CMSPASHIG22012  
Search for the nonresonant and resonant production of a Higgs boson in association with an additional scalar boson in the $ \gamma\gamma\tau\tau $ final state  
CMS Collaboration  
26 March 2024  
Abstract: Protonproton interactions resulting in final states with two photons and two tau leptons are studied in a search for the production of two scalar bosons. The search considers both nonresonant production of a Higgs boson pair, HH, and resonant production via a new boson X which decays either to HH or to H and a new scalar Y. The analysis uses 138 fb$^{1}$ of data collected at a centerofmass energy of 13 TeV with the CMS detector at the LHC from 2016 to 2018. An observed (expected) upper limit at the 95% confidence level (CL) on the HH production cross section is found to be 930 (740) fb, corresponding to 33 (26) times the standard model prediction. The observed (expected) constraint on the Higgs boson selfcoupling is $ 13 (11) < \kappa_\lambda < $ 18 (16) at the 95% CL. Observed (expected) upper limits at the 95% CL for the $ \mathrm{X}\to\mathrm{HH} $ cross section are found to be within 140 to 2200 (200 to 1700) fb depending on $ m_\mathrm{X} $. In the $ \mathrm{X}\to\mathrm{YH} $ scenario, the most significant excess is found for $ m_\mathrm{X}= $ 525 GeV and $ m_\mathrm{Y}= $ 115 GeV in the $ \mathrm{Y}\to\gamma\gamma $ decay channel and has a local (global) significance of 3.4 (0.1) standard deviations. In the $ \mathrm{Y}\to\tau\tau $ decay channel, an excess at $ m_\mathrm{X}= $ 320 GeV and $ m_\mathrm{Y}= $ 60 GeV is found with a local (global) significance of 2.6 (2.2) standard deviations.  
Links: CDS record (PDF) ; CADI line (restricted) ; 
Figures & Tables  Summary  Additional Figures  References  CMS Publications 

Figures  
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Figure 1:
Leading order Feynman diagrams of the nonresonant HH production via ggF. The two diagrams in the upper row correspond to SM processes, involving the top Yukawa coupling $ y_\mathrm{t} $ and the trilinear Higgs boson selfcoupling $ \lambda_{\mathrm{H}\mathrm{H}\mathrm{H}} $. The diagrams in the lower row correspond to BSM processes involving contact interactions introduced in the effective field theory, namely $ c_2 $, $ c_{2\mathrm{g}} $ and $ c_{\mathrm{g}} $. 
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Figure 2:
Feynman diagram of the resonant production of a pair of SM Higgs bosons ($ \mathrm{X} \to \mathrm{H}\mathrm{H} $) or a SM Higgs boson and a new scalar particle ($ \mathrm{X} \to \mathrm{Y}\mathrm{H} $). 
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Figure 3:
Distribution of the BDT scores used for the nonresonant analysis event categorization from data (black points) and predictions from MC simulation (coloured histograms). The ``H'' process includes ggH, VBF, VH, and $ {\mathrm{t}\overline{\mathrm{t}}} $H. The background histograms are stacked, while the signal distribution is shown separately. The normalization of the signal distribution is set to 25 times the SM prediction and the background MC simulation is normalized to data. The ratio of the data to the sum of the background predictions is shown in the lower panel. Statistical MC uncertainties for the background are represented by the greyshaded bands. The grey dotted lines represent the boundaries that define the analysis categories. 
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Figure 4:
Transformed output of the pNN used in the $ \mathrm{X}^{(2)} \to \mathrm{H}\mathrm{H} $ search, evaluated at $ m_{\mathrm{X}}= $ 260 GeV (left) and $ m_{\mathrm{X}}= $ 800 GeV (right). The filled histograms represent the background simulation, and the data are shown by the black points. The ``H'' process includes ggH, VBF, VH, and $ {\mathrm{t}\overline{\mathrm{t}}} $H. The targeted signal distributions for which the pNN is evaluated are shown by the black unfilled histograms. The background MC simulation is normalized to data and the signal is normalized to an arbitrary cross section for representation purposes. The ratio of the data to the sum of the background predictions is shown in the lower panel. Statistical MC uncertainties for the background are represented by the greyshaded bands. 
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Figure 4a:
Transformed output of the pNN used in the $ \mathrm{X}^{(2)} \to \mathrm{H}\mathrm{H} $ search, evaluated at $ m_{\mathrm{X}}= $ 260 GeV (left) and $ m_{\mathrm{X}}= $ 800 GeV (right). The filled histograms represent the background simulation, and the data are shown by the black points. The ``H'' process includes ggH, VBF, VH, and $ {\mathrm{t}\overline{\mathrm{t}}} $H. The targeted signal distributions for which the pNN is evaluated are shown by the black unfilled histograms. The background MC simulation is normalized to data and the signal is normalized to an arbitrary cross section for representation purposes. The ratio of the data to the sum of the background predictions is shown in the lower panel. Statistical MC uncertainties for the background are represented by the greyshaded bands. 
