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

TL;DR

This paper reports a search for W and Higgs boson production via vector boson scattering at 13 TeV, measuring the process and testing the relative sign of W and Z couplings to the Higgs, confirming the Standard Model predictions.

Contribution

First measurement of VBS-induced WH production at 13 TeV, including constraints on the relative sign of W and Z Higgs couplings, with results consistent with the Standard Model.

Findings

Observed upper limit of 14.3 on SM cross section ratio

Excludes negative W/Z coupling scenarios with >5 sigma significance

Results support the Standard Model prediction of positive W/Z coupling ratio

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, possibly also through an intermediate $\tau$ lepton, 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 (9.9) 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 $\lambda_\mathrm{WZ}$ $\lt$ 0 that are consistent with current measurements, where $\lambda_\mathrm{WZ}$ = $\kappa_\mathrm{W} / \kappa_\mathrm{Z}$ 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 $\lambda_\mathrm{WZ}$ = 1.