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| CMS-PAS-EXO-24-016 | ||
| Search for long-lived particles decaying into muons in proton-proton collisions at $ \sqrt{s}= $ 13.6 TeV using the CMS scouting data sets | ||
| CMS Collaboration | ||
| 2025-07-13 | ||
| Abstract: A search for long-lived particles decaying into muons is performed using proton-proton collisions at a center-of-mass energy of $ \sqrt{s}= $ 13.6 TeV, collected by the CMS experiment at the LHC in 2022 and 2023, corresponding to an integrated luminosity of 62.4 fb$ ^{-1} $. The data sets used in this search were collected with a dedicated dimuon trigger stream with low transverse momentum thresholds, recorded at high rate by retaining a reduced amount of information, in order to explore otherwise inaccessible phase space at low multimuon mass and nonzero displacement from the primary interaction vertex. No significant excess of events beyond the standard model expectation is found. Upper limits on branching fractions at 95% confidence level are set on a wide range of mass and lifetime hypotheses in beyond the standard model frameworks where the Higgs boson decays into long-lived particles. | ||
| Links: CDS record (PDF) ; CADI line (restricted) ; | ||
| Figures | |
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Figure 1:
Diagrams illustrating an SM-like Higgs boson (H) decay to four leptons ($ \ell $) via two intermediate dark photons, $ \mathrm{Z}_{\mathrm{D}} $ [6]: (left) through the hypercharge portal; (right) through the Higgs portal, via a dark Higgs boson ($ \mathrm{H}_{\mathrm{D}} $). |
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Figure 1-a:
Diagrams illustrating an SM-like Higgs boson (H) decay to four leptons ($ \ell $) via two intermediate dark photons, $ \mathrm{Z}_{\mathrm{D}} $ [6]: (left) through the hypercharge portal; (right) through the Higgs portal, via a dark Higgs boson ($ \mathrm{H}_{\mathrm{D}} $). |
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Figure 1-b:
Diagrams illustrating an SM-like Higgs boson (H) decay to four leptons ($ \ell $) via two intermediate dark photons, $ \mathrm{Z}_{\mathrm{D}} $ [6]: (left) through the hypercharge portal; (right) through the Higgs portal, via a dark Higgs boson ($ \mathrm{H}_{\mathrm{D}} $). |
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Figure 2:
Diagrams illustrating two dark shower scenarios [7] where the dark meson ($ \eta $) is allowed to decay into three dark pions ($ \pi_3 $) that subsequently decay into dark photons ($ \mathrm{A}^\prime $). (Left) Scenario A assumes prompt $ \pi_{3} $ decays into a pair of long-lived dark photons, $ \mathrm{A}^\prime $, each decaying into fermions. (Right) Scenario B1 assumes long-lived $ \pi_{3} $ decays into a pair of promptly decaying dark photons ($ \mathrm{A}^\prime $). |
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Figure 2-a:
Diagrams illustrating two dark shower scenarios [7] where the dark meson ($ \eta $) is allowed to decay into three dark pions ($ \pi_3 $) that subsequently decay into dark photons ($ \mathrm{A}^\prime $). (Left) Scenario A assumes prompt $ \pi_{3} $ decays into a pair of long-lived dark photons, $ \mathrm{A}^\prime $, each decaying into fermions. (Right) Scenario B1 assumes long-lived $ \pi_{3} $ decays into a pair of promptly decaying dark photons ($ \mathrm{A}^\prime $). |
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Figure 2-b:
Diagrams illustrating two dark shower scenarios [7] where the dark meson ($ \eta $) is allowed to decay into three dark pions ($ \pi_3 $) that subsequently decay into dark photons ($ \mathrm{A}^\prime $). (Left) Scenario A assumes prompt $ \pi_{3} $ decays into a pair of long-lived dark photons, $ \mathrm{A}^\prime $, each decaying into fermions. (Right) Scenario B1 assumes long-lived $ \pi_{3} $ decays into a pair of promptly decaying dark photons ($ \mathrm{A}^\prime $). |
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Figure 3:
Overall signal efficiency for representative mass points of the HAHM, as a function of the proper lifetime of the dark photon, for $ m_{\mathrm{Z}_{\mathrm{D}}} = $ 2, 5, 12 and 20 GeV. The efficiency is defined as the fraction of events with at least one dark photon decaying to muons that is reconstructed as a dimuon candidate within the $ l_\mathrm{xy} $ interval edges of [0.0, 0.2, 1.0, 2.4, 3.1, 7.0, 11.0, 16.0, 70.0] cm. The average efficiency over the 2022 and 2023 data taking periods is shown. |
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Figure 3-a:
Overall signal efficiency for representative mass points of the HAHM, as a function of the proper lifetime of the dark photon, for $ m_{\mathrm{Z}_{\mathrm{D}}} = $ 2, 5, 12 and 20 GeV. The efficiency is defined as the fraction of events with at least one dark photon decaying to muons that is reconstructed as a dimuon candidate within the $ l_\mathrm{xy} $ interval edges of [0.0, 0.2, 1.0, 2.4, 3.1, 7.0, 11.0, 16.0, 70.0] cm. The average efficiency over the 2022 and 2023 data taking periods is shown. |
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Figure 3-b:
Overall signal efficiency for representative mass points of the HAHM, as a function of the proper lifetime of the dark photon, for $ m_{\mathrm{Z}_{\mathrm{D}}} = $ 2, 5, 12 and 20 GeV. The efficiency is defined as the fraction of events with at least one dark photon decaying to muons that is reconstructed as a dimuon candidate within the $ l_\mathrm{xy} $ interval edges of [0.0, 0.2, 1.0, 2.4, 3.1, 7.0, 11.0, 16.0, 70.0] cm. The average efficiency over the 2022 and 2023 data taking periods is shown. |
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Figure 3-c:
Overall signal efficiency for representative mass points of the HAHM, as a function of the proper lifetime of the dark photon, for $ m_{\mathrm{Z}_{\mathrm{D}}} = $ 2, 5, 12 and 20 GeV. The efficiency is defined as the fraction of events with at least one dark photon decaying to muons that is reconstructed as a dimuon candidate within the $ l_\mathrm{xy} $ interval edges of [0.0, 0.2, 1.0, 2.4, 3.1, 7.0, 11.0, 16.0, 70.0] cm. The average efficiency over the 2022 and 2023 data taking periods is shown. |
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Figure 3-d:
Overall signal efficiency for representative mass points of the HAHM, as a function of the proper lifetime of the dark photon, for $ m_{\mathrm{Z}_{\mathrm{D}}} = $ 2, 5, 12 and 20 GeV. The efficiency is defined as the fraction of events with at least one dark photon decaying to muons that is reconstructed as a dimuon candidate within the $ l_\mathrm{xy} $ interval edges of [0.0, 0.2, 1.0, 2.4, 3.1, 7.0, 11.0, 16.0, 70.0] cm. The average efficiency over the 2022 and 2023 data taking periods is shown. |
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Figure 4:
Four-muon invariant mass spectra of the events in 2022 and 2023 with a four-muon system selected in the multivertex (left) or overlapping vertex (right) categories, for data (black) and different, representative signal models (colored histograms). |
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Figure 4-a:
Four-muon invariant mass spectra of the events in 2022 and 2023 with a four-muon system selected in the multivertex (left) or overlapping vertex (right) categories, for data (black) and different, representative signal models (colored histograms). |
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Figure 4-b:
Four-muon invariant mass spectra of the events in 2022 and 2023 with a four-muon system selected in the multivertex (left) or overlapping vertex (right) categories, for data (black) and different, representative signal models (colored histograms). |
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Figure 5:
Dimuon invariant mass spectra of the events in 2022 and 2023 with only a single dimuon pair selected, with isolated muons and with $ p_{\mathrm{T}}^{\mu\mu} > $ 25 GeV. Distributions are shown for each $ l_\mathrm{xy} $ bin separately, for $ l_\mathrm{xy} < $ 11 cm. The vertical gray bands indicate mass ranges containing known SM resonances, which are masked for the purpose of this search. Distributions are shown as obtained in data (black) and for different, representative signal models (colored histograms). |
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Figure 5-a:
Dimuon invariant mass spectra of the events in 2022 and 2023 with only a single dimuon pair selected, with isolated muons and with $ p_{\mathrm{T}}^{\mu\mu} > $ 25 GeV. Distributions are shown for each $ l_\mathrm{xy} $ bin separately, for $ l_\mathrm{xy} < $ 11 cm. The vertical gray bands indicate mass ranges containing known SM resonances, which are masked for the purpose of this search. Distributions are shown as obtained in data (black) and for different, representative signal models (colored histograms). |
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Figure 5-b:
Dimuon invariant mass spectra of the events in 2022 and 2023 with only a single dimuon pair selected, with isolated muons and with $ p_{\mathrm{T}}^{\mu\mu} > $ 25 GeV. Distributions are shown for each $ l_\mathrm{xy} $ bin separately, for $ l_\mathrm{xy} < $ 11 cm. The vertical gray bands indicate mass ranges containing known SM resonances, which are masked for the purpose of this search. Distributions are shown as obtained in data (black) and for different, representative signal models (colored histograms). |
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Figure 5-c:
Dimuon invariant mass spectra of the events in 2022 and 2023 with only a single dimuon pair selected, with isolated muons and with $ p_{\mathrm{T}}^{\mu\mu} > $ 25 GeV. Distributions are shown for each $ l_\mathrm{xy} $ bin separately, for $ l_\mathrm{xy} < $ 11 cm. The vertical gray bands indicate mass ranges containing known SM resonances, which are masked for the purpose of this search. Distributions are shown as obtained in data (black) and for different, representative signal models (colored histograms). |
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Figure 5-d:
Dimuon invariant mass spectra of the events in 2022 and 2023 with only a single dimuon pair selected, with isolated muons and with $ p_{\mathrm{T}}^{\mu\mu} > $ 25 GeV. Distributions are shown for each $ l_\mathrm{xy} $ bin separately, for $ l_\mathrm{xy} < $ 11 cm. The vertical gray bands indicate mass ranges containing known SM resonances, which are masked for the purpose of this search. Distributions are shown as obtained in data (black) and for different, representative signal models (colored histograms). |
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Figure 5-e:
Dimuon invariant mass spectra of the events in 2022 and 2023 with only a single dimuon pair selected, with isolated muons and with $ p_{\mathrm{T}}^{\mu\mu} > $ 25 GeV. Distributions are shown for each $ l_\mathrm{xy} $ bin separately, for $ l_\mathrm{xy} < $ 11 cm. The vertical gray bands indicate mass ranges containing known SM resonances, which are masked for the purpose of this search. Distributions are shown as obtained in data (black) and for different, representative signal models (colored histograms). |
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Figure 5-f:
Dimuon invariant mass spectra of the events in 2022 and 2023 with only a single dimuon pair selected, with isolated muons and with $ p_{\mathrm{T}}^{\mu\mu} > $ 25 GeV. Distributions are shown for each $ l_\mathrm{xy} $ bin separately, for $ l_\mathrm{xy} < $ 11 cm. The vertical gray bands indicate mass ranges containing known SM resonances, which are masked for the purpose of this search. Distributions are shown as obtained in data (black) and for different, representative signal models (colored histograms). |
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Figure 6:
Dimuon invariant mass spectra of the events in 2022 and 2023 with only a single dimuon pair selected, with isolated muons and with $ p_{\mathrm{T}}^{\mu\mu} > $ 25 GeV. Distributions are shown for each $ l_\mathrm{xy} $ bin separately, for $ l_\mathrm{xy} > $ 11 cm (i.e.,, for the displacement range inaccessible to the previous results presented in Ref. [16]). The vertical gray bands indicate mass ranges containing known SM resonances, which are masked for the purpose of this search. Distributions are shown as obtained in data (black) and for different, representative signal models (colored histograms). |
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Figure 6-a:
Dimuon invariant mass spectra of the events in 2022 and 2023 with only a single dimuon pair selected, with isolated muons and with $ p_{\mathrm{T}}^{\mu\mu} > $ 25 GeV. Distributions are shown for each $ l_\mathrm{xy} $ bin separately, for $ l_\mathrm{xy} > $ 11 cm (i.e.,, for the displacement range inaccessible to the previous results presented in Ref. [16]). The vertical gray bands indicate mass ranges containing known SM resonances, which are masked for the purpose of this search. Distributions are shown as obtained in data (black) and for different, representative signal models (colored histograms). |
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Figure 6-b:
Dimuon invariant mass spectra of the events in 2022 and 2023 with only a single dimuon pair selected, with isolated muons and with $ p_{\mathrm{T}}^{\mu\mu} > $ 25 GeV. Distributions are shown for each $ l_\mathrm{xy} $ bin separately, for $ l_\mathrm{xy} > $ 11 cm (i.e.,, for the displacement range inaccessible to the previous results presented in Ref. [16]). The vertical gray bands indicate mass ranges containing known SM resonances, which are masked for the purpose of this search. Distributions are shown as obtained in data (black) and for different, representative signal models (colored histograms). |
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Figure 7:
Dimuon invariant mass spectra of the events in 2022 and 2023 with only a single dimuon pair selected, with isolated muons and with $ p_{\mathrm{T}}^{\mu\mu} < $ 25 GeV. Distributions are shown for each $ l_\mathrm{xy} $ bin separately, for $ l_\mathrm{xy} > $ 11 cm. The vertical gray bands indicate mass ranges containing known SM resonances, which are masked for the purpose of this search. Distributions are shown as obtained in data (black) and for different, representative signal models (colored histograms). |
