $ g_{{\chi}{2} {\chi}{1} {Y}{0} } $ (left) and varying Y1 masses (right). The observed (expected) limits are shown as a solid (dashed) black line and the inner (green) band and the outer (yellow) band indicate the regions containing 68% and 95%, respectively, of the distribution of limits expected under the background-only hypothesis. The $ \sigma_{\text{theory}} $ values for the signal are reported in Table 1.

Tables
png pdf	Table 1: Combinations of particle masses and the $ g_{{\chi}{2} {\chi}{1} {Y}{0} } $ probed in this search. The configurations in the upper block vary the coupling $ g_{{\chi}{2} {\chi}{1} {Y}{0} } $ for fixed masses of the new particles, whereas the configurations in the lower block vary the Y1 boson mass for otherwise constant parameters. For all benchmark scenarios, the Y0 scalar mediator mass is fixed to $ m_{{Y}{0} }= $ 1 GeV. The quoted displacement $ L_{xy} $ corresponds to a characteristic transverse decay length. The theoretical cross sections for the benchmark scenarios are listed in the last column.
png pdf	Table 2: Tagger efficiency scale factors and absolute reconstruction efficiency derived for the representative signal parameters.
png pdf	Table 3: Summary of the systematic uncertainties considered in this analysis. The second column details whether the uncertainty affects the shape or the normalization (norm.) of the fitted distribution. Uncertainty in the third column reports the effect of a given uncertainty on the normalization of the affected processes.

Summary

The first search for a pair of nonprompt dark matter candidates in the Lorentz-boosted topology, characterized by a large-radius jet and large missing transverse momentum, has been presented. The analysis uses data collected in proton-proton collisions at $ \sqrt{s}= $ 13 TeV, corresponding to an integrated luminosity of 138 fb$^{-1}$. Signal candidates are selected by requiring the presence of a large-radius jet that is identified as signal-like using a tagger based on a graph neural network that exploits jet substructure and secondary vertex information. The dominant standard model backgrounds from quantum chromodynamics multijet production, $ \mathrm{Z}(\to\nu\nu)+\text{jets} $, and $ \mathrm{W}+\text{jets} $ processes are estimated from data using dedicated control regions. The missing transverse momentum spectrum is analyzed to search for a potential signal above the expected background. No significant excess over the standard model expectation is observed. Upper limits at 95% confidence level are set on the signal strength as functions of either the mediator mass or the coupling strength of the $ {\chi}{2} {\chi}{1} {Y}{0} $ vertex.

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