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Figure 4b:
Transformed output of the pNN used in the $ \mathrm{X}^{(2)} \to \mathrm{H}\mathrm{H} $ search, evaluated at $ m_{\mathrm{X}}= $ 260 GeV (left) and $ m_{\mathrm{X}}= $ 800 GeV (right). The filled histograms represent the background simulation, and the data are shown by the black points. The ``H'' process includes ggH, VBF, VH, and $ {\mathrm{t}\overline{\mathrm{t}}} $H. The targeted signal distributions for which the pNN is evaluated are shown by the black unfilled histograms. The background MC simulation is normalized to data and the signal is normalized to an arbitrary cross section for representation purposes. The ratio of the data to the sum of the background predictions is shown in the lower panel. Statistical MC uncertainties for the background are represented by the greyshaded bands. 
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Figure 5:
Transformed output of the pNNs used in the $ \mathrm{X}^{(0)} \to \mathrm{H}\mathrm{H} $ (top left), $ \mathrm{X}^{(2)} \to \mathrm{H}\mathrm{H} $ (top right), $ \mathrm{X} \to \mathrm{Y}(\tau\tau)\mathrm{H}(\gamma\gamma) $ (middle), lowmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ (bottom left) and highmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ (bottom right) searches. The pNNs are evaluated at the mass points where the largest excess with respect to the backgroundonly hypothesis is observed. If the MC simulation at this mass point is not available, then the sample produced at a mass point closest to the excess is shown. The filled histograms represent the background simulation, and the data are shown by the black points. The ``H'' process includes ggH, VBF, VH, and $ {\mathrm{t}\overline{\mathrm{t}}} $H. The targeted signal distributions for which the pNN is evaluated are shown by the black unfilled histograms. The background MC simulation is normalized to data and the signal is normalized to an arbitrary cross section for representation purposes. The ratio of the data to the sum of the background predictions is shown in the lower panel. Statistical MC uncertainties for the background are represented by the greyshaded bands. 
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Figure 5a:
Transformed output of the pNNs used in the $ \mathrm{X}^{(0)} \to \mathrm{H}\mathrm{H} $ (top left), $ \mathrm{X}^{(2)} \to \mathrm{H}\mathrm{H} $ (top right), $ \mathrm{X} \to \mathrm{Y}(\tau\tau)\mathrm{H}(\gamma\gamma) $ (middle), lowmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ (bottom left) and highmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ (bottom right) searches. The pNNs are evaluated at the mass points where the largest excess with respect to the backgroundonly hypothesis is observed. If the MC simulation at this mass point is not available, then the sample produced at a mass point closest to the excess is shown. The filled histograms represent the background simulation, and the data are shown by the black points. The ``H'' process includes ggH, VBF, VH, and $ {\mathrm{t}\overline{\mathrm{t}}} $H. The targeted signal distributions for which the pNN is evaluated are shown by the black unfilled histograms. The background MC simulation is normalized to data and the signal is normalized to an arbitrary cross section for representation purposes. The ratio of the data to the sum of the background predictions is shown in the lower panel. Statistical MC uncertainties for the background are represented by the greyshaded bands. 
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Figure 5b:
Transformed output of the pNNs used in the $ \mathrm{X}^{(0)} \to \mathrm{H}\mathrm{H} $ (top left), $ \mathrm{X}^{(2)} \to \mathrm{H}\mathrm{H} $ (top right), $ \mathrm{X} \to \mathrm{Y}(\tau\tau)\mathrm{H}(\gamma\gamma) $ (middle), lowmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ (bottom left) and highmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ (bottom right) searches. The pNNs are evaluated at the mass points where the largest excess with respect to the backgroundonly hypothesis is observed. If the MC simulation at this mass point is not available, then the sample produced at a mass point closest to the excess is shown. The filled histograms represent the background simulation, and the data are shown by the black points. The ``H'' process includes ggH, VBF, VH, and $ {\mathrm{t}\overline{\mathrm{t}}} $H. The targeted signal distributions for which the pNN is evaluated are shown by the black unfilled histograms. The background MC simulation is normalized to data and the signal is normalized to an arbitrary cross section for representation purposes. The ratio of the data to the sum of the background predictions is shown in the lower panel. Statistical MC uncertainties for the background are represented by the greyshaded bands. 
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Figure 5c:
Transformed output of the pNNs used in the $ \mathrm{X}^{(0)} \to \mathrm{H}\mathrm{H} $ (top left), $ \mathrm{X}^{(2)} \to \mathrm{H}\mathrm{H} $ (top right), $ \mathrm{X} \to \mathrm{Y}(\tau\tau)\mathrm{H}(\gamma\gamma) $ (middle), lowmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ (bottom left) and highmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ (bottom right) searches. The pNNs are evaluated at the mass points where the largest excess with respect to the backgroundonly hypothesis is observed. If the MC simulation at this mass point is not available, then the sample produced at a mass point closest to the excess is shown. The filled histograms represent the background simulation, and the data are shown by the black points. The ``H'' process includes ggH, VBF, VH, and $ {\mathrm{t}\overline{\mathrm{t}}} $H. The targeted signal distributions for which the pNN is evaluated are shown by the black unfilled histograms. The background MC simulation is normalized to data and the signal is normalized to an arbitrary cross section for representation purposes. The ratio of the data to the sum of the background predictions is shown in the lower panel. Statistical MC uncertainties for the background are represented by the greyshaded bands. 