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Figure 7-a:
Dimuon invariant mass spectra of the events in 2022 and 2023 with only a single dimuon pair selected, with isolated muons and with $ p_{\mathrm{T}}^{\mu\mu} < $ 25 GeV. Distributions are shown for each $ l_\mathrm{xy} $ bin separately, for $ l_\mathrm{xy} > $ 11 cm. The vertical gray bands indicate mass ranges containing known SM resonances, which are masked for the purpose of this search. Distributions are shown as obtained in data (black) and for different, representative signal models (colored histograms). |
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Figure 7-b:
Dimuon invariant mass spectra of the events in 2022 and 2023 with only a single dimuon pair selected, with isolated muons and with $ p_{\mathrm{T}}^{\mu\mu} < $ 25 GeV. Distributions are shown for each $ l_\mathrm{xy} $ bin separately, for $ l_\mathrm{xy} > $ 11 cm. The vertical gray bands indicate mass ranges containing known SM resonances, which are masked for the purpose of this search. Distributions are shown as obtained in data (black) and for different, representative signal models (colored histograms). |
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Figure 7-c:
Dimuon invariant mass spectra of the events in 2022 and 2023 with only a single dimuon pair selected, with isolated muons and with $ p_{\mathrm{T}}^{\mu\mu} < $ 25 GeV. Distributions are shown for each $ l_\mathrm{xy} $ bin separately, for $ l_\mathrm{xy} > $ 11 cm. The vertical gray bands indicate mass ranges containing known SM resonances, which are masked for the purpose of this search. Distributions are shown as obtained in data (black) and for different, representative signal models (colored histograms). |
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Figure 7-d:
Dimuon invariant mass spectra of the events in 2022 and 2023 with only a single dimuon pair selected, with isolated muons and with $ p_{\mathrm{T}}^{\mu\mu} < $ 25 GeV. Distributions are shown for each $ l_\mathrm{xy} $ bin separately, for $ l_\mathrm{xy} > $ 11 cm. The vertical gray bands indicate mass ranges containing known SM resonances, which are masked for the purpose of this search. Distributions are shown as obtained in data (black) and for different, representative signal models (colored histograms). |
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Figure 7-e:
Dimuon invariant mass spectra of the events in 2022 and 2023 with only a single dimuon pair selected, with isolated muons and with $ p_{\mathrm{T}}^{\mu\mu} < $ 25 GeV. Distributions are shown for each $ l_\mathrm{xy} $ bin separately, for $ l_\mathrm{xy} > $ 11 cm. The vertical gray bands indicate mass ranges containing known SM resonances, which are masked for the purpose of this search. Distributions are shown as obtained in data (black) and for different, representative signal models (colored histograms). |
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Figure 7-f:
Dimuon invariant mass spectra of the events in 2022 and 2023 with only a single dimuon pair selected, with isolated muons and with $ p_{\mathrm{T}}^{\mu\mu} < $ 25 GeV. Distributions are shown for each $ l_\mathrm{xy} $ bin separately, for $ l_\mathrm{xy} > $ 11 cm. The vertical gray bands indicate mass ranges containing known SM resonances, which are masked for the purpose of this search. Distributions are shown as obtained in data (black) and for different, representative signal models (colored histograms). |
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Figure 8:
Dimuon invariant mass spectra of the events in 2022 and 2023 with only a single dimuon pair selected, with isolated muons and with $ p_{\mathrm{T}}^{\mu\mu} < $ 25 GeV. Distributions are shown for each $ l_\mathrm{xy} $ bin separately, for $ l_\mathrm{xy} > $ 11 cm (i.e.,, for the displacement range inaccessible to the previous results presented in Ref. [16]). The vertical gray bands indicate mass ranges containing known SM resonances, which are masked for the purpose of this search. Distributions are shown as obtained in data (black) and for different, representative signal models (colored histograms). |
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Figure 8-a:
Dimuon invariant mass spectra of the events in 2022 and 2023 with only a single dimuon pair selected, with isolated muons and with $ p_{\mathrm{T}}^{\mu\mu} < $ 25 GeV. Distributions are shown for each $ l_\mathrm{xy} $ bin separately, for $ l_\mathrm{xy} > $ 11 cm (i.e.,, for the displacement range inaccessible to the previous results presented in Ref. [16]). The vertical gray bands indicate mass ranges containing known SM resonances, which are masked for the purpose of this search. Distributions are shown as obtained in data (black) and for different, representative signal models (colored histograms). |
