CMS-PAS-HIG-24-007

CMS-PAS-HIG-24-007
A measurement of the Higgs boson mass in the diphoton decay channel with the CMS detector
CMS Collaboration
2026-03-19

Abstract: A measurement of the Higgs boson mass in the diphoton decay channel is performed using proton-proton collision data at a centre-of-mass energy of 13 TeV. The dataset recorded with the CMS detector between 2016 and 2018 is used, corresponding to an integrated luminosity of 138 $ \textrm{fb}^{-1} $. A refined detector calibration and new analysis techniques have been used to improve the precision of these results over earlier measurements. The Higgs boson mass is measured to be $ m_{\textrm{H}} = $ 125.14 $ \pm $ 0.10 $ \textrm{(stat)} \pm 0.11 \textrm{(syst)} \textrm{GeV} $. In addition, a combination with the Run 1 mass measurement at 7 and 8 $ \textrm{TeV} $ in the diphoton final state is performed resulting in $ m_{\textrm{H}} = $ 125.07 $ \pm $ 0.09 $ \textrm{(stat)} \pm 0.10 \textrm{(syst)} \textrm{GeV} $.
Links: CDS record (PDF) ; CADI line (restricted) ;

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Comparison of the dielectron invariant mass distribution in data and simulation for $ \mathrm{Z}\rightarrow\mathrm{e}\mathrm{e} $ events after applying only the electron energy corrections. Both electrons are required to have $ E_\mathrm{T} > $ 50 GeV and to be reconstructed in the ECAL barrel region. The error bands account for the statistical uncertainty and the systematic uncertainty associated with the energy scale corrections.
png pdf	Figure 2: Photon energy scale corrections as a function of $ \|\eta_\gamma\| $ in two $ E_{\mathrm{T}} $ bins, using $ \mathrm{Z}\rightarrow\mu\mu\gamma $ events, after applying the electron energy scale and uniformity corrections. The shaded bands indicate the statistical uncertainties from the simulation, while the error bars show the total statistical uncertainties.
png pdf	Figure 3: Comparison of the three-body invariant mass distribution in data and simulation for $ \mathrm{Z}\rightarrow\mu\mu\gamma $ events in the ECAL barrel region ($ \|\eta_\gamma\| < $ 1.44) with $ E_{\mathrm{T},\gamma} > $ 50 GeV. The left panel shows the distribution after the first two calibration stages, without the final photon energy scale correction derived from FSR photons. The right panel shows the same distribution after applying the final photon energy scale corrections.
png pdf	Figure 3-a: Comparison of the three-body invariant mass distribution in data and simulation for $ \mathrm{Z}\rightarrow\mu\mu\gamma $ events in the ECAL barrel region ($ \|\eta_\gamma\| < $ 1.44) with $ E_{\mathrm{T},\gamma} > $ 50 GeV. The left panel shows the distribution after the first two calibration stages, without the final photon energy scale correction derived from FSR photons. The right panel shows the same distribution after applying the final photon energy scale corrections.
png pdf	Figure 3-b: Comparison of the three-body invariant mass distribution in data and simulation for $ \mathrm{Z}\rightarrow\mu\mu\gamma $ events in the ECAL barrel region ($ \|\eta_\gamma\| < $ 1.44) with $ E_{\mathrm{T},\gamma} > $ 50 GeV. The left panel shows the distribution after the first two calibration stages, without the final photon energy scale correction derived from FSR photons. The right panel shows the same distribution after applying the final photon energy scale corrections.
png pdf	Figure 4: Signal model for the analysis category with the best mass resolution (left), and for all categories combined after scaling by their corresponding $ \textrm{S/(S+B)} $ ratios (right), for a simulated $ \mathrm{H}\rightarrow\gamma\gamma $ signal sample with $ m_{\textrm{H}} = $ 125 GeV. All Higgs boson production modes are summed.
png pdf	Figure 4-a: Signal model for the analysis category with the best mass resolution (left), and for all categories combined after scaling by their corresponding $ \textrm{S/(S+B)} $ ratios (right), for a simulated $ \mathrm{H}\rightarrow\gamma\gamma $ signal sample with $ m_{\textrm{H}} = $ 125 GeV. All Higgs boson production modes are summed.
png pdf	Figure 4-b: Signal model for the analysis category with the best mass resolution (left), and for all categories combined after scaling by their corresponding $ \textrm{S/(S+B)} $ ratios (right), for a simulated $ \mathrm{H}\rightarrow\gamma\gamma $ signal sample with $ m_{\textrm{H}} = $ 125 GeV. All Higgs boson production modes are summed.
png pdf	Figure 5: Uncertainties in the energy scale as a function of $ E_\mathrm{T} $ in the barrel region, derived from $ \mathrm{Z}\rightarrow\mu\mu\gamma $ events. The shaded bands indicate the statistical and total uncertainties, while the dashed lines show the individual contributions from the electromagnetic shower modelling, muon momentum scale and non-linearity.
png pdf	Figure 6: Data and combined signal and background model fit for all analysis categories, unweighted (left) and 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 is subtracted.
png pdf	Figure 6-a: Data and combined signal and background model fit for all analysis categories, unweighted (left) and 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 is subtracted.
png pdf	Figure 6-b: Data and combined signal and background model fit for all analysis categories, unweighted (left) and 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 is subtracted.
png pdf	Figure 7: Likelihood scans of the Higgs boson mass measured in the $ \mathrm{H}\rightarrow\gamma\gamma $ decay channel for the Run 1 and Run 2 datasets, and their combination. Solid lines show the full likelihood scan including systematic uncertainties, while dashed lines correspond to the statistical-only case.
png pdf	Figure 8: Summary of the ATLAS and CMS Higgs boson mass measurements using the diphoton and the four-lepton final states, combing Run 1 and Run 2 results. The black point represents the best fit value of each measurement. The yellow and grey bands show the statistical and systematic uncertainties in each measurement, respectively. The horizontal black bars show the total uncertainties. The value of each measurement is given, along with the total uncertainties, splitting statistical only and systematic only uncertainties in parentheses.

