CMS-HIG-23-007

CMS-HIG-23-007 ; CERN-EP-2024-123
Study of WH production through vector boson scattering and extraction of the relative sign of the W and Z couplings to the Higgs boson in proton-proton collisions at $ \sqrt{s} = $ 13 TeV
CMS Collaboration
26 May 2024
Accepted for publication in Phys. Lett. B
Abstract: A search for the production of a W boson and a Higgs boson through vector boson scattering (VBS) is presented, using CMS data from proton-proton collisions at $ \sqrt{s} = $ 13 TeV collected from 2016 to 2018. The integrated luminosity of the data sample is 138 fb$ ^{-1} $. Selected events must be consistent with the presence of two jets originating from VBS, the leptonic decay of the W boson to an electron or muon, and a Higgs boson decaying into a pair of b quarks, reconstructed as either a single merged jet or two resolved jets. A measurement of the process as predicted by the standard model (SM) is performed alongside a study of beyond-the-SM (BSM) scenarios. The SM analysis sets an observed (expected) 95% confidence level upper limit of 14.3 (9.0) on the ratio of the measured VBS WH cross section to that expected by the SM. The BSM analysis, conducted within the so-called $ \kappa $ framework, excludes all scenarios with $ \lambda_{\mathrm{W}\mathrm{Z}} < $ 0 that are consistent with current measurements, where $ \lambda_{\mathrm{W}\mathrm{Z}} = \kappa_{\mathrm{W}}/\kappa_{\mathrm{Z}} $ and $ \kappa_{\mathrm{W}} $ and $ \kappa_{\mathrm{Z}} $ are the HWW and HZZ coupling modifiers, respectively. The signficance of the exclusion is beyond 5 standard deviations, and it is consistent with the SM expectation of $ \lambda_{\mathrm{W}\mathrm{Z}} = $ 1.
Links: e-print arXiv:2405.16566 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ;

Figures & Tables	Summary	Additional Figures	References	CMS Publications

Figures
png pdf	Figure 1: Tree-level Feynman diagrams for the production of $ \mathrm{W}\mathrm{H}\to\ell\nu\mathrm{b}\overline{\mathrm{b}} $ via VBS, where $ \ell $ is an electron or muon.
png pdf	Figure 1-a: Tree-level Feynman diagrams for the production of $ \mathrm{W}\mathrm{H}\to\ell\nu\mathrm{b}\overline{\mathrm{b}} $ via VBS, where $ \ell $ is an electron or muon.
png pdf	Figure 1-b: Tree-level Feynman diagrams for the production of $ \mathrm{W}\mathrm{H}\to\ell\nu\mathrm{b}\overline{\mathrm{b}} $ via VBS, where $ \ell $ is an electron or muon.
png pdf	Figure 1-c: Tree-level Feynman diagrams for the production of $ \mathrm{W}\mathrm{H}\to\ell\nu\mathrm{b}\overline{\mathrm{b}} $ via VBS, where $ \ell $ is an electron or muon.
png pdf	Figure 2: Distributions of the scalar sum of the Higgs boson and W boson $ p_{\mathrm{T}} $, as generated by MADGRAPH, for simulated signal events with $ \kappa_{\mathrm{Z}}= $ 1 and the following $ \kappa_{\mathrm{W}} $ values: $ \kappa_{\mathrm{W}}= $ 1 (SM) in light blue (filled), $ \kappa_{\mathrm{W}}= $ 0.5 in dark blue, $ \kappa_{\mathrm{W}}= $ 0 in yellow, and $ \kappa_{\mathrm{W}}=- $1 in gold. The highest bin also contains the overflows.
png pdf	Figure 3: Event yields observed in the data (black points) for regions A, B, C, and D of the BSM analysis, where region A is the signal region. The simulated SM background event yields in the control regions B, C, and D are shown in light blue. The background in the signal region estimated from data in regions B, C, and D is plotted in dark blue. The lower panel shows the ratio of the data to the estimated background yields. The vertical bars on the points give the statistical uncertainty in the data, while the gray and hatched areas represent the statistical and total uncertainties in the estimated backgrounds, respectively.
png pdf	Figure 4: Observed and expected distributions of the BDT output in the signal region of the SM analysis. The data are shown by the points and the expected contributions from the various sources after the fit to the data by the colored histograms. The lower plot displays the ratio of the data to the sum of the predicted distributions. The vertical bars on the points indicate the statistical uncertainty in the data, and the hatched regions show the systematic uncertainty in the sum of the predicted yields. The rightmost bin includes overflow.
png pdf	Figure 5: The $ > $95% (2$ \,\sigma $) and $ > $99.99% (5$ \,\sigma $) exclusion regions in the two-dimensional $ \kappa_{\mathrm{W}}-\kappa_{\mathrm{Z}} $ plane are shown by the dark and light blue colors, respectively. Previous CMS measurements of the magnitude of $ \kappa_{\mathrm{W}} $ and $ \kappa_{\mathrm{Z}} $ at the 95% CL [8] are represented by the horizontal and vertical bars, and the SM expectation is given by the gold star.

