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| CMS-PAS-SUS-23-005 | ||
| Search for a light pseudoscalar Higgs boson in final states with boosted $ \mu\mu $ and $ \tau\tau $ pairs in proton-proton collisions at $ \sqrt{s}= $ 13 TeV | ||
| CMS Collaboration | ||
| 2026-03-18 | ||
| Abstract: A search for a light pseudoscalar Higgs boson ($ \mathrm{a} $) is performed using LHC data collected at $ \sqrt{s}= $ 13 TeV by the CMS experiment from 2016 to 2018, targeting the process $ \mathrm{H} \to \mathrm{a}\mathrm{a} \to \mu\mu\tau\tau $, where the scalar H can be either the 125 GeV state or a heavier one. Due to the large mass difference between H and $ \mathrm{a} $, the two tau leptons are highly boosted and collimated, often failing standard CMS tau lepton reconstruction. To address this, dedicated di-tau reconstruction techniques, including a deep neural network, are developed to increase efficiency for cases where at least one tau decays to hadrons. No significant excess over standard model (SM) backgrounds is observed, and upper limits at the 95% confidence level are set on this process. Model-independent upper limits on the branching ratio for $ m_{\mathrm{H}}= $ 125 GeV range from 5 $ \times10^{-5} $ to 3 $ \times10^{-4} $ for pseudoscalar masses between 3.6 and 21 GeV. For the first time using LHC data, upper limits are obtained in final states with tau leptons for hypothetical scalar boson masses up to 1 TeV, with $ m_{\mathrm{H}}= $ 1 TeV limits ranging from 4 $ \times10^{-4} $ to 1.5 $ \times10^{-3} $ for pseudoscalar masses between 10 and 50 GeV. In addition, limits for SM extensions involving two-Higgs-doublet plus singlet models are set for $ m_{\mathrm{H}}= $ 125 GeV and extend previous LHC results. | ||
| Links: CDS record (PDF) ; CADI line (restricted) ; | ||
| Figures | |
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Figure 1:
Diagram of a Higgs boson produced by gluon-gluon fusion, decaying into two pseudoscalar bosons, with subsequent decays into two muons and two tau leptons. |
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Figure 2:
Confusion matrix for the DEEPDITAU classifier. |
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Figure 3:
Receiver operating characteristic (ROC) curve for the DEEPDITAU classifier. The true positive rate is the rate of correct classification of $ \tau_\mathrm{h}\tau_\mathrm{h} $ jets, and the false positive rate is the rate of classifying light-flavor jets and b jets as $ \tau_\mathrm{h}\tau_\mathrm{h} $ jets. |
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Figure 4:
The $ \tau\tau $ reconstruction efficiency of the standard $ \tau $ HPS (dashed lines) and a modified $ \tau_{\mu}\tau_\mathrm{h} $ (left) or $ \tau_{\mathrm{e}}\tau_\mathrm{h} $ (right) HPS (solid lines) reconstruction as a function of $ m_{\mathrm{a}} $ for $ m_{\mathrm{H}} = $ 125, 250, 500, 750, and 1000 GeV. Due to the requirement of $ \Delta R(\tau_{\ell}, \tau_\mathrm{h}) < $ 0.8, the efficiency for $ m_{\mathrm{H}} = $ 125 GeV drops above $ m_{\mathrm{a}} = $ 12 GeV ($ \tau_{\mu}\tau_\mathrm{h} $) and $ m_{\mathrm{a}} = $ 14 GeV ($ \tau_{\mathrm{e}}\tau_\mathrm{h} $), the region with increasingly more resolved $ \tau\tau $ topologies. In the right plot, the dip in the the standard HPS efficiency for the low $ m_{\mathrm{a}} $ region is due to two competing effects: the requirement of $ p_{\mathrm{T}}^{\mathrm{e}} > $ 10 GeV, which loses efficiency with increasing $ m_{\mathrm{a}} $, and the requirement of passing an anti-electron discriminant, which increases in efficiency as $ m_{\mathrm{a}} $ increases. Our analysis deploys the modified HPS reconstruction which shows a significantly higher efficiency than the standard $ \tau $ HPS scenario. |
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Figure 4-a:
The $ \tau\tau $ reconstruction efficiency of the standard $ \tau $ HPS (dashed lines) and a modified $ \tau_{\mu}\tau_\mathrm{h} $ (left) or $ \tau_{\mathrm{e}}\tau_\mathrm{h} $ (right) HPS (solid lines) reconstruction as a function of $ m_{\mathrm{a}} $ for $ m_{\mathrm{H}} = $ 125, 250, 500, 750, and 1000 GeV. Due to the requirement of $ \Delta R(\tau_{\ell}, \tau_\mathrm{h}) < $ 0.8, the efficiency for $ m_{\mathrm{H}} = $ 125 GeV drops above $ m_{\mathrm{a}} = $ 12 GeV ($ \tau_{\mu}\tau_\mathrm{h} $) and $ m_{\mathrm{a}} = $ 14 GeV ($ \tau_{\mathrm{e}}\tau_\mathrm{h} $), the region with increasingly more resolved $ \tau\tau $ topologies. In the right plot, the dip in the the standard HPS efficiency for the low $ m_{\mathrm{a}} $ region is due to two competing effects: the requirement of $ p_{\mathrm{T}}^{\mathrm{e}} > $ 10 GeV, which loses efficiency with increasing $ m_{\mathrm{a}} $, and the requirement of passing an anti-electron discriminant, which increases in efficiency as $ m_{\mathrm{a}} $ increases. Our analysis deploys the modified HPS reconstruction which shows a significantly higher efficiency than the standard $ \tau $ HPS scenario. |
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Figure 4-b:
The $ \tau\tau $ reconstruction efficiency of the standard $ \tau $ HPS (dashed lines) and a modified $ \tau_{\mu}\tau_\mathrm{h} $ (left) or $ \tau_{\mathrm{e}}\tau_\mathrm{h} $ (right) HPS (solid lines) reconstruction as a function of $ m_{\mathrm{a}} $ for $ m_{\mathrm{H}} = $ 125, 250, 500, 750, and 1000 GeV. Due to the requirement of $ \Delta R(\tau_{\ell}, \tau_\mathrm{h}) < $ 0.8, the efficiency for $ m_{\mathrm{H}} = $ 125 GeV drops above $ m_{\mathrm{a}} = $ 12 GeV ($ \tau_{\mu}\tau_\mathrm{h} $) and $ m_{\mathrm{a}} = $ 14 GeV ($ \tau_{\mathrm{e}}\tau_\mathrm{h} $), the region with increasingly more resolved $ \tau\tau $ topologies. In the right plot, the dip in the the standard HPS efficiency for the low $ m_{\mathrm{a}} $ region is due to two competing effects: the requirement of $ p_{\mathrm{T}}^{\mathrm{e}} > $ 10 GeV, which loses efficiency with increasing $ m_{\mathrm{a}} $, and the requirement of passing an anti-electron discriminant, which increases in efficiency as $ m_{\mathrm{a}} $ increases. Our analysis deploys the modified HPS reconstruction which shows a significantly higher efficiency than the standard $ \tau $ HPS scenario. |
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Figure 5:
Schematic of the analysis strategy. In the Z mass range, the tight-to-loose ratio is derived from the $ \mathrm{Z}_{\mu\mu}+ $jet control region and sideband (yellow). In the analysis mass range, events with two isolated muons and no loosely selected $ \tau\tau $ candidates enter the control region (yellow). Events that additionally contain a loosely selected $ \tau\tau $ candidate are further categorized into the signal region or sideband, as described in the text. The sideband data, weighted by the tight-to-loose ratio, are used to estimate the background in the signal region. Additionally, by inverting the isolation requirement on the muon that did not trigger the event, two analogous regions are formed for validating the tight-to-loose method (gray). |
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Figure 6:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_{\mu}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 125 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = 5 \times 10^{-4} $. |
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Figure 6-a:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_{\mu}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 125 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = 5 \times 10^{-4} $. |
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Figure 6-b:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_{\mu}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 125 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = 5 \times 10^{-4} $. |
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Figure 6-c:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_{\mu}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 125 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = 5 \times 10^{-4} $. |
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Figure 6-d:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_{\mu}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 125 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = 5 \times 10^{-4} $. |
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Figure 6-e:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_{\mu}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 125 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = 5 \times 10^{-4} $. |
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Figure 6-f:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_{\mu}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 125 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = 5 \times 10^{-4} $. |
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Figure 7:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 125 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
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Figure 7-a:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 125 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
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Figure 7-b:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 125 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
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Figure 7-c:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 125 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
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Figure 7-d:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 125 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
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Figure 7-e:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 125 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
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Figure 7-f:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 125 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
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Figure 8:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 250 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