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Figure 5d:
Transformed output of the pNNs used in the $ \mathrm{X}^{(0)} \to \mathrm{H}\mathrm{H} $ (top left), $ \mathrm{X}^{(2)} \to \mathrm{H}\mathrm{H} $ (top right), $ \mathrm{X} \to \mathrm{Y}(\tau\tau)\mathrm{H}(\gamma\gamma) $ (middle), lowmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ (bottom left) and highmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ (bottom right) searches. The pNNs are evaluated at the mass points where the largest excess with respect to the backgroundonly hypothesis is observed. If the MC simulation at this mass point is not available, then the sample produced at a mass point closest to the excess is shown. The filled histograms represent the background simulation, and the data are shown by the black points. The ``H'' process includes ggH, VBF, VH, and $ {\mathrm{t}\overline{\mathrm{t}}} $H. The targeted signal distributions for which the pNN is evaluated are shown by the black unfilled histograms. The background MC simulation is normalized to data and the signal is normalized to an arbitrary cross section for representation purposes. The ratio of the data to the sum of the background predictions is shown in the lower panel. Statistical MC uncertainties for the background are represented by the greyshaded bands. 
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Figure 5e:
Transformed output of the pNNs used in the $ \mathrm{X}^{(0)} \to \mathrm{H}\mathrm{H} $ (top left), $ \mathrm{X}^{(2)} \to \mathrm{H}\mathrm{H} $ (top right), $ \mathrm{X} \to \mathrm{Y}(\tau\tau)\mathrm{H}(\gamma\gamma) $ (middle), lowmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ (bottom left) and highmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ (bottom right) searches. The pNNs are evaluated at the mass points where the largest excess with respect to the backgroundonly hypothesis is observed. If the MC simulation at this mass point is not available, then the sample produced at a mass point closest to the excess is shown. The filled histograms represent the background simulation, and the data are shown by the black points. The ``H'' process includes ggH, VBF, VH, and $ {\mathrm{t}\overline{\mathrm{t}}} $H. The targeted signal distributions for which the pNN is evaluated are shown by the black unfilled histograms. The background MC simulation is normalized to data and the signal is normalized to an arbitrary cross section for representation purposes. The ratio of the data to the sum of the background predictions is shown in the lower panel. Statistical MC uncertainties for the background are represented by the greyshaded bands. 
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Figure 6:
Signal pdfs for the nonresonant search analysis categories, shown for each year of simulated data, and for the sum of all years together. The pdfs are normalized to 25 times the expected event yields in the SM. The open squares represent the weighted simulation events and the blue line is the corresponding pdf. The grey shaded areas correspond to the $ \sigma_{\rm{eff}} $, defined as half the width of the narrowest interval containing 68.3% of the $ m_{\gamma\gamma} $ distribution. The contribution from each year of datataking is illustrated with the dotted lines. 
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Figure 6a:
Signal pdfs for the nonresonant search analysis categories, shown for each year of simulated data, and for the sum of all years together. The pdfs are normalized to 25 times the expected event yields in the SM. The open squares represent the weighted simulation events and the blue line is the corresponding pdf. The grey shaded areas correspond to the $ \sigma_{\rm{eff}} $, defined as half the width of the narrowest interval containing 68.3% of the $ m_{\gamma\gamma} $ distribution. The contribution from each year of datataking is illustrated with the dotted lines. 
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Figure 6b:
Signal pdfs for the nonresonant search analysis categories, shown for each year of simulated data, and for the sum of all years together. The pdfs are normalized to 25 times the expected event yields in the SM. The open squares represent the weighted simulation events and the blue line is the corresponding pdf. The grey shaded areas correspond to the $ \sigma_{\rm{eff}} $, defined as half the width of the narrowest interval containing 68.3% of the $ m_{\gamma\gamma} $ distribution. The contribution from each year of datataking is illustrated with the dotted lines. 
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Figure 7:
Signal efficiency, $ \epsilon $, and interpolated DCB shape parameters, $ \Delta m_{\gamma\gamma} $ and $ \sigma $, for the highest purity analysis category in the $ \mathrm{X}^{(2)} \to \mathrm{H}\mathrm{H} $ search, as functions of $ m_{\mathrm{X}} $ (left). The first shape parameter, $ \Delta m_{\gamma\gamma} $, is defined as $ \overline{m}_{\gamma\gamma} $ 125. Signal efficiency in the ($ m_{\mathrm{X}} $,$ m_{\mathrm{Y}} $) plane for the highest purity analysis category in the $ \mathrm{X} \to \mathrm{Y}(\tau\tau)\mathrm{H}(\gamma\gamma) $ search (right). 
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Figure 7a:
Signal efficiency, $ \epsilon $, and interpolated DCB shape parameters, $ \Delta m_{\gamma\gamma} $ and $ \sigma $, for the highest purity analysis category in the $ \mathrm{X}^{(2)} \to \mathrm{H}\mathrm{H} $ search, as functions of $ m_{\mathrm{X}} $ (left). The first shape parameter, $ \Delta m_{\gamma\gamma} $, is defined as $ \overline{m}_{\gamma\gamma} $ 125. Signal efficiency in the ($ m_{\mathrm{X}} $,$ m_{\mathrm{Y}} $) plane for the highest purity analysis category in the $ \mathrm{X} \to \mathrm{Y}(\tau\tau)\mathrm{H}(\gamma\gamma) $ search (right). 
