CMS-PAS-HIG-19-004 | ||

A measurement of the Higgs boson mass in the diphoton decay channel | ||

CMS Collaboration | ||

September 2019 | ||

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Abstract:
A measurement of the mass of the Higgs boson in the diphoton decay channel is presented. This analysis is based on 35.9 fb$^{-1}$ of proton-proton collision data collected in 2016 with the CMS detector at a center-of-mass energy of 13 TeV. The Higgs boson mass is measured to be $m_\text{H}$ = 125.78 $\pm$ 0.26 GeV. This is combined with a measurement of $m_\text{H}$ already performed in the $\mathrm{H} \rightarrow \mathrm{ZZ}^{*} \rightarrow 4\ell$ decay channel using the same dataset, giving $m_\text{H}$ = 125.46 $\pm$ 0.17 GeV. This result, when combined with an earlier measurement of the Higgs boson mass using data collected in 2011 and 2012 with the CMS detector, gives a value for the Higgs boson mass of $m_\text{H}$ = 125.35 $\pm$ 0.15 GeV. In this note we summarize the strategy of this measurement in the $\mathrm{H}\rightarrow \gamma \gamma$ final state emphasizing the methods employed to mitigate and to quantify the main sources of systematic uncertainty. The combination strategy is also described.
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Links:
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These preliminary results are superseded in this paper, PLB 805 (2020) 135425.The superseded preliminary plots can be found here. |

Figures | |

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Figure 1:
Energy scale corrections applied to data as function of the ${p_{\mathrm{T}}}$ of the photon. The systematic uncertainty associated to this correction is approximately the maximum deviation observed in the ${p_{\mathrm{T}}}$ range between 45 and 65 GeV for electrons in the ECAL barrel region. |

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Figure 2:
Comparison of the distributions of the invariant mass of the dielectrons in data and simulation in ${\mathrm{Z} \rightarrow \mathrm{e^{+}e^{-}}}$ events after application of energy corrections in two representative categories. Left: Both electrons are in the ECAL barrel and satisfy $ {R_\mathrm {9}} > $ 0.94. Right: The leading electron has a transverse momentum between 55 and 65 GeV, without a requirement on the second electron. The systematic uncertainty in the error band in the plots include only the uncertainties on the derived energy scale corrections. |

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Figure 2-a:
Comparison of the distributions of the invariant mass of the dielectrons in data and simulation in ${\mathrm{Z} \rightarrow \mathrm{e^{+}e^{-}}}$ events after application of energy corrections in the category with both electrons in the ECAL barrel and satisfy $ {R_\mathrm {9}} > $ 0.94. The systematic uncertainty in the error band includes only the uncertainties on the derived energy scale corrections. |

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Figure 2-b:
Comparison of the distributions of the invariant mass of the dielectrons in data and simulation in ${\mathrm{Z} \rightarrow \mathrm{e^{+}e^{-}}}$ events after application of energy corrections in the category for which the leading electron has a transverse momentum between 55 and 65 GeV, without a requirement on the second electron. The systematic uncertainty in the error band includes only the uncertainties on the derived energy scale corrections. |

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Figure 3:
The signal shape models for the highest resolution analysis category (left), and the sum of all categories combined together after scaling each of them by the corresponding S/(S+B) ratio (right) for a simulated ${\mathrm{H} \rightarrow \gamma \gamma}$ signal sample with ${m_\mathrm{H}} =$ 125 GeV. The open squares represent weighted simulation events and the blue line the corresponding model. Also shown is the $\sigma _\text {eff}$ value (half the width of the narrowest interval containing 68.3% of the invariant mass distribution) and the full width at half of the maximum (FWHM). |

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Figure 3-a:
The signal shape models for the highest resolution analysis category (left), and the sum of all categories combined together after scaling each of them by the corresponding S/(S+B) ratio (right) for a simulated ${\mathrm{H} \rightarrow \gamma \gamma}$ signal sample with ${m_\mathrm{H}} =$ 125 GeV. The open squares represent weighted simulation events and the blue line the corresponding model. Also shown is the $\sigma _\text {eff}$ value (half the width of the narrowest interval containing 68.3% of the invariant mass distribution) and the full width at half of the maximum (FWHM). |

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Figure 3-b:
The signal shape models for the highest resolution analysis category (left), and the sum of all categories combined together after scaling each of them by the corresponding S/(S+B) ratio (right) for a simulated ${\mathrm{H} \rightarrow \gamma \gamma}$ signal sample with ${m_\mathrm{H}} =$ 125 GeV. The open squares represent weighted simulation events and the blue line the corresponding model. Also shown is the $\sigma _\text {eff}$ value (half the width of the narrowest interval containing 68.3% of the invariant mass distribution) and the full width at half of the maximum (FWHM). |

