CMS-PAS-FTR-21-007

CMS-PAS-FTR-21-007
Projection of the Higgs boson mass and on-shell width measurements in H $\to$ ZZ* $\to 4\ell$ decay channel at the HL-LHC
CMS Collaboration
March 2022

Abstract: The CMS High-Luminosity LHC projection of the Higgs boson mass and on-shell width measurement in the H $\to$ ZZ* $\to 4\ell$ ($\ell=$ e, $\mu$) decay channel is presented, processing a foreseen integrated luminosity of 3000 fb$^{-1}$. Several improvements, including a new approach to build the final likelihood, are implemented. The impact of the detector Phase-2 upgrades are studied considering different alternative systematic uncertanties scenarios.
Links: CDS record (PDF) ; CADI line (restricted) ;

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Distribution of the four lepton invariant mass: inclusive (top), 4$\mu $ in the middle left, 4e middle right, 2e2$\mu $ bottom left and 2$\mu $2e bottom right.
png pdf	Figure 1-a: Distribution of the four lepton invariant mass: inclusive (top), 4$\mu $ in the middle left, 4e middle right, 2e2$\mu $ bottom left and 2$\mu $2e bottom right.
png pdf	Figure 1-b: Distribution of the four lepton invariant mass: inclusive (top), 4$\mu $ in the middle left, 4e middle right, 2e2$\mu $ bottom left and 2$\mu $2e bottom right.
png pdf	Figure 1-c: Distribution of the four lepton invariant mass: inclusive (top), 4$\mu $ in the middle left, 4e middle right, 2e2$\mu $ bottom left and 2$\mu $2e bottom right.
png pdf	Figure 1-d: Distribution of the four lepton invariant mass: inclusive (top), 4$\mu $ in the middle left, 4e middle right, 2e2$\mu $ bottom left and 2$\mu $2e bottom right.
png pdf	Figure 1-e: Distribution of the four lepton invariant mass: inclusive (top), 4$\mu $ in the middle left, 4e middle right, 2e2$\mu $ bottom left and 2$\mu $2e bottom right.
png pdf	Figure 2: Fits of the four lepton invariant mass distribution (4$\mu $ in the top left, 4e top right, 2e2$\mu $ bottom left and 2$\mu $2e bottom right) showing the impact of the different lepton momentum improvements: blue line no improvements, red line when VXBS is included and green line when also on-shell Z constraint is applied. The function used is a DSCB.
png pdf	Figure 2-a: Fits of the four lepton invariant mass distribution (4$\mu $ in the top left, 4e top right, 2e2$\mu $ bottom left and 2$\mu $2e bottom right) showing the impact of the different lepton momentum improvements: blue line no improvements, red line when VXBS is included and green line when also on-shell Z constraint is applied. The function used is a DSCB.
png pdf	Figure 2-b: Fits of the four lepton invariant mass distribution (4$\mu $ in the top left, 4e top right, 2e2$\mu $ bottom left and 2$\mu $2e bottom right) showing the impact of the different lepton momentum improvements: blue line no improvements, red line when VXBS is included and green line when also on-shell Z constraint is applied. The function used is a DSCB.
png pdf	Figure 2-c: Fits of the four lepton invariant mass distribution (4$\mu $ in the top left, 4e top right, 2e2$\mu $ bottom left and 2$\mu $2e bottom right) showing the impact of the different lepton momentum improvements: blue line no improvements, red line when VXBS is included and green line when also on-shell Z constraint is applied. The function used is a DSCB.
png pdf	Figure 2-d: Fits of the four lepton invariant mass distribution (4$\mu $ in the top left, 4e top right, 2e2$\mu $ bottom left and 2$\mu $2e bottom right) showing the impact of the different lepton momentum improvements: blue line no improvements, red line when VXBS is included and green line when also on-shell Z constraint is applied. The function used is a DSCB.
png pdf	Figure 3: Fits of the 4$\mu $ invariant mass distribution, using Delphes samples (red line) and CMS Run 2 one (blue line). The production mode considered is gg $\to$ HH.
png pdf	Figure 4: 1D likelihood scan comparing the impact of the systematic uncertainties (on the left) and the contribution of each final state (Stat only - on the right).
png pdf	Figure 4-a: 1D likelihood scan comparing the impact of the systematic uncertainties (on the left) and the contribution of each final state (Stat only - on the right).
png pdf	Figure 4-b: 1D likelihood scan comparing the impact of the systematic uncertainties (on the left) and the contribution of each final state (Stat only - on the right).
png pdf	Figure 5: 2D likelihood scan for the Higgs boson width.

Tables
png pdf	Table 1: Expected yields at 3000 fb$^{-1}$ for signal and background, in the inclusive decay channel and split for final state.
png pdf	Table 2: Impact of the dominant systematic uncertaintes for the different scenarios considered in the projection. As reference, YR column reports latest projection assumptions.
png pdf	Table 3: Expected Higgs boson mass measurement uncertainty, given in MeV, in the inclusive final state.
png pdf	Table 4: Expected Higgs boson mass measurement uncertainty, given in MeV, for the four different final states.
png pdf	Table 5: Higgs boson width upper limit at 95% C.L.
png pdf	Table 6: Expected Higgs boson mass measurement uncertainty, given in MeV, in the two different scenarios: Optimistic and Pessimistic.
png pdf	Table 7: Expected Higgs boson width upper limit, at 95% C.L. comparing different scenarios.

Summary

Projection at the HL-LHC for the measurement of the Higgs boson mass and width, considering the on-shell production and the decay into four leptons has been presented. The scenario of 3000 fb$^{-1}$ at 14 TeV collected and analyzed by the CMS detector has been considered. The analysis workflow adopted follows the one described in Ref. [6] and [7] with several improvements, including a new approach implemented to build the final likelihood. The latest public observed results for Higgs boson mass and on-shell width measurements in the four leptons final state were extracted from the analysis of 36 fb$^{-1}$ data collected during LHC Run 2, in 2016 as follows [6]: $m_{\mathrm{H}} = $ 125.26 $\pm$ 0.20 (stat) $\pm$ 0.08 (syst) GeV and $\Gamma_{\mathrm{H}} < $ 0.41(1.10) GeV at 68(95)% confidence level. The projected expected result, at the HL-LHC, for mass measurement, is $m_{\mathrm{H}} = $ 125.38 $\pm$ 0.03 [0.022(stat) $\pm$ 0.020 (syst)] GeV and for width is $\Gamma_{\mathrm{H}} < $ 0.09 (0.18) GeV at 68(95)% confidence level. Further mass measurement improvements are foreseeable if detector upgrades are taken into account. Increased acceptance for muons and electrons and reduced systematic uncertainties (Optimistic scenario), reachable with additional statistics at the HL-LHC that will allow a better lepton calibration, lead to a mass error of 20 MeV including both statistical and systematic uncertainties.

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