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Figure 8-b:
Dimuon invariant mass spectra of the events in 2022 and 2023 with only a single dimuon pair selected, with isolated muons and with $ p_{\mathrm{T}}^{\mu\mu} < $ 25 GeV. Distributions are shown for each $ l_\mathrm{xy} $ bin separately, for $ l_\mathrm{xy} > $ 11 cm (i.e.,, for the displacement range inaccessible to the previous results presented in Ref. [16]). The vertical gray bands indicate mass ranges containing known SM resonances, which are masked for the purpose of this search. Distributions are shown as obtained in data (black) and for different, representative signal models (colored histograms). |
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Figure 9:
(Left) The dimuon invariant mass distribution obtained using data collected in 2022 is shown in a mass window centered around 7 GeV, in one of the dimuon search bins (0.0 $ \leq l_\mathrm{xy} < $ 0.2 cm, $ p_{\mathrm{T}}^{\mu\mu} > $ 25 GeV, with two isolated muons) with the result of the background-only fit to the data where the three functional forms are visually indistinguishable. (Right) The fit to the dimuon invariant mass distribution expected for a representative $ \mathrm{H}\to\mathrm{Z}_{\mathrm{D}}\mathrm{Z}_{\mathrm{D}} $ signal model with $ m_{\mathrm{Z}_{\mathrm{D}}}= $ 7 GeV and $ c\tau_{0}^{\mathrm{Z}_{\mathrm{D}}}=$ 10 mm is also shown. |
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Figure 9-a:
(Left) The dimuon invariant mass distribution obtained using data collected in 2022 is shown in a mass window centered around 7 GeV, in one of the dimuon search bins (0.0 $ \leq l_\mathrm{xy} < $ 0.2 cm, $ p_{\mathrm{T}}^{\mu\mu} > $ 25 GeV, with two isolated muons) with the result of the background-only fit to the data where the three functional forms are visually indistinguishable. (Right) The fit to the dimuon invariant mass distribution expected for a representative $ \mathrm{H}\to\mathrm{Z}_{\mathrm{D}}\mathrm{Z}_{\mathrm{D}} $ signal model with $ m_{\mathrm{Z}_{\mathrm{D}}}= $ 7 GeV and $ c\tau_{0}^{\mathrm{Z}_{\mathrm{D}}}=$ 10 mm is also shown. |
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Figure 9-b:
(Left) The dimuon invariant mass distribution obtained using data collected in 2022 is shown in a mass window centered around 7 GeV, in one of the dimuon search bins (0.0 $ \leq l_\mathrm{xy} < $ 0.2 cm, $ p_{\mathrm{T}}^{\mu\mu} > $ 25 GeV, with two isolated muons) with the result of the background-only fit to the data where the three functional forms are visually indistinguishable. (Right) The fit to the dimuon invariant mass distribution expected for a representative $ \mathrm{H}\to\mathrm{Z}_{\mathrm{D}}\mathrm{Z}_{\mathrm{D}} $ signal model with $ m_{\mathrm{Z}_{\mathrm{D}}}= $ 7 GeV and $ c\tau_{0}^{\mathrm{Z}_{\mathrm{D}}}=$ 10 mm is also shown. |
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Figure 10:
Upper limits at 95% CL on the branching fraction $ \mathcal{B}(\mathrm{H}\to\mathrm{Z}_{\mathrm{D}}\mathrm{Z}_{\mathrm{D}}) $, as functions of the signal mass ($ m_{\mathrm{Z}_{\mathrm{D}}} $) for $ c\tau_{0}^{\mathrm{Z}_{\mathrm{D}}}= $ 0.1 cm (upper left), 1 cm (upper right), 10 cm (lower left) and 100 cm (lower right). The solid black (dashed red) line represents the observed (median expected) exclusion. The inner blue (outer yellow) band indicates the region containing 68 (95)% of the distribution of limits expected under the background-only hypothesis. The dark blue (magenta) solid line represents the upper limits previously set in Ref. [16] (Ref. [18]). The vertical gray bands indicate mass ranges containing known SM resonances, which are masked for the purpose of this search. The limits are obtained using the combination of all event categories. |
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Figure 10-a:
Upper limits at 95% CL on the branching fraction $ \mathcal{B}(\mathrm{H}\to\mathrm{Z}_{\mathrm{D}}\mathrm{Z}_{\mathrm{D}}) $, as functions of the signal mass ($ m_{\mathrm{Z}_{\mathrm{D}}} $) for $ c\tau_{0}^{\mathrm{Z}_{\mathrm{D}}}= $ 0.1 cm (upper left), 1 cm (upper right), 10 cm (lower left) and 100 cm (lower right). The solid black (dashed red) line represents the observed (median expected) exclusion. The inner blue (outer yellow) band indicates the region containing 68 (95)% of the distribution of limits expected under the background-only hypothesis. The dark blue (magenta) solid line represents the upper limits previously set in Ref. [16] (Ref. [18]). The vertical gray bands indicate mass ranges containing known SM resonances, which are masked for the purpose of this search. The limits are obtained using the combination of all event categories. |
