CMS-PAS-SMP-24-015

CMS-PAS-SMP-24-015
Measurement of WWZ and ZH cross sections at $\sqrt{s}=$ 13 and 13.6 TeV in the four-lepton channel with the CMS detector
CMS Collaboration
3 March 2025

Abstract: A measurement is presented of the cross section in proton-proton collisions for the production of two W bosons and one Z boson. It is based on a data recorded by the CMS experiment at the CERN LHC at center-of-mass energies $\sqrt{s}$ =13 and 13.6 TeV, and corresponding to an integrated luminosity of 200 fb $^{-1}$ . Events with four leptons (electrons or muons) in the final state are selected. Both non-resonant WWZ production and ZH production, with the Higgs boson decaying to two W bosons, are considered. For the first time, the two processes are measured simultaneously. Signal strengths relative to the standard model (SM) predictions of 0.75 $^{+0.34}_{-0.29}$ and 1.74 $^{+0.71}_{-0.60}$ are measured for $\sqrt{s}$ =13 and 13.6 TeV respectively. The observed (expected) significance for the tri-boson signal is found to be 3.83 (2.49) standard deviations for $\sqrt{s}$ =13 TeV, thus providing the first evidence at this center-of-mass energy. Taking all data together, the signal strength relative to the SM prediction is measured to be 1.03 $^{+0.31}_{-0.28}$ , with an observed (expected) significance of 4.53 (5.04) standard deviations.
Links: CDS record (PDF) ; CADI line (restricted) ;

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Example Feynman diagrams for non-resonant $\mathrm{W}\mathrm{W}\mathrm{Z}$ (left) and ZH (with $\mathrm{H} \to \mathrm{W}\mathrm{W}$ ) production (right).
png pdf	Figure 2: Comparison of the observed number of events to the predicted number of events (corresponding to the SM expectation) for each of the bins included in the fit for Run 2 (top) and Run 3 (bottom).
png pdf	Figure 2-a: Comparison of the observed number of events to the predicted number of events (corresponding to the SM expectation) for each of the bins included in the fit for Run 2 (top) and Run 3 (bottom).
png pdf	Figure 2-b: Comparison of the observed number of events to the predicted number of events (corresponding to the SM expectation) for each of the bins included in the fit for Run 2 (top) and Run 3 (bottom).
png pdf	Figure 3: One-dimensional likelihood scan as a function of the inclusive $\mathrm{W}\mathrm{W}\mathrm{Z}$ and ZH signal strength parameter ( $\mu_{\mathrm{W}\mathrm{W}\mathrm{Z}+\mathrm{Z}\mathrm{H}}$ ) for Run 2 and Run 3 (left), and two-dimensional likelihood scan as a function of the $\mathrm{W}\mathrm{W}\mathrm{Z}$ and ZH signal strength parameters for Run 2 and Run 3 (right). For the two-dimensional scan the one and two standard deviation ( $\sigma$ ) contours are indicated by the dotted and solid lines, respectively. In the signal strengths reported here, the uncertainty of the predicted cross section is not included.
png pdf	Figure 3-a: One-dimensional likelihood scan as a function of the inclusive $\mathrm{W}\mathrm{W}\mathrm{Z}$ and ZH signal strength parameter ( $\mu_{\mathrm{W}\mathrm{W}\mathrm{Z}+\mathrm{Z}\mathrm{H}}$ ) for Run 2 and Run 3 (left), and two-dimensional likelihood scan as a function of the $\mathrm{W}\mathrm{W}\mathrm{Z}$ and ZH signal strength parameters for Run 2 and Run 3 (right). For the two-dimensional scan the one and two standard deviation ( $\sigma$ ) contours are indicated by the dotted and solid lines, respectively. In the signal strengths reported here, the uncertainty of the predicted cross section is not included.
png pdf	Figure 3-b: One-dimensional likelihood scan as a function of the inclusive $\mathrm{W}\mathrm{W}\mathrm{Z}$ and ZH signal strength parameter ( $\mu_{\mathrm{W}\mathrm{W}\mathrm{Z}+\mathrm{Z}\mathrm{H}}$ ) for Run 2 and Run 3 (left), and two-dimensional likelihood scan as a function of the $\mathrm{W}\mathrm{W}\mathrm{Z}$ and ZH signal strength parameters for Run 2 and Run 3 (right). For the two-dimensional scan the one and two standard deviation ( $\sigma$ ) contours are indicated by the dotted and solid lines, respectively. In the signal strengths reported here, the uncertainty of the predicted cross section is not included.
png pdf	Figure 4: Measured values of the $\mathrm{W}\mathrm{W}\mathrm{Z}$ , ZH, and inclusive signal strength parameters. Results are shown separately by run period as well as after combining the two datasets. In the signal strengths reported here, the uncertainty of the predicted cross section is not included.

Tables
png pdf	Table 1: Observed (expected) significance of the signal strength in units of standard deviations. The $\mathrm{W}\mathrm{W}\mathrm{Z}$ -only and ZH-only values are obtained by profiling the other signal process, together with all other nuisances.
png pdf	Table 2: Measured signal strengths and cross sections for the $\mathrm{W}\mathrm{W}\mathrm{Z}$ , ZH (with $\mathrm{H} \rightarrow \mathrm{W}\mathrm{W}$ ) and inclusive ( $\mathrm{W}\mathrm{W}\mathrm{Z}$ + $\mathrm{ZH}$ ) processes at $\sqrt{s} =$ 13 and 13.6 TeV. The last column shows the SM expectation. In the signal strengths reported here, the uncertainty of the predicted cross section is not included.

Summary

In summary, in this note we have presented a measurement of the

$\mathrm{p} \mathrm{p} \to \mathrm{W}\mathrm{W}\mathrm{Z}$ process in the four lepton final state in a dataset with an integrated luminosity of 200 fb

$^{-1}$ collected by the CMS Collaboration at center-of-mass energies of 13 and 13.6 TeV. The cross section relative to the standard model prediction is measured to be 1.03

$^{+0.31}_{-0.28}$ , representing the most precise measurement of this process to date, and provides the first evidence for a triboson production process at 13.6 TeV. Additionally, the non-resonant and ZH (with the Higgs boson decaying to W bosons) contributions are also studied simultaneously for the first time. Our results are in agreement with standard model predictions.

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