Tables
png pdf	Table 1: Observed impact of the different sources of systematic uncertainty in the measurement of $ m_{\textrm{H}} $

Summary

A new measurement of the Higgs boson mass has been conducted in the diphoton decay channel, utilising the complete dataset collected by CMS between 2016 and 2018 during Run 2 at $ \sqrt{s} = $ 13 TeV at the CERN LHC. New analysis techniques, enabled by the increased integrated luminosity, were used to improve the measurement precision, refine the detector calibration, and derive corrections accounting for differences between photons and electrons. The main improvements with respect to the previous analysis [8] include the derivation of granular $ E_\mathrm{T} $-dependent energy smearing corrections, a new simulation-based method to correct for differences between the photon and electron energy scales due to radiation damage in the ECAL crystals, and a calibration procedure using $ \mathrm{Z}\rightarrow\mu\mu\gamma $ events to correct residual energy scale differences between electrons and photons. In addition, a signal-to-background classifier based on gradient boosting was employed, with backgrounds containing at least one jet misidentified as a photon estimated using a data-driven technique. To further enhance the measurement sensitivity, multiple analysis categories were defined according to the classifier output, using a figure of merit that accounts for both the signal-to-background ratio and the relative diphoton mass resolution. The Higgs boson mass is measured to be $ m_{\textrm{H}} = $ 125.14 $ \pm $ 0.10 (stat) $ \pm $ 0.11 (syst) GeV. When combined with the corresponding measurement from CMS Run 1 data, the mass is determined to be $ m_{\textrm{H}} = $ 125.07 $ \pm $ 0.09 (stat) $ \pm $ 0.10 (syst) GeV. \newpage

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