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Figure 10-b:
Upper limits at 95% CL on the branching fraction $ \mathcal{B}(\mathrm{H}\to\mathrm{Z}_{\mathrm{D}}\mathrm{Z}_{\mathrm{D}}) $, as functions of the signal mass ($ m_{\mathrm{Z}_{\mathrm{D}}} $) for $ c\tau_{0}^{\mathrm{Z}_{\mathrm{D}}}= $ 0.1 cm (upper left), 1 cm (upper right), 10 cm (lower left) and 100 cm (lower right). The solid black (dashed red) line represents the observed (median expected) exclusion. The inner blue (outer yellow) band indicates the region containing 68 (95)% of the distribution of limits expected under the background-only hypothesis. The dark blue (magenta) solid line represents the upper limits previously set in Ref. [16] (Ref. [18]). The vertical gray bands indicate mass ranges containing known SM resonances, which are masked for the purpose of this search. The limits are obtained using the combination of all event categories. |
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Figure 10-c:
Upper limits at 95% CL on the branching fraction $ \mathcal{B}(\mathrm{H}\to\mathrm{Z}_{\mathrm{D}}\mathrm{Z}_{\mathrm{D}}) $, as functions of the signal mass ($ m_{\mathrm{Z}_{\mathrm{D}}} $) for $ c\tau_{0}^{\mathrm{Z}_{\mathrm{D}}}= $ 0.1 cm (upper left), 1 cm (upper right), 10 cm (lower left) and 100 cm (lower right). The solid black (dashed red) line represents the observed (median expected) exclusion. The inner blue (outer yellow) band indicates the region containing 68 (95)% of the distribution of limits expected under the background-only hypothesis. The dark blue (magenta) solid line represents the upper limits previously set in Ref. [16] (Ref. [18]). The vertical gray bands indicate mass ranges containing known SM resonances, which are masked for the purpose of this search. The limits are obtained using the combination of all event categories. |
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Figure 10-d:
Upper limits at 95% CL on the branching fraction $ \mathcal{B}(\mathrm{H}\to\mathrm{Z}_{\mathrm{D}}\mathrm{Z}_{\mathrm{D}}) $, as functions of the signal mass ($ m_{\mathrm{Z}_{\mathrm{D}}} $) for $ c\tau_{0}^{\mathrm{Z}_{\mathrm{D}}}= $ 0.1 cm (upper left), 1 cm (upper right), 10 cm (lower left) and 100 cm (lower right). The solid black (dashed red) line represents the observed (median expected) exclusion. The inner blue (outer yellow) band indicates the region containing 68 (95)% of the distribution of limits expected under the background-only hypothesis. The dark blue (magenta) solid line represents the upper limits previously set in Ref. [16] (Ref. [18]). The vertical gray bands indicate mass ranges containing known SM resonances, which are masked for the purpose of this search. The limits are obtained using the combination of all event categories. |
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Figure 11:
Upper limits at 95% CL on the branching fraction $ \mathcal{B}(\mathrm{H}\to\mathrm{Z}_{\mathrm{D}}\mathrm{Z}_{\mathrm{D}}) $, as functions of the dark photon $ c\tau_{0}^{\mathrm{Z}_{\mathrm{D}}} $ for representative masses $ m_{\mathrm{Z}_{\mathrm{D}}} = $ 2, 5, 12, and 20 GeV. The solid black (dashed red) line represents the observed (median expected) exclusion. The inner blue (outer yellow) band indicates the region containing 68 (95)% of the distribution of limits expected under the background-only hypothesis. The dark blue (magenta) solid line represents the upper limits previously set in Ref. [16] (Ref. [18]). The limits are obtained using the combination of all event categories. |
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Figure 11-a:
Upper limits at 95% CL on the branching fraction $ \mathcal{B}(\mathrm{H}\to\mathrm{Z}_{\mathrm{D}}\mathrm{Z}_{\mathrm{D}}) $, as functions of the dark photon $ c\tau_{0}^{\mathrm{Z}_{\mathrm{D}}} $ for representative masses $ m_{\mathrm{Z}_{\mathrm{D}}} = $ 2, 5, 12, and 20 GeV. The solid black (dashed red) line represents the observed (median expected) exclusion. The inner blue (outer yellow) band indicates the region containing 68 (95)% of the distribution of limits expected under the background-only hypothesis. The dark blue (magenta) solid line represents the upper limits previously set in Ref. [16] (Ref. [18]). The limits are obtained using the combination of all event categories. |
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Figure 11-b:
Upper limits at 95% CL on the branching fraction $ \mathcal{B}(\mathrm{H}\to\mathrm{Z}_{\mathrm{D}}\mathrm{Z}_{\mathrm{D}}) $, as functions of the dark photon $ c\tau_{0}^{\mathrm{Z}_{\mathrm{D}}} $ for representative masses $ m_{\mathrm{Z}_{\mathrm{D}}} = $ 2, 5, 12, and 20 GeV. The solid black (dashed red) line represents the observed (median expected) exclusion. The inner blue (outer yellow) band indicates the region containing 68 (95)% of the distribution of limits expected under the background-only hypothesis. The dark blue (magenta) solid line represents the upper limits previously set in Ref. [16] (Ref. [18]). The limits are obtained using the combination of all event categories. |
