CMS-PAS-EXO-24-001

CMS-PAS-EXO-24-001
Search for dark matter produced in association with a boosted large-radius jet in proton-proton collisions at $ \sqrt{s}= $ 13 TeV
CMS Collaboration
2026-03-18

Abstract: A search for a displaced dark matter candidate produced in association with a 4-prong boosted large-radius jet is presented. 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 are reconstructed as large-radius jets and identified using a graph-neural-network-based jet substructure tagger. The standard model background contributions are estimated from the 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 and upper limits at the 95% confidence level are set on the signal strength as a function of the mediator mass and the coupling between the dark matter particles and the scalar mediator.
Links: CDS record (PDF) ; CADI line (restricted) ;

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: A representative Feynman diagram of the process under study producing displaced vertices and missing transverse energy, as outlined in Ref. [2].
png pdf	Figure 2: Distribution of $ s_{\mathrm{GNN}} $ in the SR before imposing any requirement on $ s_{\mathrm{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, is represented by the filled histogram. The lower panel shows the ratio of the data and the total background, and the hatched area represents the total uncertainty in the background.
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 error of that difference is reported.
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 error of that difference is reported.
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 error of that difference is reported.
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 error of that difference is reported.
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 error of that difference is reported.
png pdf	Figure 4: Upper limits at the 95% CL on the signal strength for different scenarios of the coupling $ g_{\chi_2\chi_1\mathrm{Y}_0} $ (left) and varying $ \mathrm{Y}_1 $ 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.
png pdf	Figure 4-a: Upper limits at the 95% CL on the signal strength for different scenarios of the coupling $ g_{\chi_2\chi_1\mathrm{Y}_0} $ (left) and varying $ \mathrm{Y}_1 $ 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.
png pdf	Figure 4-b: Upper limits at the 95% CL on the signal strength for different scenarios of the coupling $ g_{\chi_2\chi_1\mathrm{Y}_0} $ (left) and varying $ \mathrm{Y}_1 $ 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.

Tables
png pdf	Table 1: Combinations of particle masses and couplings probed in this search. The configurations in the upper block vary the coupling $ g_{\chi_2\chi_1\mathrm{Y}_0} $ for fixed masses of the new particles, whereas the configuration in the lower block vary the $ \mathrm{Y}_1 $ boson mass for otherwise constant parameters.
png pdf	Table 2: Tagger efficiency scale factors derived for representative signal parameter configurations.
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. The third column reports the effect of a given uncertainty on the normalization of the affected processes.

Summary

The first search for a displaced dark matter candidate in the 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} $. Candidate signal events were selected by requiring the presence of large-radius jets and identified using a graph-neural-network-based tagger that exploits jet substructure and secondary-vertex information. The dominant standard model backgrounds arise from quantum chromodymanics multijet production, $ \mathrm{Z}(\to\nu\nu)+\text{jets} $, and $ \mathrm{W}+\text{jets} $ processes, which were estimated from the data using dedicated control regions. The missing transverse momentum spectrum was analyzed to search for a potential signal above the expected background. Upper limits at the 95% confidence level were set on the signal strength as a function of the mediator mass and the coupling strength of the $ \chi_2\chi_1\mathrm{Y}_0 $ vertex. No significant excess over the SM expectation was observed.

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