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Figure 8-a:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 250 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
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Figure 8-b:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 250 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
png pdf |
Figure 8-c:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 250 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
png pdf |
Figure 8-d:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 250 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
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Figure 8-e:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 250 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
png pdf |
Figure 8-f:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 250 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
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Figure 9:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 500 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
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Figure 9-a:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 500 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
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Figure 9-b:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 500 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
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Figure 9-c:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 500 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
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Figure 9-d:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 500 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
png pdf |
Figure 9-e:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 500 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
png pdf |
Figure 9-f:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 500 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
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Figure 10:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 750 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
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Figure 10-a:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 750 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
png pdf |
Figure 10-b:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 750 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
png pdf |
Figure 10-c:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 750 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
png pdf |
Figure 10-d:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 750 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
png pdf |
Figure 10-e:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 750 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
png pdf |
Figure 10-f:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for $ m_{\mathrm{H}} = 750 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5, 11, and 20 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
png pdf |
Figure 11:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for the lower two $ m_{\mu\mu} $ mass ranges for $ m_{\mathrm{H}} = 1000 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5 and 11 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
png pdf |
Figure 11-a:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for the lower two $ m_{\mu\mu} $ mass ranges for $ m_{\mathrm{H}} = 1000 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5 and 11 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
png pdf |
Figure 11-b:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for the lower two $ m_{\mu\mu} $ mass ranges for $ m_{\mathrm{H}} = 1000 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5 and 11 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
png pdf |
Figure 11-c:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for the lower two $ m_{\mu\mu} $ mass ranges for $ m_{\mathrm{H}} = 1000 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5 and 11 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
png pdf |
Figure 11-d:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for the lower two $ m_{\mu\mu} $ mass ranges for $ m_{\mathrm{H}} = 1000 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 5 and 11 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
png pdf |
Figure 12:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for the higher two $ m_{\mu\mu} $ mass ranges for $ m_{\mathrm{H}} = 1000 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 20 and 50 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
png pdf |
Figure 12-a:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for the higher two $ m_{\mu\mu} $ mass ranges for $ m_{\mathrm{H}} = 1000 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 20 and 50 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
png pdf |