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Figure 11-c:
Upper limits at 95% CL on the branching fraction $ \mathcal{B}(\mathrm{H}\to\mathrm{Z}_{\mathrm{D}}\mathrm{Z}_{\mathrm{D}}) $, as functions of the dark photon $ c\tau_{0}^{\mathrm{Z}_{\mathrm{D}}} $ for representative masses $ m_{\mathrm{Z}_{\mathrm{D}}} = $ 2, 5, 12, and 20 GeV. The solid black (dashed red) line represents the observed (median expected) exclusion. The inner blue (outer yellow) band indicates the region containing 68 (95)% of the distribution of limits expected under the background-only hypothesis. The dark blue (magenta) solid line represents the upper limits previously set in Ref. [16] (Ref. [18]). The limits are obtained using the combination of all event categories. |
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Figure 11-d:
Upper limits at 95% CL on the branching fraction $ \mathcal{B}(\mathrm{H}\to\mathrm{Z}_{\mathrm{D}}\mathrm{Z}_{\mathrm{D}}) $, as functions of the dark photon $ c\tau_{0}^{\mathrm{Z}_{\mathrm{D}}} $ for representative masses $ m_{\mathrm{Z}_{\mathrm{D}}} = $ 2, 5, 12, and 20 GeV. The solid black (dashed red) line represents the observed (median expected) exclusion. The inner blue (outer yellow) band indicates the region containing 68 (95)% of the distribution of limits expected under the background-only hypothesis. The dark blue (magenta) solid line represents the upper limits previously set in Ref. [16] (Ref. [18]). The limits are obtained using the combination of all event categories. |
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Figure 12:
Upper limits at 95% CL on the branching fraction $ \mathcal{B}(\mathrm{H}\to\Psi\Psi) $, for two representative mass points in the Scenario A of the considered dark shower benchmark model. Limits are shown for masses of $ m_{\pi_3} = $ 2 GeV and $ m_{\mathrm{A}^\prime} = $ 0.67 GeV (left) and $ m_{\pi_3} = $ 4 GeV and $ m_{\mathrm{A}^\prime} = $ 1.33 GeV (right), as a function of $ c\tau_{0}^{\mathrm{A}^\prime} $. For this model, it is assumed $ m_\eta = \tilde{\Lambda} = 4m_{\pi_2} $, $ \sin\theta = $ 0.1 and $ B(\pi_{3} \to \mathrm{A}^\prime\mathrm{A}^\prime)= $ 1. The solid black (dashed red) line represents the observed (median expected) exclusion. The inner blue (outer yellow) band indicates the region containing 68 (95)% of the distribution of limits expected under the background-only hypothesis. The dark blue solid line represents the upper limits previously set in Ref. [43]. The limits are obtained using the combination of all event categories. |
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Figure 12-a:
Upper limits at 95% CL on the branching fraction $ \mathcal{B}(\mathrm{H}\to\Psi\Psi) $, for two representative mass points in the Scenario A of the considered dark shower benchmark model. Limits are shown for masses of $ m_{\pi_3} = $ 2 GeV and $ m_{\mathrm{A}^\prime} = $ 0.67 GeV (left) and $ m_{\pi_3} = $ 4 GeV and $ m_{\mathrm{A}^\prime} = $ 1.33 GeV (right), as a function of $ c\tau_{0}^{\mathrm{A}^\prime} $. For this model, it is assumed $ m_\eta = \tilde{\Lambda} = 4m_{\pi_2} $, $ \sin\theta = $ 0.1 and $ B(\pi_{3} \to \mathrm{A}^\prime\mathrm{A}^\prime)= $ 1. The solid black (dashed red) line represents the observed (median expected) exclusion. The inner blue (outer yellow) band indicates the region containing 68 (95)% of the distribution of limits expected under the background-only hypothesis. The dark blue solid line represents the upper limits previously set in Ref. [43]. The limits are obtained using the combination of all event categories. |
png pdf |
Figure 12-b:
Upper limits at 95% CL on the branching fraction $ \mathcal{B}(\mathrm{H}\to\Psi\Psi) $, for two representative mass points in the Scenario A of the considered dark shower benchmark model. Limits are shown for masses of $ m_{\pi_3} = $ 2 GeV and $ m_{\mathrm{A}^\prime} = $ 0.67 GeV (left) and $ m_{\pi_3} = $ 4 GeV and $ m_{\mathrm{A}^\prime} = $ 1.33 GeV (right), as a function of $ c\tau_{0}^{\mathrm{A}^\prime} $. For this model, it is assumed $ m_\eta = \tilde{\Lambda} = 4m_{\pi_2} $, $ \sin\theta = $ 0.1 and $ B(\pi_{3} \to \mathrm{A}^\prime\mathrm{A}^\prime)= $ 1. The solid black (dashed red) line represents the observed (median expected) exclusion. The inner blue (outer yellow) band indicates the region containing 68 (95)% of the distribution of limits expected under the background-only hypothesis. The dark blue solid line represents the upper limits previously set in Ref. [43]. The limits are obtained using the combination of all event categories. |
