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| CMS-PAS-SUS-24-008 | ||
| Search for exotic decays of the Higgs boson into a pair of light bosons with two b jets and two photons in the final state with full Run 2 dataset at 13 TeV | ||
| CMS Collaboration | ||
| 2026-05-31 | ||
| Abstract: A search is presented for the exotic decay of the Standard Model Higgs boson into a pair of light bosons (A) in the mass range 20--62 GeV, which decay into a pair of b quarks and a pair of photons, respectively. The analysis is based on the full Run 2 dataset recorded with the CMS detector at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of 137 $ \text{fb}^{-1} $. The search is performed in the VH (V=W/Z boson) production channel of the Higgs boson. No significant deviation from the standard model expectation is observed. Hence, model independent upper limits at 95 percent Confidence Level are set on the branching fraction $ \mathcal{B}(\text{H} \rightarrow \text{AA} \rightarrow \text{bb}\gamma\gamma) $ for the WH and ZH channels separately, in the leptonic decay modes of the vector bosons, as well as for their statistical combination. The observed (expected) upper limits on the $ \mathcal{B}(\text{H} \rightarrow \text{AA} \rightarrow \text{bb}\gamma\gamma) $ for the WH channel range from 0.04 (0.06) for $ m_{\text{A}} = $ 20 GeV to 0.07 (0.04) for $ m_{\text{A}} = $ 62 GeV. The upper limits presented for the combined channel are found to be dominated by the WH one. | ||
| Links: CDS record (PDF) ; CADI line (restricted) ; | ||
| Figures | |
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Figure 1:
Schematic diagram of the signal topology. Here `$ \ell $' can be either `$ e $', `$ \mu $' or `$ \tau $'. |
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Figure 2:
The $ \chi^2 $ distribution for the WH channel, combining the electron and muon channels across all three years of Run 2. The last bin includes the overflow. The simulated background processes include $ {\mathrm{t}\overline{\mathrm{t}}} $ (semileptonic and dileptonic decays), while contributions from other SM processes such as $ {\mathrm{t}\overline{\mathrm{t}}} +\gamma+\text{jets} $ and DY are grouped together and denoted as ``Other'', as shown in the legend. The data are represented by black points. Distributions for $ m_{A} = 20 \text{GeV} (\times20) $ and $ m_{A} = 60 \text{GeV} (\times20) $ signal hypotheses are overlaid. The gray band corresponds to the total uncertainty in the simulated samples, while the vertical bars on the data points indicate the statistical uncertainty of the data. |
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Figure 3:
The BDT score distribution for the WH channel, combining the electron and muon channels across all three years of Run 2. The simulated background processes include $ {\mathrm{t}\overline{\mathrm{t}}} $ (semileptonic and dileptonic decays), while contributions from other SM processes such as $ {\mathrm{t}\overline{\mathrm{t}}} +\gamma+\text{jets} $ and DY are grouped together and denoted as ``Other'', as shown in the legend. The data are represented by black points. Distributions for $ m_{A} = 20 \text{GeV} (\times50) $ and $ m_{A} = 55 \text{GeV} (\times50) $ signal hypotheses are overlaid. The gray band corresponds to the statistical uncertainty in the simulated samples, while the vertical bars on the data points indicate the statistical uncertainty of the data. The shaded region denotes the control region (CR), and the two vertical dashed lines indicate the BDT score boundaries that define the two analysis categories. |
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Figure 4:
The signal models for the $ m_{\text{A}} = $ 40 GeV mass hypothesis in the most significant (upper left) and least significant (upper right) categories of the WH channel, and for the ZH channel (lower). The effective standard deviation ($ \sigma_{\text{eff}} $), defined as half of the smallest interval that contains 68.3% of the invariant mass distribution, is provided for each model. |
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Figure 4-a:
The signal models for the $ m_{\text{A}} = $ 40 GeV mass hypothesis in the most significant (upper left) and least significant (upper right) categories of the WH channel, and for the ZH channel (lower). The effective standard deviation ($ \sigma_{\text{eff}} $), defined as half of the smallest interval that contains 68.3% of the invariant mass distribution, is provided for each model. |
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Figure 4-b:
The signal models for the $ m_{\text{A}} = $ 40 GeV mass hypothesis in the most significant (upper left) and least significant (upper right) categories of the WH channel, and for the ZH channel (lower). The effective standard deviation ($ \sigma_{\text{eff}} $), defined as half of the smallest interval that contains 68.3% of the invariant mass distribution, is provided for each model. |
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Figure 4-c:
The signal models for the $ m_{\text{A}} = $ 40 GeV mass hypothesis in the most significant (upper left) and least significant (upper right) categories of the WH channel, and for the ZH channel (lower). The effective standard deviation ($ \sigma_{\text{eff}} $), defined as half of the smallest interval that contains 68.3% of the invariant mass distribution, is provided for each model. |
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Figure 5:
The $ m_{\gamma\gamma} $ distributions for data (black points) and the fitted signal-plus-background models for $ m_{\text{A}} = $ 30 GeV in the most significant (left) and least significant (right) categories of the WH channel. The solid red line shows the total signal-plus-background contribution, whereas the dashed red line shows the background component only. The lower panel in each plot presents the residual data yield after background subtraction. The green and yellow bands present the one and two standard deviation uncertainties in the background component of the fit, respectively. |
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Figure 5-a:
The $ m_{\gamma\gamma} $ distributions for data (black points) and the fitted signal-plus-background models for $ m_{\text{A}} = $ 30 GeV in the most significant (left) and least significant (right) categories of the WH channel. The solid red line shows the total signal-plus-background contribution, whereas the dashed red line shows the background component only. The lower panel in each plot presents the residual data yield after background subtraction. The green and yellow bands present the one and two standard deviation uncertainties in the background component of the fit, respectively. |
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Figure 5-b:
The $ m_{\gamma\gamma} $ distributions for data (black points) and the fitted signal-plus-background models for $ m_{\text{A}} = $ 30 GeV in the most significant (left) and least significant (right) categories of the WH channel. The solid red line shows the total signal-plus-background contribution, whereas the dashed red line shows the background component only. The lower panel in each plot presents the residual data yield after background subtraction. The green and yellow bands present the one and two standard deviation uncertainties in the background component of the fit, respectively. |
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Figure 6:
The $ m_{\gamma\gamma} $ distribution for data (black points) and the fitted signal-plus-background model for $ m_{\text{A}} = $ 30 GeV in the ZH channel. The solid red line shows the total signal-plus-background contribution, whereas the dashed red line shows the background component only. The lower panel presents the residual data yield after background subtraction. The green and yellow bands present the one and two standard deviation uncertainties in the background component of the fit, respectively. |
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Figure 7:
The 95% confidence level (CL) upper limits on the product of the cross section and branching fraction, $ \sigma_{\text{WH}} \mathcal{B}(\text{H} \rightarrow \text{AA} \rightarrow \text{bb}\gamma\gamma) $, normalized to the SM prediction, for the WH channel. The yellow and blue bands represent the one and two standard deviation (68% and 95% CL) expected limit intervals, respectively. The limits are calculated assuming only the leptonic decay modes of $ \text{W} $ ($ \text{W} \rightarrow \ell\nu $; where $ \ell = $ e, $ \mu $ or $ \tau $) and $ \mathcal{B}(\text{H} \rightarrow \text{AA} \rightarrow \text{bb}\gamma\gamma) = 100% $. |
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Figure 8:
The 95% confidence level (CL) upper limits on the product of the cross section and branching fraction, $ \sigma_{\text{ZH}} \mathcal{B}(\text{H} \rightarrow \text{AA} \rightarrow \text{bb}\gamma\gamma) $, normalized to the SM prediction, for the ZH channel. The yellow and blue bands represent the one and two standard deviation (68% and 95% CL) expected limit intervals, respectively. The limits are calculated assuming only the leptonic decay modes of $ \text{Z} $ ($ \text{Z} \rightarrow \ell\ell $; where $ \ell = $ e, $ \mu $ or $ \tau $) and $ \mathcal{B}(\text{H} \rightarrow \text{AA} \rightarrow \text{bb}\gamma\gamma) = 100% $. |
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Figure 9:
The 95% confidence level (CL) upper limits on the product of the cross section and branching fraction, $ \sigma_{\text{VH}} \mathcal{B}(\text{H} \rightarrow \text{AA} \rightarrow \text{bb}\gamma\gamma) $, normalized to the SM prediction, for the combined WH and ZH channels. The yellow and blue bands represent the one and two standard deviation (68% and 95% CL) expected limit intervals, respectively. The limits are calculated assuming $ \mathcal{B}(\text{H} \rightarrow \text{AA} \rightarrow \text{bb}\gamma\gamma) = 100% $. |
| Tables | |
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Table 1:
Offline lepton $ p_{\mathrm{T}} $ thresholds for the WH and ZH channels. |
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Table 2:
BDT score boundaries and signal efficiencies in each category. |
| Summary |
| A search for the exotic decay of the standard model Higgs boson in the decay channel $ \text{H} \rightarrow \text{AA} \rightarrow \text{bb}\gamma\gamma $, using proton-proton collision data corresponding to an integrated luminosity of 137 $ \text{fb}^{-1} $, is presented. The search is performed in the WH and ZH production modes, where the W or Z boson decays leptonically, focusing on the $ m_{\text{A}} $ range from 20 to 62 GeV. In the absence of any significant excess of events over and above the SM prediction, model-independent upper limits on the branching fraction $ \mathcal{B}(\text{H} \rightarrow \text{AA} \rightarrow \text{bb}\gamma\gamma) $ are presented at the 95% confidence level. The observed (expected) upper limits on the branching fraction for the WH channel range from 0.04 (0.06) for $ m_{\text{A}} = $ 20 GeV to 0.07 (0.04) for $ m_{\text{A}} = $ 62 GeV. The combined upper limits are dominated by the WH channel. These are the first exclusion limits on a light boson arising from the SM Higgs boson decay in the $ \text{bb}\gamma\gamma $ final state at the LHC. |
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