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Figure 7b:
Signal efficiency, $ \epsilon $, and interpolated DCB shape parameters, $ \Delta m_{\gamma\gamma} $ and $ \sigma $, for the highest purity analysis category in the $ \mathrm{X}^{(2)} \to \mathrm{H}\mathrm{H} $ search, as functions of $ m_{\mathrm{X}} $ (left). The first shape parameter, $ \Delta m_{\gamma\gamma} $, is defined as $ \overline{m}_{\gamma\gamma} $ 125. Signal efficiency in the ($ m_{\mathrm{X}} $,$ m_{\mathrm{Y}} $) plane for the highest purity analysis category in the $ \mathrm{X} \to \mathrm{Y}(\tau\tau)\mathrm{H}(\gamma\gamma) $ search (right). 
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Figure 8:
Data points (black) and signalplusbackground models for the most sensitive analysis category in each search channel are shown: nonresonant (top left), $ \mathrm{X}^{(0)} \to \mathrm{H}\mathrm{H} $ (top right), $ \mathrm{X}^{(2)} \to \mathrm{H}\mathrm{H} $ (middle left), $ \mathrm{X} \to \mathrm{Y}(\tau\tau)\mathrm{H}(\gamma\gamma) $ (middle right), lowmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ (bottom left) and the highmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ (bottom right). The analysis categories for the resonant search channels correspond to the mass hypotheses where the largest excesses with respect to the backgroundonly hypothesis are observed. The one (green) standard deviation and two (yellow) standard deviation bands show the uncertainties in the background component of the fit. The solid red line shows the sum of the fitted signal and background components, the solid blue line shows the continuum background and the background from single H production together, and the dashed black line shows only the continuum background component. The lower panel in each plot shows the residual signal yield after subtraction of the background. 
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Figure 8a:
Data points (black) and signalplusbackground models for the most sensitive analysis category in each search channel are shown: nonresonant (top left), $ \mathrm{X}^{(0)} \to \mathrm{H}\mathrm{H} $ (top right), $ \mathrm{X}^{(2)} \to \mathrm{H}\mathrm{H} $ (middle left), $ \mathrm{X} \to \mathrm{Y}(\tau\tau)\mathrm{H}(\gamma\gamma) $ (middle right), lowmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ (bottom left) and the highmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ (bottom right). The analysis categories for the resonant search channels correspond to the mass hypotheses where the largest excesses with respect to the backgroundonly hypothesis are observed. The one (green) standard deviation and two (yellow) standard deviation bands show the uncertainties in the background component of the fit. The solid red line shows the sum of the fitted signal and background components, the solid blue line shows the continuum background and the background from single H production together, and the dashed black line shows only the continuum background component. The lower panel in each plot shows the residual signal yield after subtraction of the background. 
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Figure 8b:
Data points (black) and signalplusbackground models for the most sensitive analysis category in each search channel are shown: nonresonant (top left), $ \mathrm{X}^{(0)} \to \mathrm{H}\mathrm{H} $ (top right), $ \mathrm{X}^{(2)} \to \mathrm{H}\mathrm{H} $ (middle left), $ \mathrm{X} \to \mathrm{Y}(\tau\tau)\mathrm{H}(\gamma\gamma) $ (middle right), lowmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ (bottom left) and the highmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ (bottom right). The analysis categories for the resonant search channels correspond to the mass hypotheses where the largest excesses with respect to the backgroundonly hypothesis are observed. The one (green) standard deviation and two (yellow) standard deviation bands show the uncertainties in the background component of the fit. The solid red line shows the sum of the fitted signal and background components, the solid blue line shows the continuum background and the background from single H production together, and the dashed black line shows only the continuum background component. The lower panel in each plot shows the residual signal yield after subtraction of the background. 
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Figure 8c:
Data points (black) and signalplusbackground models for the most sensitive analysis category in each search channel are shown: nonresonant (top left), $ \mathrm{X}^{(0)} \to \mathrm{H}\mathrm{H} $ (top right), $ \mathrm{X}^{(2)} \to \mathrm{H}\mathrm{H} $ (middle left), $ \mathrm{X} \to \mathrm{Y}(\tau\tau)\mathrm{H}(\gamma\gamma) $ (middle right), lowmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ (bottom left) and the highmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ (bottom right). The analysis categories for the resonant search channels correspond to the mass hypotheses where the largest excesses with respect to the backgroundonly hypothesis are observed. The one (green) standard deviation and two (yellow) standard deviation bands show the uncertainties in the background component of the fit. The solid red line shows the sum of the fitted signal and background components, the solid blue line shows the continuum background and the background from single H production together, and the dashed black line shows only the continuum background component. The lower panel in each plot shows the residual signal yield after subtraction of the background. 
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Figure 8d:
Data points (black) and signalplusbackground models for the most sensitive analysis category in each search channel are shown: nonresonant (top left), $ \mathrm{X}^{(0)} \to \mathrm{H}\mathrm{H} $ (top right), $ \mathrm{X}^{(2)} \to \mathrm{H}\mathrm{H} $ (middle left), $ \mathrm{X} \to \mathrm{Y}(\tau\tau)\mathrm{H}(\gamma\gamma) $ (middle right), lowmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ (bottom left) and the highmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ (bottom right). The analysis categories for the resonant search channels correspond to the mass hypotheses where the largest excesses with respect to the backgroundonly hypothesis are observed. The one (green) standard deviation and two (yellow) standard deviation bands show the uncertainties in the background component of the fit. The solid red line shows the sum of the fitted signal and background components, the solid blue line shows the continuum background and the background from single H production together, and the dashed black line shows only the continuum background component. The lower panel in each plot shows the residual signal yield after subtraction of the background. 
