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| CMS-PAS-HIG-20-002 | ||
| Search for a standard model-like Higgs boson in the mass range between 70 and 110 GeV in the diphoton final state in proton-proton collisions at $ \sqrt{s}= $ 13 TeV | ||
| CMS Collaboration | ||
| 20 March 2023 | ||
| Abstract: The results of a search for a standard model-like Higgs boson in the mass range between 70 and 110 GeV decaying into two photons are presented. The analysis uses the data set collected with the CMS experiment in proton-proton collisions corresponding to, respectively, 36.3 fb$ ^{-1} $, 41.5 fb$ ^{-1} $ and 54.4 fb$ ^{-1} $, during the 2016, 2017 and 2018 LHC running periods, at $ \sqrt{s}= $ 13 TeV. The expected and observed 95% confidence level upper limits on the product of the cross section and branching fraction into two photons are presented. The observed upper limit for the combined data set ranges from 73 fb to 15 fb. | ||
| Links: CDS record (PDF) ; CADI line (restricted) ; | ||
| Figures & Tables | Summary | Additional Figures | References | CMS Publications |
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| Figures | |
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Figure 1:
Full parameterized signal shape, integrated over all event classes, in simulated signal events with $ m_{\mathrm{H}}= $ 90 GeV for 2016 (top left), 2017(top right) and 2018 (bottom). The open points are the weighted MC events and the blue lines the corresponding parametric models. Also shown are the $ \sigma_{\text{eff}} $ values and the shaded region limited by $ \pm\sigma_{\text{eff}} $, along with the FWHM values, indicated by the position of the arrows on each distribution. |
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Figure 1-a:
Full parameterized signal shape, integrated over all event classes, in simulated signal events with $ m_{\mathrm{H}}= $ 90 GeV for 2016. The open points are the weighted MC events and the blue lines the corresponding parametric models. Also shown are the $ \sigma_{\text{eff}} $ values and the shaded region limited by $ \pm\sigma_{\text{eff}} $, along with the FWHM values, indicated by the position of the arrows. |
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Figure 1-b:
Full parameterized signal shape, integrated over all event classes, in simulated signal events with $ m_{\mathrm{H}}= $ 90 GeV for 2017. The open points are the weighted MC events and the blue lines the corresponding parametric models. Also shown are the $ \sigma_{\text{eff}} $ values and the shaded region limited by $ \pm\sigma_{\text{eff}} $, along with the FWHM values, indicated by the position of the arrows. |
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Figure 1-c:
Full parameterized signal shape, integrated over all event classes, in simulated signal events with $ m_{\mathrm{H}}= $ 90 GeV for 2018. The open points are the weighted MC events and the blue lines the corresponding parametric models. Also shown are the $ \sigma_{\text{eff}} $ values and the shaded region limited by $ \pm\sigma_{\text{eff}} $, along with the FWHM values, indicated by the position of the arrows. |
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Figure 2:
Background model fits using the chosen ``best-fit" parametrization to the 2016 data in the three event classes. The corresponding signal model for each class for $ m_{\mathrm{H}}= $ 90 GeV, multiplied by 10, is also shown. The one- and two-$ \sigma $ bands reflect the uncertainty in the background model normalization associated with the statistical uncertainties of the fits, and are shown for illustration purposes only. The difference between the data and the best-fit model is shown in the lower panels. |
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Figure 2-a:
Background model fits using the chosen ``best-fit" parametrization to the 2016 data in the event class 0. The corresponding signal model for each class for $ m_{\mathrm{H}}= $ 90 GeV, multiplied by 10, is also shown. The one- and two-$ \sigma $ bands reflect the uncertainty in the background model normalization associated with the statistical uncertainties of the fits, and are shown for illustration purposes only. The difference between the data and the best-fit model is shown in the lower panel. |
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Figure 2-b:
Background model fits using the chosen ``best-fit" parametrization to the 2016 data in the event class 1. The corresponding signal model for each class for $ m_{\mathrm{H}}= $ 90 GeV, multiplied by 10, is also shown. The one- and two-$ \sigma $ bands reflect the uncertainty in the background model normalization associated with the statistical uncertainties of the fits, and are shown for illustration purposes only. The difference between the data and the best-fit model is shown in the lower panel. |
