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| CMS-HIG-19-013 ; CERN-EP-2020-028 | ||
| Measurements of ${\mathrm{t\bar{t}}\mathrm{H}} $ production and the CP structure of the Yukawa interaction between the Higgs boson and top quark in the diphoton decay channel | ||
| CMS Collaboration | ||
| 25 March 2020 | ||
| Phys. Rev. Lett. 125 (2020) 061801 | ||
| Abstract: The first observation of the ${\mathrm{t\bar{t}}\mathrm{H}}$ process in a single Higgs boson decay channel with the full reconstruction of the final state (${\mathrm{H} \to \gamma\gamma} $) is presented, with a significance of 6.6 standard deviations ($\sigma$). The CP structure of Higgs boson couplings to fermions is measured, resulting in an exclusion of the pure CP-odd structure of the top Yukawa coupling at 3.2$\sigma$. The measurements are based on a sample of proton-proton collisions at a center-of-mass energy $\sqrt{s}=$ 13 TeV collected by the CMS detector at the LHC, corresponding to an integrated luminosity of 137 fb$^{-1}$. The cross section times branching fraction of the ${\mathrm{t\bar{t}}\mathrm{H}}$ process is measured to be ${\sigma_{{\mathrm{t\bar{t}}\mathrm{H}} } \mathcal{B}_{\gamma\gamma}}= $ 1.56$^{+0.34}_{-0.32}$ fb, which is compatible with the standard model prediction of 1.13$^{+0.08}_{-0.11}$ fb. The fractional contribution of the CP-odd component is measured to be ${f_{\mathrm{CP}}^{{\mathrm{H}\mathrm{t}\mathrm{t}} }} =$ 0.00 $\pm$ 0.33. | ||
| Links: e-print arXiv:2003.10866 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ; | ||
| Figures & Tables | Summary | Additional Figures | References | CMS Publications |
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| Figures | |
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Figure 1:
Distributions of BDT-bkg output used for event categorization, for the hadronic (left) and the leptonic (right) channels. Category boundaries for the signal strength (CP) measurements are shown with thinly (thickly) dashed lines. Events shown are taken from the ${m_{\gamma \gamma}}$ sidebands, satisfying either 100 $ < {m_{\gamma \gamma}} < $ 120 GeV or 130 $ < {m_{\gamma \gamma}} < $ 180 GeV. Events in the grey shaded region are not considered in the analysis. Statistical (statistical $\oplus $ systematic) background uncertainties are represented by the black (red) shaded bands. |
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Figure 1-a:
Distribution of the BDT-bkg output used for event categorization, for the hadronic channel. Category boundaries for the signal strength (CP) measurements are shown with thinly (thickly) dashed lines. Events shown are taken from the ${m_{\gamma \gamma}}$ sidebands, satisfying either 100 $ < {m_{\gamma \gamma}} < $ 120 GeV or 130 $ < {m_{\gamma \gamma}} < $ 180 GeV. Events in the grey shaded region are not considered in the analysis. Statistical (statistical $\oplus $ systematic) background uncertainties are represented by the black (red) shaded bands. |
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Figure 1-b:
Distribution of the BDT-bkg output used for event categorization, for the leptonic channel. Category boundaries for the signal strength (CP) measurements are shown with thinly (thickly) dashed lines. Events shown are taken from the ${m_{\gamma \gamma}}$ sidebands, satisfying either 100 $ < {m_{\gamma \gamma}} < $ 120 GeV or 130 $ < {m_{\gamma \gamma}} < $ 180 GeV. Events in the grey shaded region are not considered in the analysis. Statistical (statistical $\oplus $ systematic) background uncertainties are represented by the black (red) shaded bands. |
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Figure 2:
Invariant mass distribution for the selected events (black points) weighted by S/(S + B), where S (B) is the numbers of expected signal (background) events in a $ \pm $1$\sigma _{\mathrm {eff}}$ mass window centered on ${m_{\mathrm{H}}}$. The $\sigma _{\mathrm {eff}}$ is defined as the smallest interval containing 68.3% of the ${m_{\gamma \gamma}}$ distribution, and ranges from 1.2 to 1.6% for different categories. We show curves for fitted signal $\oplus $ background (solid red) and for background only (dashed red), with bands covering the $ \pm $1$ \sigma $ and $ \pm$2$ \sigma $ uncertainties in the fitted background. The inner panel shows the likelihood scan for $\mu _{{{\mathrm{t} {}\mathrm{\bar{t}}} \mathrm{H}}}$ with ${m_{\mathrm{H}}}$ profiled. |
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Figure 3:
The distribution of events weighted by S/(S + B), as in Fig. 2, in three bins of the $\mathcal {D}_{0-}$ discriminant. In this display, leptonic/hadronic channels and BDT-bkg categories are combined in the mass range 115 $ < {m_{\gamma \gamma}} < $ 135 GeV and the background contribution, as determined in the fit to data, is subtracted. The inner panel shows the likelihood scan for $ {| {f_{\mathrm {CP}}^{{\mathrm{H} \mathrm{t} \mathrm{t}}}} |}$. |
| Tables | |
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Table 1:
The expected number of H events in the hadronic and leptonic channels per category and the fractional contribution per H production mode. |
| Summary |
| To conclude, we presented the first single-channel observation of the ${\mathrm{t\bar{t}}\mathrm{H}}$ process and the first measurement of the CP structure of the Htt coupling using the ${\mathrm{H \to \gamma\gamma}}$ channel. The cross section of the ${\mathrm{t\bar{t}}\mathrm{H}}$ process is measured to be ${\sigma_{{\mathrm{t\bar{t}}\mathrm{H}} } \mathcal{B}_{\gamma\gamma}} = $ 1.56$^{+0.34}_{-0.32}$ fb, corresponding to 1.38$^{+0.36}_{-0.29}$ times the SM prediction, with a significance of 6.6$\sigma$. The data disfavor the pure CP-odd model of the ${\mathrm{Ht\bar{t}}}$ coupling at 3.2$\sigma$, and a possible fractional CP-odd contribution is constrained to be $f^{\text{Htt}}_{\text{CP}}=$ 0.00 $\pm$ 0.33 at 68% CL. |
| Additional Figures | |
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Additional Figure 1:
Distributions of the output of the BDTs evaluated with events from the ttZ control region, for the hadronic channel. The shaded bands show the statistical and systematic uncertainties. |
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Additional Figure 2:
Distributions of the output of the BDTs evaluated with events from the ttZ control region, for the leptonic channel. The shaded bands show the statistical and systematic uncertainties. |