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Figure 8e:
Data points (black) and signalplusbackground models for the most sensitive analysis category in each search channel are shown: nonresonant (top left), $ \mathrm{X}^{(0)} \to \mathrm{H}\mathrm{H} $ (top right), $ \mathrm{X}^{(2)} \to \mathrm{H}\mathrm{H} $ (middle left), $ \mathrm{X} \to \mathrm{Y}(\tau\tau)\mathrm{H}(\gamma\gamma) $ (middle right), lowmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ (bottom left) and the highmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ (bottom right). The analysis categories for the resonant search channels correspond to the mass hypotheses where the largest excesses with respect to the backgroundonly hypothesis are observed. The one (green) standard deviation and two (yellow) standard deviation bands show the uncertainties in the background component of the fit. The solid red line shows the sum of the fitted signal and background components, the solid blue line shows the continuum background and the background from single H production together, and the dashed black line shows only the continuum background component. The lower panel in each plot shows the residual signal yield after subtraction of the background. 
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Figure 8f:
Data points (black) and signalplusbackground models for the most sensitive analysis category in each search channel are shown: nonresonant (top left), $ \mathrm{X}^{(0)} \to \mathrm{H}\mathrm{H} $ (top right), $ \mathrm{X}^{(2)} \to \mathrm{H}\mathrm{H} $ (middle left), $ \mathrm{X} \to \mathrm{Y}(\tau\tau)\mathrm{H}(\gamma\gamma) $ (middle right), lowmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ (bottom left) and the highmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ (bottom right). The analysis categories for the resonant search channels correspond to the mass hypotheses where the largest excesses with respect to the backgroundonly hypothesis are observed. The one (green) standard deviation and two (yellow) standard deviation bands show the uncertainties in the background component of the fit. The solid red line shows the sum of the fitted signal and background components, the solid blue line shows the continuum background and the background from single H production together, and the dashed black line shows only the continuum background component. The lower panel in each plot shows the residual signal yield after subtraction of the background. 
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Figure 9:
Expected and observed upper limits on the nonresonant HH production cross section at the 95% CL, obtained for different values of $ \kappa_\lambda $. The green and yellow bands represent the one and two standard deviations for the expected limit, respectively. The theoretical prediction with the uncertainty of the cross section as a function of $ \kappa_\lambda $ is shown by the red band. 
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Figure 10:
Expected and observed upper limits on the nonresonant HH production cross section at the 95% CL, for different thirteen BSM benchmark scenarios which consider different values of the couplings, $ \kappa_\lambda $, $ \kappa_\mathrm{t} $, $ c_{2\mathrm{g}} $, $ c_{\mathrm{g}} $ and $ c_2 $ (defined in Table 1). The green and yellow bands represent the one and two standard deviations for the expected limits, respectively. 
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Figure 11:
Expected and observed 95% CL upper limit on the resonant production cross section, $ \sigma({\rm{pp}} \to \mathrm{X} \to \mathrm{H}\mathrm{H}) $ for the spin0 $ \mathrm{X}^{(0)} \to \mathrm{H}\mathrm{H} $ search (top) and spin2 $ \mathrm{X}^{(2)} \to \mathrm{H}\mathrm{H} $ search (bottom). The dashed and solid black lines represent the expected and observed limits, respectively. The green and yellow bands represent the one and two standard deviations for the expected limit, respectively. The red lines show the theoretical predictions with different energy scales and couplings [82]. 
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Figure 11a:
Expected and observed 95% CL upper limit on the resonant production cross section, $ \sigma({\rm{pp}} \to \mathrm{X} \to \mathrm{H}\mathrm{H}) $ for the spin0 $ \mathrm{X}^{(0)} \to \mathrm{H}\mathrm{H} $ search (top) and spin2 $ \mathrm{X}^{(2)} \to \mathrm{H}\mathrm{H} $ search (bottom). The dashed and solid black lines represent the expected and observed limits, respectively. The green and yellow bands represent the one and two standard deviations for the expected limit, respectively. The red lines show the theoretical predictions with different energy scales and couplings [82]. 
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Figure 11b:
Expected and observed 95% CL upper limit on the resonant production cross section, $ \sigma({\rm{pp}} \to \mathrm{X} \to \mathrm{H}\mathrm{H}) $ for the spin0 $ \mathrm{X}^{(0)} \to \mathrm{H}\mathrm{H} $ search (top) and spin2 $ \mathrm{X}^{(2)} \to \mathrm{H}\mathrm{H} $ search (bottom). The dashed and solid black lines represent the expected and observed limits, respectively. The green and yellow bands represent the one and two standard deviations for the expected limit, respectively. The red lines show the theoretical predictions with different energy scales and couplings [82]. 