Figure 12-b:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for the higher two $ m_{\mu\mu} $ mass ranges for $ m_{\mathrm{H}} = 1000 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 20 and 50 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
png pdf |
Figure 12-c:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for the higher two $ m_{\mu\mu} $ mass ranges for $ m_{\mathrm{H}} = 1000 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 20 and 50 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
png pdf |
Figure 12-d:
Projections of the post-fit two-dimensional background PDFs (blue) and observed data onto the $ m_{\mu\mu} $ (left) and four-body visible mass (right) axes for the $ \tau_\mathrm{h}\tau_\mathrm{h} $ channel for the higher two $ m_{\mu\mu} $ mass ranges for $ m_{\mathrm{H}} = 1000 \text{GeV} $ using 2018 data. The rows correspond to pseudoscalar masses $ m_{\mathrm{a}} = $ 20 and 50 GeV (from top to bottom). Sample signal distributions (red) are overlaid assuming $ \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau) = $ 5 $ \times 10^{-4} $. |
png pdf |
Figure 13:
Expected and observed limits on $ \sigma_{\mathrm{H}} \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau)/\sigma_{SM} $ for the full Run 2 dataset of the $ \tau_{\mu}\tau_{\mathrm{e}} $, $ \tau_{\mu}\tau_\mathrm{h} $, $ \tau_{\mathrm{e}}\tau_\mathrm{h} $, and $ \tau_\mathrm{h}\tau_\mathrm{h} $ final states combined, for $ m_{\mathrm{H}} = $ 125, 250, 500, 750, and 1000 GeV. |
png pdf |
Figure 13-a:
Expected and observed limits on $ \sigma_{\mathrm{H}} \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau)/\sigma_{SM} $ for the full Run 2 dataset of the $ \tau_{\mu}\tau_{\mathrm{e}} $, $ \tau_{\mu}\tau_\mathrm{h} $, $ \tau_{\mathrm{e}}\tau_\mathrm{h} $, and $ \tau_\mathrm{h}\tau_\mathrm{h} $ final states combined, for $ m_{\mathrm{H}} = $ 125, 250, 500, 750, and 1000 GeV. |
png pdf |
Figure 13-b:
Expected and observed limits on $ \sigma_{\mathrm{H}} \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau)/\sigma_{SM} $ for the full Run 2 dataset of the $ \tau_{\mu}\tau_{\mathrm{e}} $, $ \tau_{\mu}\tau_\mathrm{h} $, $ \tau_{\mathrm{e}}\tau_\mathrm{h} $, and $ \tau_\mathrm{h}\tau_\mathrm{h} $ final states combined, for $ m_{\mathrm{H}} = $ 125, 250, 500, 750, and 1000 GeV. |
png pdf |
Figure 13-c:
Expected and observed limits on $ \sigma_{\mathrm{H}} \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau)/\sigma_{SM} $ for the full Run 2 dataset of the $ \tau_{\mu}\tau_{\mathrm{e}} $, $ \tau_{\mu}\tau_\mathrm{h} $, $ \tau_{\mathrm{e}}\tau_\mathrm{h} $, and $ \tau_\mathrm{h}\tau_\mathrm{h} $ final states combined, for $ m_{\mathrm{H}} = $ 125, 250, 500, 750, and 1000 GeV. |
png pdf |
Figure 13-d:
Expected and observed limits on $ \sigma_{\mathrm{H}} \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau)/\sigma_{SM} $ for the full Run 2 dataset of the $ \tau_{\mu}\tau_{\mathrm{e}} $, $ \tau_{\mu}\tau_\mathrm{h} $, $ \tau_{\mathrm{e}}\tau_\mathrm{h} $, and $ \tau_\mathrm{h}\tau_\mathrm{h} $ final states combined, for $ m_{\mathrm{H}} = $ 125, 250, 500, 750, and 1000 GeV. |
png pdf |
Figure 13-e:
Expected and observed limits on $ \sigma_{\mathrm{H}} \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau)/\sigma_{SM} $ for the full Run 2 dataset of the $ \tau_{\mu}\tau_{\mathrm{e}} $, $ \tau_{\mu}\tau_\mathrm{h} $, $ \tau_{\mathrm{e}}\tau_\mathrm{h} $, and $ \tau_\mathrm{h}\tau_\mathrm{h} $ final states combined, for $ m_{\mathrm{H}} = $ 125, 250, 500, 750, and 1000 GeV. |
png pdf |
Figure 14:
Expected and observed limits on $ \sigma_{\mathrm{H}} \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau)/\sigma_{SM} $ for the full Run 2 dataset, with the combined final states of the Higgs boson at different mass points when the pseudoscalar mass is (right) 10 GeV and (left) 15 GeV. |
png pdf |
Figure 14-a:
Expected and observed limits on $ \sigma_{\mathrm{H}} \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau)/\sigma_{SM} $ for the full Run 2 dataset, with the combined final states of the Higgs boson at different mass points when the pseudoscalar mass is (right) 10 GeV and (left) 15 GeV. |
png pdf |
Figure 14-b:
Expected and observed limits on $ \sigma_{\mathrm{H}} \mathcal{B}(\mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau)/\sigma_{SM} $ for the full Run 2 dataset, with the combined final states of the Higgs boson at different mass points when the pseudoscalar mass is (right) 10 GeV and (left) 15 GeV. |
png pdf |
Figure 15:
Observed and expected limits in 2HDM+S models of various types. The contours at a branching fraction of 0.16 are motivated by a CMS meta-analysis that sets limits on decays that would not be detected by the standard channels, such as those from boosted topologies considered in this analysis [18]. |
png pdf |
Figure 15-a:
Observed and expected limits in 2HDM+S models of various types. The contours at a branching fraction of 0.16 are motivated by a CMS meta-analysis that sets limits on decays that would not be detected by the standard channels, such as those from boosted topologies considered in this analysis [18]. |
png pdf |
Figure 15-b:
Observed and expected limits in 2HDM+S models of various types. The contours at a branching fraction of 0.16 are motivated by a CMS meta-analysis that sets limits on decays that would not be detected by the standard channels, such as those from boosted topologies considered in this analysis [18]. |
png pdf |
Figure 15-c:
Observed and expected limits in 2HDM+S models of various types. The contours at a branching fraction of 0.16 are motivated by a CMS meta-analysis that sets limits on decays that would not be detected by the standard channels, such as those from boosted topologies considered in this analysis [18]. |
png pdf |
Figure 15-d:
Observed and expected limits in 2HDM+S models of various types. The contours at a branching fraction of 0.16 are motivated by a CMS meta-analysis that sets limits on decays that would not be detected by the standard channels, such as those from boosted topologies considered in this analysis [18]. |
| Tables | |
png pdf |
Table 1:
Values of the scalar mass $ m_{\mathrm{H}} $ and pseudoscalar mass $ m_{\mathrm{a}} $ considered in the search for $ \mathrm{H}\to\mathrm{a}\mathrm{a}\to\mu\mu\tau\tau $. The third column lists the generated pseudoscalar mass points; ranges are shown together with the step size in parentheses. As $ m_{\mathrm{H}} $ increases, the maximum value of $ m_{\mathrm{a}} $ to which the search is sensitive also increases. For $ m_{\mathrm{H}}=125 \text{GeV} $, the lightest neutral scalar corresponds to the SM Higgs boson. |
png pdf |
Table 2:
The measured scale factors and their uncertainties for $ \tau_\mathrm{h} $ candidates using the full dataset. Data from 2016 comprise two eras with different strip tracker running conditions [65]. |
png pdf |
Table 3:
Tau lepton selection criteria in the four different channels. In the columns labeled $ \Delta R_{\mu\tau_{\ell}} $ and $ \Delta R_{\mu\tau_\mathrm{h}} $, $ \mu $ refers to either of the two muons reconstructed as the $ \mathrm{a}\rightarrow\mu\mu $ candidate. In the column labeled $ \Delta R_{\mu\tau_{\ell}} $, $ \tau_{\ell} $ refers to either of the $ \tau_{\mu} $ or $ \tau_{\mathrm{e}} $ candidates. $ \mu_{2} $ refers to the non-triggering muon in the $ \mathrm{a}\rightarrow\mu\mu $ pair. |
png pdf |
Table 4:
Four-body mass ranges utilized for the two-dimensional fit. For the $ \tau_{\mathrm{e}}\tau_\mathrm{h} $ channel an additional requirement is imposed on $ m_{\mu\mu} $, shown in the last row. All entries are in GeV. |
png pdf |
Table 5:
The $ \mu\mu $ background model includes five meson resonances, modeled using a Voigt function over an exponential continuum. The four-body background model is described by an error function multiplied by the sum of two exponential distributions. Two types of fit region relationships are used: (a) shared, where the parameters are identical in the indicated regions, and (b) independent, where the parameters vary freely and are not constrained by any other region. |
| Summary |
| A search for Higgs boson (H) decays to a pair of light pseudoscalar bosons ($ \mathrm{a} $) is presented, both for a SM Higgs and for a SM-like scalar with masses in the range 250 $ \text{GeV} $ - 1 $ \text{TeV} $. The light pseudoscalars decay to $ \mu\mu $ and $ \tau\tau $, with substantial overlap for each pair because of the large Lorentz boosts. This nonstandard topology motivates the development of dedicated $ \tau_{\mu}\tau_\mathrm{h} $, $ \tau_{\mathrm{e}}\tau_\mathrm{h} $, and $ \tau_\mathrm{h}\tau_\mathrm{h} $ reconstruction and tagging methods to increase acceptance. For the first time a neural network is developed to enable the inclusion of high-rate but high-background $ \tau_\mathrm{h}\tau_\mathrm{h} $ decays. Data collected by the CMS Collaboration at $ \sqrt{s} = 13 \text{TeV} $, corresponding to an integrated luminosity of 138 fb$ ^{-1} $, are examined. As no significant excess over standard model (SM) processes is observed, this analysis obtains model-independent upper limits at the 95% confidence level on the branching fraction $ (\mathcal{B}) $ of an SM-like Higgs boson (H), decaying to a pair of pseudoscalar bosons ($ \mathrm{a} $) in the $ \mu\mu\tau\tau $ final state, $ \sigma_{\mathrm{H}}\mathcal{B}(\mathrm{H} \to \mathrm{a}\mathrm{a} \to \mu\mu\tau\tau) / \sigma_{\text{SM}} $, with a maximum exclusion of $ \approx 5 \times 10^{-5} $ for $ m_{\mathrm{H}} = 125 \text{GeV} $ and a maximum exclusion of $ \approx 4 \times 10^{-4} $ for $ m_{\mathrm{H}} = 1000 \text{GeV} $. Model-specific upper limits on $ \sigma_{\mathrm{H}}\mathcal{B}(\mathrm{H} \to \mathrm{a}\mathrm{a}) / \sigma_{\text{SM}} $ are extracted for $ m_{\mathrm{H}} = 125 \text{GeV} $ in Type-I, -II, -III, and -IV two Higgs doublet plus singlet models. These results significantly extend the upper limits obtained by earlier searches by the CMS and ATLAS Collaborations, such as those obtained by CMS with partial 13 TeV data [45], and are complementary to present searches, $ \mbox{e.g.} $, Ref. [77], at higher $ m_{\mathrm{a}} $ that lead to resolved $ \mu\mu $ and $ \tau\tau $ final states. |
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