png pdf |
Figure 13:
Upper limits at 95% CL on the branching fraction $ \mathcal{B}(\mathrm{H}\to\Psi\Psi) $, for two representative mass points in the Scenario B1 of the considered dark shower benchmark model. Limits are shown for masses of $ m_{\pi_3} = $ 2 GeV and $ m_{\mathrm{A}^\prime} = $ 0.67 GeV (left) and $ m_{\pi_3} = $ 4 GeV and $ m_{\mathrm{A}^\prime} = $ 1.33 GeV (right), as a function of $ c\tau_{0}^{\pi_3} $. For this model, it is assumed $ m_\eta = \tilde{\Lambda} = 4m_{\pi_2} $, $ \sin\theta = $ 0.1 and $ B(\pi_{3} \to \mathrm{A}^\prime\mathrm{A}^\prime)= $ 1. The solid black (dashed red) line represents the observed (median expected) exclusion. The inner blue (outer yellow) band indicates the region containing 68 (95)% of the distribution of limits expected under the background-only hypothesis. The dark blue solid line represents the upper limits previously set in Ref. [43]. The limits are obtained using the combination of all event categories. |
png pdf |
Figure 13-a:
Upper limits at 95% CL on the branching fraction $ \mathcal{B}(\mathrm{H}\to\Psi\Psi) $, for two representative mass points in the Scenario B1 of the considered dark shower benchmark model. Limits are shown for masses of $ m_{\pi_3} = $ 2 GeV and $ m_{\mathrm{A}^\prime} = $ 0.67 GeV (left) and $ m_{\pi_3} = $ 4 GeV and $ m_{\mathrm{A}^\prime} = $ 1.33 GeV (right), as a function of $ c\tau_{0}^{\pi_3} $. For this model, it is assumed $ m_\eta = \tilde{\Lambda} = 4m_{\pi_2} $, $ \sin\theta = $ 0.1 and $ B(\pi_{3} \to \mathrm{A}^\prime\mathrm{A}^\prime)= $ 1. The solid black (dashed red) line represents the observed (median expected) exclusion. The inner blue (outer yellow) band indicates the region containing 68 (95)% of the distribution of limits expected under the background-only hypothesis. The dark blue solid line represents the upper limits previously set in Ref. [43]. The limits are obtained using the combination of all event categories. |
png pdf |
Figure 13-b:
Upper limits at 95% CL on the branching fraction $ \mathcal{B}(\mathrm{H}\to\Psi\Psi) $, for two representative mass points in the Scenario B1 of the considered dark shower benchmark model. Limits are shown for masses of $ m_{\pi_3} = $ 2 GeV and $ m_{\mathrm{A}^\prime} = $ 0.67 GeV (left) and $ m_{\pi_3} = $ 4 GeV and $ m_{\mathrm{A}^\prime} = $ 1.33 GeV (right), as a function of $ c\tau_{0}^{\pi_3} $. For this model, it is assumed $ m_\eta = \tilde{\Lambda} = 4m_{\pi_2} $, $ \sin\theta = $ 0.1 and $ B(\pi_{3} \to \mathrm{A}^\prime\mathrm{A}^\prime)= $ 1. The solid black (dashed red) line represents the observed (median expected) exclusion. The inner blue (outer yellow) band indicates the region containing 68 (95)% of the distribution of limits expected under the background-only hypothesis. The dark blue solid line represents the upper limits previously set in Ref. [43]. The limits are obtained using the combination of all event categories. |
| Summary |
| A search for displaced multimuon resonances has been performed using proton-proton collisions at a center-of-mass energy of 13.6 TeV, collected by the CMS experiment at the LHC in 2022 and 2023, corresponding to an integrated luminosity of 62.4 fb$^{-1}$. The data sets used in this search are collected using a dedicated dimuon trigger stream with low transverse momentum thresholds, recorded at high rate by retaining a reduced amount of information, in order to explore otherwise inaccessible phase space at low dimuon mass and nonzero displacement from the primary interaction vertex. No significant excess beyond the standard model expectation is found, and the data are used to set constraints on a wide range of mass and lifetime hypotheses for models of physics beyond the standard model (BSM) where a Higgs boson decays to long-lived dark particles. Two sets of models are considered: the Hidden Abelian Higgs Model (HAHM), where the Higgs boson H decays to a pair of long-lived dark photons $ \mathrm{Z}_{\mathrm{D}} $, and dark shower models, where dark showers originate by H decays to dark quarks. The constraints obtained are the most stringent to date for a significant fraction of the probed parameter space. In the HAHM, the most stringent limits to date are obtained for $ c\tau_{0}^{\mathrm{Z}_{\mathrm{D}}}\gtrsim1\,\text{cm} $ and $ m_{\mathrm{Z}_{\mathrm{D}}}\lesssim $ 5 GeV. In the dark shower models, where the dark photon is assumed to have a mass smaller than 5 GeV, we set the most stringent constraints to date for lifetimes $ \lesssim $0.01 cm ($ \gtrsim $10 cm) when Scenario A (Scenario B1) is considered. |
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Compact Muon Solenoid LHC, CERN |
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