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Figure 12:
The top plot shows the expected and observed 95% CL upper limit on $ \sigma({\rm{pp}} \to \mathrm{X} \to \mathrm{Y}\mathrm{H} \to \gamma\gamma\tau\tau) $ for the $ \mathrm{X} \to \mathrm{Y}(\tau\tau)\mathrm{H}(\gamma\gamma) $ search. The dashed and solid black lines represent the expected and observed limits, respectively. The green and yellow bands represent the one and two standard deviations for the expected limit, respectively. Limits are scaled by orders of 10, labeled in the plot, depending on $ m_{\mathrm{X}} $ (left) or $ m_{\mathrm{Y}} $ (right). The bottom plot shows the observed upper limits in the 2D ($ m_{\mathrm{X}} $,$ m_{\mathrm{Y}} $) plane. The values of the limits are shown by the colour scale. 
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Figure 12a:
The top plot shows the expected and observed 95% CL upper limit on $ \sigma({\rm{pp}} \to \mathrm{X} \to \mathrm{Y}\mathrm{H} \to \gamma\gamma\tau\tau) $ for the $ \mathrm{X} \to \mathrm{Y}(\tau\tau)\mathrm{H}(\gamma\gamma) $ search. The dashed and solid black lines represent the expected and observed limits, respectively. The green and yellow bands represent the one and two standard deviations for the expected limit, respectively. Limits are scaled by orders of 10, labeled in the plot, depending on $ m_{\mathrm{X}} $ (left) or $ m_{\mathrm{Y}} $ (right). The bottom plot shows the observed upper limits in the 2D ($ m_{\mathrm{X}} $,$ m_{\mathrm{Y}} $) plane. The values of the limits are shown by the colour scale. 
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Figure 12b:
The top plot shows the expected and observed 95% CL upper limit on $ \sigma({\rm{pp}} \to \mathrm{X} \to \mathrm{Y}\mathrm{H} \to \gamma\gamma\tau\tau) $ for the $ \mathrm{X} \to \mathrm{Y}(\tau\tau)\mathrm{H}(\gamma\gamma) $ search. The dashed and solid black lines represent the expected and observed limits, respectively. The green and yellow bands represent the one and two standard deviations for the expected limit, respectively. Limits are scaled by orders of 10, labeled in the plot, depending on $ m_{\mathrm{X}} $ (left) or $ m_{\mathrm{Y}} $ (right). The bottom plot shows the observed upper limits in the 2D ($ m_{\mathrm{X}} $,$ m_{\mathrm{Y}} $) plane. The values of the limits are shown by the colour scale. 
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Figure 12c:
The top plot shows the expected and observed 95% CL upper limit on $ \sigma({\rm{pp}} \to \mathrm{X} \to \mathrm{Y}\mathrm{H} \to \gamma\gamma\tau\tau) $ for the $ \mathrm{X} \to \mathrm{Y}(\tau\tau)\mathrm{H}(\gamma\gamma) $ search. The dashed and solid black lines represent the expected and observed limits, respectively. The green and yellow bands represent the one and two standard deviations for the expected limit, respectively. Limits are scaled by orders of 10, labeled in the plot, depending on $ m_{\mathrm{X}} $ (left) or $ m_{\mathrm{Y}} $ (right). The bottom plot shows the observed upper limits in the 2D ($ m_{\mathrm{X}} $,$ m_{\mathrm{Y}} $) plane. The values of the limits are shown by the colour scale. 
png pdf 
Figure 13:
The top plot shows the expected and observed 95% CL upper limit on $ \sigma({\rm{pp}} \to \mathrm{X} \to \mathrm{Y}\mathrm{H})B(\mathrm{Y} \to \gamma\gamma) $ for the lowmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ search. The dashed and solid black lines represent the expected and observed limits, respectively. The green and yellow bands represent the one and two standard deviations for the expected limit, respectively. Limits are scaled by orders of 10, labeled in the plot, depending on $ m_{\mathrm{X}} $ (left) or $ m_{\mathrm{Y}} $ (right). The bottom plot shows the observed upper limits in the 2D ($ m_{\mathrm{X}} $,$ m_{\mathrm{Y}} $) plane. The values of the limits are shown by the colour scale. The redhatched region indicates masses for which the observed limits are below the maximally allowed limits in the NMSSM taken from Ref. [83]. 
png pdf 
Figure 13a:
The top plot shows the expected and observed 95% CL upper limit on $ \sigma({\rm{pp}} \to \mathrm{X} \to \mathrm{Y}\mathrm{H})B(\mathrm{Y} \to \gamma\gamma) $ for the lowmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ search. The dashed and solid black lines represent the expected and observed limits, respectively. The green and yellow bands represent the one and two standard deviations for the expected limit, respectively. Limits are scaled by orders of 10, labeled in the plot, depending on $ m_{\mathrm{X}} $ (left) or $ m_{\mathrm{Y}} $ (right). The bottom plot shows the observed upper limits in the 2D ($ m_{\mathrm{X}} $,$ m_{\mathrm{Y}} $) plane. The values of the limits are shown by the colour scale. The redhatched region indicates masses for which the observed limits are below the maximally allowed limits in the NMSSM taken from Ref. [83]. 
png pdf 
Figure 13b:
The top plot shows the expected and observed 95% CL upper limit on $ \sigma({\rm{pp}} \to \mathrm{X} \to \mathrm{Y}\mathrm{H})B(\mathrm{Y} \to \gamma\gamma) $ for the lowmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ search. The dashed and solid black lines represent the expected and observed limits, respectively. The green and yellow bands represent the one and two standard deviations for the expected limit, respectively. Limits are scaled by orders of 10, labeled in the plot, depending on $ m_{\mathrm{X}} $ (left) or $ m_{\mathrm{Y}} $ (right). The bottom plot shows the observed upper limits in the 2D ($ m_{\mathrm{X}} $,$ m_{\mathrm{Y}} $) plane. The values of the limits are shown by the colour scale. The redhatched region indicates masses for which the observed limits are below the maximally allowed limits in the NMSSM taken from Ref. [83]. 