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Figure 4:
The systematic uncertainty due to the difference between the electron and photon energy scale due to radiation damage induced non-uniformity of light collection in ECAL crystals in different supercluster $ {| \eta _{SC} |}$ and ${R_\mathrm {9}}$ categories. The method used to evaluate this is described in Section 8.2. |

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Figure 5:
Data and signal-plus-background model fits for all categories summed (left) and where the categories are 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 in each plot shows the residuals after the background subtraction. |

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Figure 5-a:
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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Figure 5-b:
Data and signal-plus-background model fits where the categories are summed weighted by their sensitivity. 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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Figure 6:
The expected number of signal events per category and the percentage breakdown per production mode. The $\sigma _\text {eff}$ value (half the width of the narrowest interval containing 68.3% of the invariant mass distribution) is also shown as an estimate of the $m_{\gamma \gamma}$ resolution in that category and compared directly to the $\sigma _\text {HM}$. The ratio of the number of signal events (S) to the number of signal plus background events (S+B) is shown on the right hand side. |

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Figure 7:
The likelihood scan of the measured Higgs boson mass in the ${\mathrm{H} \rightarrow \gamma \gamma}$ and ${\mathrm{H} \rightarrow \mathrm{ZZ}^{*} \rightarrow 4\ell}$ decay channels individually and for the combination with the 2016 data set. The solid lines are for the full likelihood scan including all systematic uncertainties, while the dashed lines denote the same with the statistical uncertainty only. The additional 5% uncertainty due to treating the electron and photon energy scales as uncorrelated between the two decay channels for the combination is not included in the combined likelihood scan. |

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Figure 8:
The likelihood scan of the combined Higgs boson mass in the ${\mathrm{H} \rightarrow \gamma \gamma}$ and ${\mathrm{H} \rightarrow \mathrm{ZZ}^{*} \rightarrow 4\ell}$ decay channels with the Run 1 and 2016 data sets individually and the same combining the two data sets. The solid lines are for the full likelihood scan including all systematic uncertainties, while the dashed lines denote the same with the statistical uncertainty only. The additional 5% uncertainty due to treating the electron and photon energy scales as uncorrelated between the two decay channels for the combination with the 2016 data set and the Run 1 + 2016 data sets is not included in the corresponding combined likelihood scans. |

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Figure 9:
A summary of the measured Higgs boson mass individually in the ${\mathrm{H} \rightarrow \gamma \gamma}$ and ${\mathrm{H} \rightarrow \mathrm{ZZ}^{*} \rightarrow 4\ell}$ decay channels, and for the combination of the two is presented here. The statistical (wider, yellow-shaded bands), and total (black error bars) uncertainties are indicated. The (red) vertical line and corresponding (gray) shaded column indicate the central value and the total uncertainty of the Run 1 + 2016 combined measurement, respectively. |

Tables | |

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Table 1:
The observed impact of the different sources of systematic uncertainty on the measurement of ${m_\mathrm{H}}$. |

Summary |

In this note we have described a measurement of the Higgs boson mass in the diphoton decay channel. This analysis has taken advantage of the higher integrated luminosity data collected in 2016 at $\sqrt{s} = $ 13 TeV at the CERN LHC. New analysis techniques have been introduced to improve the precision of the measurement and we have used an improved detector calibration. The techniques that are new with respect to the previous analysis in the diphoton decay channel [7] are the introduction of residual energy corrections in much finer bins of the shower-shape variable, ${R_\mathrm{9}} $, and $\eta$, and the development of a procedure to derive ${p_{\mathrm{T}}}$ dependent corrections to the photon energy scale. We have also employed a new method to estimate the systematic uncertainty due to changes in the transparency of the ECAL crystals with radiation damage. The measured value of the Higgs boson mass in the diphoton decay channel is found to be ${m_\mathrm{H}} =$ 125.78 $\pm$ 0.26 GeV. This measurement has been combined with a recent measurement by CMS of the same quantity in the $\mathrm{H} \rightarrow \mathrm{ZZ}^{*} \rightarrow 4\ell$ decay channel [5] to obtain a value of ${m_\mathrm{H}} =$ 125.46 $\pm$ 0.17 GeV. Furthermore, when the Run 2 result with the 2016 data set is combined with the same measurement performed in Run 1 at 7 and 8 TeV the value of the Higgs boson mass is found to be ${m_\mathrm{H}} =$ 125.35 $\pm$ 0.15 GeV. |

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Compact Muon Solenoid LHC, CERN |