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Additional Figure 3:
Data and signal-plus-background model fits in ttH Hadronic Tag 1 category are shown. The one (green) and two (yellow) standard deviation bands include the uncertainties in the background component of the fit. The lower panel shows the residuals after the background subtraction. |
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Additional Figure 4:
Data and signal-plus-background model fits in ttH Hadronic Tag 2 category are shown. The one (green) and two (yellow) standard deviation bands include the uncertainties in the background component of the fit. The lower panel shows the residuals after the background subtraction. |
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Additional Figure 5:
Data and signal-plus-background model fits in ttH Hadronic Tag 3 category are shown. The one (green) and two (yellow) standard deviation bands include the uncertainties in the background component of the fit. The lower panel shows the residuals after the background subtraction. |
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Additional Figure 6:
Data and signal-plus-background model fits in ttH Hadronic Tag 4 category are shown. The one (green) and two (yellow) standard deviation bands include the uncertainties in the background component of the fit. The lower panel shows the residuals after the background subtraction. |
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Additional Figure 7:
Data and signal-plus-background model fits in ttH Leptonic Tag 1 category are shown. The one (green) and two (yellow) standard deviation bands include the uncertainties in the background component of the fit. The lower panel shows the residuals after the background subtraction. |
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Additional Figure 8:
Data and signal-plus-background model fits in ttH Leptonic Tag 2 category are shown. The one (green) and two (yellow) standard deviation bands include the uncertainties in the background component of the fit. The lower panel shows the residuals after the background subtraction. |
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Additional Figure 9:
Data and signal-plus-background model fits in ttH Leptonic Tag 3 category are shown. The one (green) and two (yellow) standard deviation bands include the uncertainties in the background component of the fit. The lower panel shows the residuals after the background subtraction. |
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Additional Figure 10:
Data and signal-plus-background model fits in ttH Leptonic Tag 3 category are shown. The one (green) and two (yellow) standard deviation bands include the uncertainties in the background component of the fit. The lower panel shows the residuals after the background subtraction. |
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Additional Figure 11:
Data and signal-plus-background model fits for all categories summed. The one (green) and two (yellow) standard deviation bands include the uncertainties in the background component of the fit. The lower panel shows the residuals after the background subtraction. |
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Additional Figure 12:
Data and signal-plus-background model fits for all categories summed weighted by their sensitivity (right). The one (green) and two (yellow) standard deviation bands include the uncertainties in the background component of the fit. The lower panel shows the residuals after the background subtraction. |
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Additional Figure 13:
observed likelihood scan, produced with a simultaneous fit to the $m_{\gamma \gamma}$ distributions of all categories and with $m_H$ profiled. |
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Additional Figure 14:
Data distribution in hadronic channel. The total signal and background models are shown in red ($f_{CP}=$ 0) and blue ($f_{CP}=$ 1). |
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Additional Figure 15:
Data distribution in hadronic channel. The total signal and background models are shown in red ($f_{CP}=$ 0) and blue ($f_{CP}=$ 1). |
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Additional Figure 16:
Data distribution in hadronic channel. The total signal and background models are shown in red ($f_{CP}=$ 0) and blue ($f_{CP}=$ 1). |
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Additional Figure 17:
Data distribution in hadronic channel. The total signal and background models are shown in red ($f_{CP}=$ 0) and blue ($f_{CP}=$ 1). |
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Additional Figure 18:
Data distribution in hadronic channel. The total signal and background models are shown in red ($f_{CP}=$ 0) and blue ($f_{CP}=$ 1). |
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Additional Figure 19:
Data distribution in hadronic channel. The total signal and background models are shown in red ($f_{CP}=$ 0) and blue ($f_{CP}=$ 1). |
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Additional Figure 20:
Data distribution in leptonic channel. The total signal and background models are shown in red ($f_{CP}=$ 0) and blue ($f_{CP}=$ 1). |
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Additional Figure 21:
Data distribution in leptonic channel. The total signal and background models are shown in red ($f_{CP}=$ 0) and blue ($f_{CP}=$ 1). |
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Additional Figure 22:
Data distribution in leptonic channel. The total signal and background models are shown in red ($f_{CP}=$ 0) and blue ($f_{CP}=$ 1). |
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Additional Figure 23:
Data distribution in leptonic channel. The total signal and background models are shown in red ($f_{CP}=$ 0) and blue ($f_{CP}=$ 1). |
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Additional Figure 24:
Data distribution in leptonic channel. The total signal and background models are shown in red ($f_{CP}=$ 0) and blue ($f_{CP}=$ 1). |
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Additional Figure 25:
Data distribution in leptonic channel. The total signal and background models are shown in red ($f_{CP}=$ 0) and blue ($f_{CP}=$ 1). |
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Additional Figure 26:
Expected and observed likelihood scans of the $f_{CP}$ parameter. |
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