png 
Figure 13c:
The top plot shows the expected and observed 95% CL upper limit on $ \sigma({\rm{pp}} \to \mathrm{X} \to \mathrm{Y}\mathrm{H})B(\mathrm{Y} \to \gamma\gamma) $ for the lowmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ search. The dashed and solid black lines represent the expected and observed limits, respectively. The green and yellow bands represent the one and two standard deviations for the expected limit, respectively. Limits are scaled by orders of 10, labeled in the plot, depending on $ m_{\mathrm{X}} $ (left) or $ m_{\mathrm{Y}} $ (right). The bottom plot shows the observed upper limits in the 2D ($ m_{\mathrm{X}} $,$ m_{\mathrm{Y}} $) plane. The values of the limits are shown by the colour scale. The redhatched region indicates masses for which the observed limits are below the maximally allowed limits in the NMSSM taken from Ref. [83]. 
png pdf 
Figure 14:
The top plot shows the expected and observed 95% CL upper limit on $ \sigma({\rm{pp}} \to \mathrm{X} \to \mathrm{Y}\mathrm{H})B(\mathrm{Y} \to \gamma\gamma) $ for the highmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ search. The dashed and solid black lines represent the expected and observed limits, respectively. The green and yellow bands represent the one and two standard deviations for the expected limit, respectively. Limits are scaled by orders of 100 (left) or 10 (right), labeled in the plot, depending on $ m_{\mathrm{X}} $ (left) or $ m_{\mathrm{Y}} $ (right). In the topleft plot, there is a discontinuity in the limits for $ m_{\mathrm{X}}= $ 650 GeV which is due to the chosen limit granularity in $ m_{\mathrm{X}} $ and $ m_{\mathrm{Y}} $. For the range $ m_{\mathrm{Y}}\in[274, 388]\,\text{Ge\hspace{.08em}V} $, there are limits placed at $ m_{\mathrm{X}}= $ 600, 633, 666 and 700 GeV instead of 600, 650 and 700 GeV. The bottom plot shows the observed upper limits in the 2D ($ m_{\mathrm{X}} $,$ m_{\mathrm{Y}} $) plane. The values of the limits are shown by the colour scale. 
png pdf 
Figure 14a:
The top plot shows the expected and observed 95% CL upper limit on $ \sigma({\rm{pp}} \to \mathrm{X} \to \mathrm{Y}\mathrm{H})B(\mathrm{Y} \to \gamma\gamma) $ for the highmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ search. The dashed and solid black lines represent the expected and observed limits, respectively. The green and yellow bands represent the one and two standard deviations for the expected limit, respectively. Limits are scaled by orders of 100 (left) or 10 (right), labeled in the plot, depending on $ m_{\mathrm{X}} $ (left) or $ m_{\mathrm{Y}} $ (right). In the topleft plot, there is a discontinuity in the limits for $ m_{\mathrm{X}}= $ 650 GeV which is due to the chosen limit granularity in $ m_{\mathrm{X}} $ and $ m_{\mathrm{Y}} $. For the range $ m_{\mathrm{Y}}\in[274, 388]\,\text{Ge\hspace{.08em}V} $, there are limits placed at $ m_{\mathrm{X}}= $ 600, 633, 666 and 700 GeV instead of 600, 650 and 700 GeV. The bottom plot shows the observed upper limits in the 2D ($ m_{\mathrm{X}} $,$ m_{\mathrm{Y}} $) plane. The values of the limits are shown by the colour scale. 
png pdf 
Figure 14b:
The top plot shows the expected and observed 95% CL upper limit on $ \sigma({\rm{pp}} \to \mathrm{X} \to \mathrm{Y}\mathrm{H})B(\mathrm{Y} \to \gamma\gamma) $ for the highmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ search. The dashed and solid black lines represent the expected and observed limits, respectively. The green and yellow bands represent the one and two standard deviations for the expected limit, respectively. Limits are scaled by orders of 100 (left) or 10 (right), labeled in the plot, depending on $ m_{\mathrm{X}} $ (left) or $ m_{\mathrm{Y}} $ (right). In the topleft plot, there is a discontinuity in the limits for $ m_{\mathrm{X}}= $ 650 GeV which is due to the chosen limit granularity in $ m_{\mathrm{X}} $ and $ m_{\mathrm{Y}} $. For the range $ m_{\mathrm{Y}}\in[274, 388]\,\text{Ge\hspace{.08em}V} $, there are limits placed at $ m_{\mathrm{X}}= $ 600, 633, 666 and 700 GeV instead of 600, 650 and 700 GeV. The bottom plot shows the observed upper limits in the 2D ($ m_{\mathrm{X}} $,$ m_{\mathrm{Y}} $) plane. The values of the limits are shown by the colour scale. 