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Figure 2-c:
Background model fits using the chosen ``best-fit" parametrization to the 2016 data in the event class 2. The corresponding signal model for each class for $ m_{\mathrm{H}}= $ 90 GeV, multiplied by 10, is also shown. The one- and two-$ \sigma $ bands reflect the uncertainty in the background model normalization associated with the statistical uncertainties of the fits, and are shown for illustration purposes only. The difference between the data and the best-fit model is shown in the lower panel. |
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Figure 3:
Background model fits using the chosen ``best-fit" parametrization to the 2017 data in the four event classes. The corresponding signal model for each class for $ m_{\mathrm{H}}= $ 90 GeV, multiplied by 10, is also shown. The one- and two-$ \sigma $ bands reflect the uncertainty in the background model normalization associated with the statistical uncertainties of the fits, and are shown for illustration purposes only. The difference between the data and the best-fit model is shown in the lower panels. |
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Figure 3-a:
Background model fits using the chosen ``best-fit" parametrization to the 2017 data in the event class 0. The corresponding signal model for each class for $ m_{\mathrm{H}}= $ 90 GeV, multiplied by 10, is also shown. The one- and two-$ \sigma $ bands reflect the uncertainty in the background model normalization associated with the statistical uncertainties of the fits, and are shown for illustration purposes only. The difference between the data and the best-fit model is shown in the lower panel. |
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Figure 3-b:
Background model fits using the chosen ``best-fit" parametrization to the 2017 data in the event class 1. The corresponding signal model for each class for $ m_{\mathrm{H}}= $ 90 GeV, multiplied by 10, is also shown. The one- and two-$ \sigma $ bands reflect the uncertainty in the background model normalization associated with the statistical uncertainties of the fits, and are shown for illustration purposes only. The difference between the data and the best-fit model is shown in the lower panel. |
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Figure 3-c:
Background model fits using the chosen ``best-fit" parametrization to the 2017 data in the event class 2. The corresponding signal model for each class for $ m_{\mathrm{H}}= $ 90 GeV, multiplied by 10, is also shown. The one- and two-$ \sigma $ bands reflect the uncertainty in the background model normalization associated with the statistical uncertainties of the fits, and are shown for illustration purposes only. The difference between the data and the best-fit model is shown in the lower panel. |
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Figure 3-d:
Background model fits using the chosen ``best-fit" parametrization to the 2017 data in the VBF event class. The corresponding signal model for each class for $ m_{\mathrm{H}}= $ 90 GeV, multiplied by 10, is also shown. The one- and two-$ \sigma $ bands reflect the uncertainty in the background model normalization associated with the statistical uncertainties of the fits, and are shown for illustration purposes only. The difference between the data and the best-fit model is shown in the lower panel. |
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Figure 4:
Background model fits using the chosen ``best-fit" parametrization to the 2018 data in the four event classes. The corresponding signal model for each class for $ m_{\mathrm{H}}= $ 90 GeV, multiplied by 10, is also shown. The one- and two-$ \sigma $ bands reflect the uncertainty in the background model normalization associated with the statistical uncertainties of the fits, and are shown for illustration purposes only. The difference between the data and the best-fit model is shown in the lower panels. |
png pdf |
Figure 4-a:
Background model fits using the chosen ``best-fit" parametrization to the 2018 data in event class 0. The corresponding signal model for each class for $ m_{\mathrm{H}}= $ 90 GeV, multiplied by 10, is also shown. The one- and two-$ \sigma $ bands reflect the uncertainty in the background model normalization associated with the statistical uncertainties of the fits, and are shown for illustration purposes only. The difference between the data and the best-fit model is shown in the lower panel. |
png pdf |
Figure 4-b:
Background model fits using the chosen ``best-fit" parametrization to the 2018 data in event class 1. The corresponding signal model for each class for $ m_{\mathrm{H}}= $ 90 GeV, multiplied by 10, is also shown. The one- and two-$ \sigma $ bands reflect the uncertainty in the background model normalization associated with the statistical uncertainties of the fits, and are shown for illustration purposes only. The difference between the data and the best-fit model is shown in the lower panel. |
png pdf |
Figure 4-c:
Background model fits using the chosen ``best-fit" parametrization to the 2018 data in event class 2. The corresponding signal model for each class for $ m_{\mathrm{H}}= $ 90 GeV, multiplied by 10, is also shown. The one- and two-$ \sigma $ bands reflect the uncertainty in the background model normalization associated with the statistical uncertainties of the fits, and are shown for illustration purposes only. The difference between the data and the best-fit model is shown in the lower panel. |
png pdf |
Figure 4-d:
Background model fits using the chosen ``best-fit" parametrization to the 2018 data in the VBF event class. The corresponding signal model for each class for $ m_{\mathrm{H}}= $ 90 GeV, multiplied by 10, is also shown. The one- and two-$ \sigma $ bands reflect the uncertainty in the background model normalization associated with the statistical uncertainties of the fits, and are shown for illustration purposes only. The difference between the data and the best-fit model is shown in the lower panel. |
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Figure 5:
Expected and observed exclusion limits (95% CL, in the asymptotic approximation) on the product of the production cross section and branching fraction into two photons for an additional SM-like Higgs boson, from the analysis of the combined data from 2016, 2017, and 2018. The inner and outer bands indicate the regions containing the distribution of limits located within $ \pm $1 and 2$ \sigma $, respectively, of the expectation under the background-only hypothesis. The limit is shown relative to the expected SM-like value (left). The corresponding theoretical prediction for the product of the cross section and branching fraction into two photons for an additional SM-like Higgs boson is shown as a solid line with a hatched band, indicating its uncertainty [58] (right). |
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Figure 5-a:
Expected and observed exclusion limits (95% CL, in the asymptotic approximation) on the product of the production cross section and branching fraction into two photons for an additional SM-like Higgs boson, from the analysis of the combined data from 2016, 2017, and 2018. The inner and outer bands indicate the regions containing the distribution of limits located within $ \pm $1 and 2$ \sigma $, respectively, of the expectation under the background-only hypothesis. The limit is shown relative to the expected SM-like value. |
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Figure 5-b:
Expected and observed exclusion limits (95% CL, in the asymptotic approximation) on the product of the production cross section and branching fraction into two photons for an additional SM-like Higgs boson, from the analysis of the combined data from 2016, 2017, and 2018. The inner and outer bands indicate the regions containing the distribution of limits located within $ \pm $1 and 2$ \sigma $, respectively, of the expectation under the background-only hypothesis. The corresponding theoretical prediction for the product of the cross section and branching fraction into two photons for an additional SM-like Higgs boson is shown as a solid line with a hatched band, indicating its uncertainty [58]. |
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Figure 6:
Expected and observed exclusion limits (95% CL, in the asymptotic approximation) on the product of the production cross section and branching fraction into two photons for an additional SM-like Higgs boson, for the $ \mathrm{g}\mathrm{g}\mathrm{H} $ plus $ {\mathrm{t}\overline{\mathrm{t}}} \mathrm{H} $ (top left) and VBF plus VH (top right) processes, and assuming 100% production via the VBF (bottom left) and VH (bottom right) processes, from the analysis of the combined data from 2016, 2017, and 2018. The inner and outer bands indicate the regions containing the distribution of limits located within $ \pm $1 and 2$ \sigma $, respectively, of the expectation under the background-only hypothesis. |
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Figure 6-a:
Expected and observed exclusion limits (95% CL, in the asymptotic approximation) on the product of the production cross section and branching fraction into two photons for an additional SM-like Higgs boson, for the $ \mathrm{g}\mathrm{g}\mathrm{H} $ plus $ {\mathrm{t}\overline{\mathrm{t}}} \mathrm{H} $ processes, from the analysis of the combined data from 2016, 2017, and 2018. The inner and outer bands indicate the regions containing the distribution of limits located within $ \pm $1 and 2$ \sigma $, respectively, of the expectation under the background-only hypothesis. |
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Figure 6-b:
Expected and observed exclusion limits (95% CL, in the asymptotic approximation) on the product of the production cross section and branching fraction into two photons for an additional SM-like Higgs boson, for the VBF plus VH processes, from the analysis of the combined data from 2016, 2017, and 2018. The inner and outer bands indicate the regions containing the distribution of limits located within $ \pm $1 and 2$ \sigma $, respectively, of the expectation under the background-only hypothesis. |
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Figure 6-c:
Expected and observed exclusion limits (95% CL, in the asymptotic approximation) on the product of the production cross section and branching fraction into two photons for an additional SM-like Higgs boson, assuming 100% production via the VBF process, from the analysis of the combined data from 2016, 2017, and 2018. The inner and outer bands indicate the regions containing the distribution of limits located within $ \pm $1 and 2$ \sigma $, respectively, of the expectation under the background-only hypothesis. |
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Figure 6-d:
Expected and observed exclusion limits (95% CL, in the asymptotic approximation) on the product of the production cross section and branching fraction into two photons for an additional SM-like Higgs boson, assuming 100% production via the VH process, from the analysis of the combined data from 2016, 2017, and 2018. The inner and outer bands indicate the regions containing the distribution of limits located within $ \pm $1 and 2$ \sigma $, respectively, of the expectation under the background-only hypothesis. |
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Figure 7:
The observed local $ p $-values for an additional SM-like Higgs boson as a function of $ m_{\mathrm{H}} $, from the analysis of the data from 2016, 2017, 2018, and their combination. |
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Figure 8:
Events in all classes of the combined 13 TeV dataset, binned as a function of $ m_{\gamma\gamma} $, together with the result of a fit of the signal-plus-background model, under a mass hypothesis of 95.4 GeV. Each event is weighted by the ratio S/(S+B) for its event class, where S and B are the numbers of expected signal and background events, respectively, in a $ \pm 1\sigma_{\text{eff}} m_{\gamma\gamma} $ window centred on $ m_{\mathrm{H}} $. The one- and two-$ \sigma $ uncertainty bands shown for the background component of the fit include the uncertainty due to the choice of fit function and the uncertainty in the fitted parameters. The distribution of the residual weighted data after subtracting the fitted background component is shown below. |
| Tables | |
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Table 1:
Families and orders of functions chosen as best fit when summed with the DCB plus exponential function, by year and by event class, in the case of background-only fits. The DCB + exponential fractions for these models in the range 85 $ < m_{\gamma\gamma} < $ 95 GeV are also shown. |
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Table 2:
The expected number of SM-like Higgs boson signal events ($ m_{\mathrm{H}}= $ 90 GeV) per event class and the corresponding percentage breakdown per production process, for the 2016, 2017 and 2018 data. The values of $ \sigma_{\text{eff}} $ and $ \sigma_{\text{HM}} $ are also shown, along with the number of background events (``Bkg.'') per GeV estimated from the background-only fit to the data, that includes the number, shown separately, from the Drell--Yan process (``DY Bkg.''), in a $ \sigma_{\text{eff}} $ window centered on $ m_{\mathrm{H}}= $ 90 GeV. |
| Summary |
| A search for an additional, SM-like, low-mass Higgs boson decaying into two photons has been presented. It is based upon data samples corresponding to integrated luminosities of 36.3, 41.5 and 54.4 fb$ ^{-1} $ collected at a center-of-mass energy of 13 TeV in 2016, 2017 and 2018, respectively. The search is performed in a mass range between 70 and 110 GeV. The expected and observed 95% CL upper limits on the product of the production cross section and branching fraction into two photons for an additional SM-like Higgs boson as well as the expected and observed local $ p $-values are presented. The observed upper limit on the product of the production cross section and branching fraction for the combined data set ranges from 73 fb to 15 fb. The statistical combination of the results from the analyses of the three data sets presents an observed excess with respect to the standard model prediction, which is maximal for a mass hypothesis of 95.4 GeV with a local (global) significance of 2.9\,(1.3) standard deviations. This is the first search for new resonances in the diphoton final state in this mass range based on all LHC data collected at a center-of-mass energy of 13 TeV. |