Tables

png pdf

Table 1:
The background yield estimated from data and signal yield ($ \kappa_{\mathrm{W}}=- $1, $ \kappa_{\mathrm{Z}}= $ 1) predicted by MC simulation in the BSM signal region are shown with their associated statistical and systematic uncertainties. The systematic uncertainty in the signal yield quoted here is the sum in quadrature of the independent relative systematic uncertainties, multiplied by the total yield. The observed data yield is also tabulated.

Summary

In this Letter, we have reported the first study of WH production through vector boson scattering (VBS) using 138 fb$ ^{-1} $ of data recorded with the CMS detector at the LHC between 2016 and 2018 at a center-of-mass energy of 13 TeV. We focused on both the standard model (SM) scenario and scenarios where $ \lambda_{\mathrm{W}\mathrm{Z}}=\kappa_{\mathrm{W}}/\kappa_{\mathrm{Z}} $, with $ \kappa_{\mathrm{W}} $ and $ \kappa_{\mathrm{Z}} $ being the HWW and HZZ coupling modifiers, respectively, is modified from the SM value of 1. Events were selected by requiring exactly one isolated charged lepton (electron or muon) and the magnitude of the missing transverse momentum $ p_{\mathrm{T}}^\text{miss} $ being consistent with the W boson leptonic decay, two jets consistent with a VBS interaction, and one or two additional jets consistent with the Higgs boson decay to $ \mathrm{b} \overline{\mathrm{b}} $. Assuming a signal with SM features, the observed (expected) ratio between the measured rate of VBS WH and the expectation from the SM is 3.0 $ ^{+5.9}_{-5.5} $ (1.0$^{+4.3}_{-4.0}$), corresponding to an observed (expected) 95% confidence level upper limit of 14.3 (9.0) times the SM prediction. The BSM scenario where $ \lambda_{\mathrm{W}\mathrm{Z}} = - $1, with $ |\kappa_{\mathrm{W}}| = |\kappa_{\mathrm{Z}}| = $ 1, and all the opposite-sign scenarios with $ \kappa_{\mathrm{W}} $ and $ \kappa_{\mathrm{Z}} $ values compatible with the current measurements are excluded with a significance greater than 5 standard deviations, corresponding to a confidence level higher than 99.99%.

Additional Figures
png pdf	Additional Figure 1: A scan of $ -2\Delta\ln{L} $, where $ L $ is the likelihood, for the SM analysis plotted as a function of the signal strength $ \mu $ for the expected (red) and the observed (black) data.
png pdf	Additional Figure 2: Observed and expected distributions of the VBS dijet mass in the $ \mathrm{t} \overline{\mathrm{t}} $ control region of the SM analysis. The data are shown by the points and the expected contributions from the various sources after the fit to the data by the colored histograms. The lower plot displays the ratio of the data to the sum of the predicted distributions. The vertical bars on the points indicate the statistical uncertainty in the data, and the hatched regions show the systematic uncertainty in the sum of the predicted yields.
png pdf	Additional Figure 3: Observed and expected distributions of the W$+$jets BDT output in the W$+$jets control region of the SM analysis. The data are shown by the points and the expected contributions from the various sources after the fit to the data by the colored histograms. The lower plot displays the ratio of the data to the sum of the predicted distributions. The vertical bars on the points indicate the statistical uncertainty in the data, and the hatched regions show the systematic uncertainty in the sum of the predicted yields.
png pdf	Additional Figure 4: A scan of $ -2\Delta\ln{L} $, where $ L $ is the likelihood, for the BSM analysis plotted as a function of the signal strength $ \mu $ for the observed data, with the $ \mu $ values excluded at the 68% $ \text{CL} (1\,\sigma) $ labeled.
png pdf	Additional Figure 5: The exclusion significance in the BSM analysis for $ \mu = $ 1, where $ \mu $ is the signal strength, plotted as a function of $ \kappa_{\mathrm{W}} $ and $ \kappa_{\mathrm{Z}} $ with the 2 $ \,\sigma $ contour boundary overlaid.
png pdf	Additional Figure 6: The $ M_{\mathrm{SD}} $ distribution for the BSM analysis in region A ($ M_{\mathrm{SD}} < $ 150 GeV) and region D ($ M_{\mathrm{SD}} \geq $ 150 GeV). The signal, with $ \kappa_{\mathrm{W}} = - $1 and $ \kappa_{\mathrm{Z}} = + $1, is plotted in red.
png pdf	Additional Figure 7: The $ M_{\mathrm{SD}} $ distribution for the BSM analysis in region B ($ M_{\mathrm{SD}} < $ 150 GeV) and region C ($ M_{\mathrm{SD}} \geq $ 150 GeV). The signal, with $ \kappa_{\mathrm{W}} = - $1 and $ \kappa_{\mathrm{Z}} = + $1, is plotted in red.

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