png 
Figure 14c:
The top plot shows the expected and observed 95% CL upper limit on $ \sigma({\rm{pp}} \to \mathrm{X} \to \mathrm{Y}\mathrm{H})B(\mathrm{Y} \to \gamma\gamma) $ for the highmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ search. The dashed and solid black lines represent the expected and observed limits, respectively. The green and yellow bands represent the one and two standard deviations for the expected limit, respectively. Limits are scaled by orders of 100 (left) or 10 (right), labeled in the plot, depending on $ m_{\mathrm{X}} $ (left) or $ m_{\mathrm{Y}} $ (right). In the topleft plot, there is a discontinuity in the limits for $ m_{\mathrm{X}}= $ 650 GeV which is due to the chosen limit granularity in $ m_{\mathrm{X}} $ and $ m_{\mathrm{Y}} $. For the range $ m_{\mathrm{Y}}\in[274, 388]\,\text{Ge\hspace{.08em}V} $, there are limits placed at $ m_{\mathrm{X}}= $ 600, 633, 666 and 700 GeV instead of 600, 650 and 700 GeV. The bottom plot shows the observed upper limits in the 2D ($ m_{\mathrm{X}} $,$ m_{\mathrm{Y}} $) plane. The values of the limits are shown by the colour scale. 
Tables  
png pdf 
Table 1:
Parameter values of nonresonant BSM benchmark hypotheses. The first column corresponds to the SM sample, while the next 13 correspond to the benchmark hypotheses identified using the method from Refs. [24,25]. 
png pdf 
Table 2:
Additional photon requirements for barrel and endcap photons at different ranges of $ R_\mathrm{9} $, intended to mimic the HLT requirements. 
png pdf 
Table 3:
Number of expected events in each category for each analysis. There is one last category in addition to the ones shown here that contains the remainder of the events. 
Summary 
A search for the production of two scalar bosons in the $ \gamma\gamma\tau\tau $ final state is presented. The search uses data from protonproton collisions collected by the CMS experiment at the LHC in 20162018 at a centreofmass energy of 13 TeV, corresponding to 138 fb$ ^{1} $ of integrated luminosity. In total, five search channels are considered. One channel targets the nonresonant HH production via gluonfusion, where no significant deviation from the backgroundonly hypothesis is observed. Upper limits at the 95% CL on the HH production cross section are extracted for production in the SM and in several BSM scenarios. The observed upper limit for the SM production is found to be 930 fb, corresponding to 33 times the SM prediction, whilst the expected upper limit is 740 fb, corresponding to 26 times the SM prediction. The limit is also derived as a function of the Higgs boson selfcoupling modifier, $ \kappa_\lambda $, assuming all other Higgs boson couplings are as predicted in the SM. The selfcoupling modifier, $ \kappa_\lambda $, is constrained within the range $ $13 $ < \kappa_\lambda < $ 18 at the 95% CL. In addition, the limit is extracted for numerous BSM benchmark scenarios. The results are consistent with the SM predictions. This analysis also targets the resonant production of two scalar bosons. Two channels are constructed to search for a resonance X decaying to a SM Higgs boson pair, $ \mathrm{X} \to \mathrm{H}\mathrm{H} $, for both the spin0 resonance and spin2 resonance scenarios. No significant deviation from the backgroundonly hypothesis is observed. Furthermore, the analysis targets the $ \mathrm{X} \to \mathrm{Y}\mathrm{H} $ process, where Y is an additional, lighter (than X) scalar particle. Three search channels are constructed, namely the $ \mathrm{X} \to \mathrm{Y}(\tau\tau)\mathrm{H}(\gamma\gamma) $, lowmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ and highmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ channels, which target the different decay chains in different mass regimes. The largest local significance across these channels is 3.4 standard deviations, which once considering the lookelsewhere effect, has a global significance of 0.1 standard deviations. Therefore, this analysis, as a standalone result, does not present any significant deviation from the standard model. However, when put into the context of recent excesses in CMS at resonance masses of 650 GeV and 95 GeV, the local significance of 2.3 at $ m_{\mathrm{X}} = $ 650 GeV and $ m_{\mathrm{Y}}= $ 95 GeV in the lowmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ analysis is interesting and warrants further measurements. 
Additional Figures  
png pdf 
Additional Figure 1:
Profile likelihood scan as a function of $ \kappa_\lambda $ for the observed data (black solid line). The expected result (red dashed line) assuming the SM hypothesis, derived from an Asimov data set with $ \kappa_\lambda = $ 1 is also shown. The bestfit values and 68% CL intervals for $ \kappa_\lambda $ from the observed and expected scans are shown in the legend. 
png pdf 
Additional Figure 2:
Local significances of signals in the 2D ($ m_{\mathrm{X}} $,$ m_{\mathrm{Y}} $) plane in the highmass $ \mathrm{X} \to \mathrm{Y}(\tau\tau)\mathrm{H}(\gamma\gamma) $ search. The values of significance are shown by the colour scale. 
png pdf 
Additional Figure 3:
Local significances of signals in the 2D ($ m_{\mathrm{X}} $,$ m_{\mathrm{Y}} $) plane in the lowmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ search. The values of significance are shown by the colour scale. 
png pdf 
Additional Figure 4:
Local significances of signals in the 2D ($ m_{\mathrm{X}} $,$ m_{\mathrm{Y}} $) plane in the highmass $ \mathrm{X} \to \mathrm{Y}(\gamma\gamma)\mathrm{H}(\tau\tau) $ search. The values of significance are shown by the colour scale. 
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