| Additional Figures | |
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Additional Figure 1:
Signal efficiency $ \times $ acceptance for the analysis of the 2016 data set, as a function of mass hypothesis. |
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Additional Figure 2:
Signal efficiency $ \times $ acceptance for the analysis of the 2017 data set, as a function of mass hypothesis. |
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Additional Figure 3:
Signal efficiency $ \times $ acceptance for the analysis of the 2018 data set, as a function of mass hypothesis. |
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Additional Figure 4:
Distributions of the variable $ \ln$($\Sigma p_{T}^{2}$/ GeV$ ^{2}$) for simulated relic Drell--Yan events (red) and simulated signal events corresponding to a SM-like Higgs boson with $ m_{H} = $ 90 GeV produced via the ggH process (black), with both distributions normalized to 1, for the analysis of the 2018 data set. The events are required to have survived the analysis preselection, the pixel detector-based electron veto, and have diphoton BDT classifier values greater than -0.364. This variable, corresponding to the natural logarithm of the sum of the squares of transverse momenta of all tracks associated with the chosen diphoton vertex, is used to suppress the relic Drell--Yan background. For the simulated Drell--Yan events, the peak at $ \sim $8.3 reflects the contributions of the two electron tracks, while the peak at $ \sim $7.6 that of one electron track, the other either being out of the detector acceptance or not reconstructed due to significant bremsstrahlung. The peak at $ \sim $5 corresponds to the case where neither of the electron tracks is reconstructed, similar to that of signal events where the main contributions are from tracks from pileup and the underlying event. |
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Additional Figure 5:
Two-dimensional distribution of $ \ln$($\Sigma p_{T}^{2}$/ GeV$ ^{2}$) versus diphoton transverse momentum ($ p_{T}^{\gamma\gamma} $/GeV) for simulated signal events corresponding to a SM-like Higgs boson with $ m_{H} = $ 90 GeV produced via the ggH process, with the distribution normalized to 1, for the analysis of the 2018 data set. The events are required to have survived the analysis preselection, the pixel detector-based electron veto, and have diphoton BDT classifier values greater than -0.364. The upper limit on $ \ln$($\Sigma p_{T}^{2}$/ GeV$ ^{2}$), $\ln$($\Sigma p_{T}^{2}$/GeV$ ^{2}$) $=$ 0.016 $\times$ $p_{T}^{\gamma\gamma}$/ GeV $+$ 6.0, is shown as the white line. |
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Additional Figure 6:
Two-dimensional distribution of $ \ln$($\Sigma p_{T}^{2}$/ GeV$ ^{2}$) versus diphoton transverse momentum ($ p_{T}^{\gamma\gamma} $/GeV) for simulated relic Drell--Yan events, with the distribution normalized to 1, for the analysis of the 2018 data set. The events are required to have survived the analysis preselection, the pixel detector-based electron veto, and have diphoton BDT classifier values greater than -0.364. The upper limit on $ \ln$($\Sigma p_{T}^{2}$/ GeV$ ^{2}$), $\ln$($\Sigma p_{T}^{2}$/GeV$ ^{2}$) $=$ 0.016 $\times$ $p_{T}^{\gamma\gamma}$/GeV $ + $ 6.0, is shown as the white line. |
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Additional Figure 7:
Expected and observed exclusion limits (95% CL, in the asymptotic approximation) on the product of the production cross section and branching fraction into two photons relative to the value expected for an additional SM-like Higgs boson, from the analysis of the 2016 data set. The inner and outer bands indicate the regions containing the distribution of limits located within $ \pm $1 and 2$ \sigma $, respectively, of the expectation under the background-only hypothesis. |
png pdf |
Additional Figure 8:
Expected and observed exclusion limits (95% CL, in the asymptotic approximation) on the product of the production cross section and branching fraction into two photons, for an additional SM-like Higgs boson, from the analysis of the 2016 data set. The inner and outer bands indicate the regions containing the distribution of limits located within $ \pm $1 and 2$ \sigma $, respectively, of the expectation under the background-only hypothesis. The corresponding theoretical prediction for the product of the cross section and branching fraction into two photons for an additional SM-like Higgs boson is shown as a solid line with a hatched band, indicating its uncertainty. |
png pdf |
Additional Figure 9:
Expected and observed exclusion limits (95% CL, in the asymptotic approximation) on the product of the production cross section and branching fraction into two photons relative to the value expected for an additional SM-like Higgs boson, from the analysis of the 2017 data set. The inner and outer bands indicate the regions containing the distribution of limits located within $ \pm $1 and 2$ \sigma $, respectively, of the expectation under the background-only hypothesis. |
png pdf |
Additional Figure 10:
Expected and observed exclusion limits (95% CL, in the asymptotic approximation) on the product of the production cross section and branching fraction into two photons, for an additional SM-like Higgs boson, from the analysis of the 2017 data set. The inner and outer bands indicate the regions containing the distribution of limits located within $ \pm $1 and 2$ \sigma $, respectively, of the expectation under the background-only hypothesis. The corresponding theoretical prediction for the product of the cross section and branching fraction into two photons for an additional SM-like Higgs boson is shown as a solid line with a hatched band, indicating its uncertainty. |
png pdf |
Additional Figure 11:
Expected and observed exclusion limits (95% CL, in the asymptotic approximation) on the product of the production cross section and branching fraction into two photons relative to the value expected for an additional SM-like Higgs boson, from the analysis of the 2018 data set. The inner and outer bands indicate the regions containing the distribution of limits located within $ \pm $1 and 2$ \sigma $, respectively, of the expectation under the background-only hypothesis. |
png pdf |
Additional Figure 12:
Expected and observed exclusion limits (95% CL, in the asymptotic approximation) on the product of the production cross section and branching fraction into two photons, for an additional SM-like Higgs boson, from the analysis of the 2018 data set. The inner and outer bands indicate the regions containing the distribution of limits located within $ \pm $1 and 2$ \sigma $, respectively, of the expectation under the background-only hypothesis. The corresponding theoretical prediction for the product of the cross section and branching fraction into two photons for an additional SM-like Higgs boson is shown as a solid line with a hatched band, indicating its uncertainty. |
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Additional Figure 13:
Values of the signal strength $ \hat{\mu} $ measured individually for the eleven event classes in the analysis of the combined data from 2016, 2017, and 2018, and the overall combined value, with $ m_H $ fixed to that of the largest local p-value excess. The horizontal bars indicate $ \pm 1\sigma $ uncertainties in the values, and the vertical line and band indicate the value of the combined $ \hat{\mu} $ in the fit to the data and its uncertainty. The $ \chi^2 $ probability of the values for the eleven event classes being compatible with the overall best-fit signal strength is 68%. |
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Additional Figure 14:
Values of the signal strength $ \hat{\mu} $ measured individually for each year, and the overall combined value, with $ m_H $ fixed to that of the largest local p-value excess. The horizontal bars indicate $ \pm 1\sigma $ uncertainties in the values, and the vertical line and band indicate the value of the combined $ \hat{\mu} $ in the fit to the data and its uncertainty. The $ \chi^2 $ probability of the values for the three years being compatible with the overall best-fit signal strength is 6%. |
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Additional Figure 15:
Events in all classes of the combined 13 TeV data set, binned as a function of $ m_{\gamma\gamma} $, together with the result of a fit of the signal-plus-background model, under a mass hypothesis of 95.4 GeV. The one- and two-$ \sigma $ uncertainty bands shown for the background component of the fit include the uncertainty due to the choice of fit function and the uncertainty in the fitted parameters. The distribution of the residual data after subtracting the fitted background component is shown below. |
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