Prospects for Measuring the Higgs Boson Decay to $WW^{*}$ in Fully Hadronic Final States at the ILC Using Multivariate Techniques

TL;DR

Problem: quantify the statistical potential to measure $\sigma(HZ)\times BR(H\rightarrow WW^{*})$ in the fully hadronic $HZ$ final state at the ILC. Approach: a full detector-level study with the ILD model at $\sqrt{s}=250$ and $500$ GeV, six-jet reconstruction, and multivariate (BDT) selection using realistic beam polarization and overlay. Findings: relative uncertainties of $4.1\%$ at $250$ GeV and $6.5\%$ at $500$ GeV for $500\,\mathrm{fb}^{-1}$, improving to $2.0\%$ and $2.3\%$ under the ILC H20 luminosity scenario; combining energy stages in a global fit yields the Higgs-$W$ coupling precision. Significance: demonstrates feasibility of precision measurements in fully hadronic Higgs decays at the ILC and informs future coupling fits.

Abstract

In this paper, the statistical potential of the measurement of Higgs to $WW^{*}$ decay at the International Linear Collider (ILC) is presented. The Higgs boson with a mass of 125 GeV is produced through the Higgsstrahlung production channel. The study is conducted at two center-of-mass energies, 250 and 500 GeV. The fully hadronic final state is analyzed. The analysis is performed on Monte Carlo data samples obtained using detailed ILD detector simulation, assuming an integrated luminosity of 500 fb$^{-1}$ and maximal beam polarization of both beams, $P(e^{+}e^{-}) = (+0.3, -0.8)$. The background from $γγ\to$ hadron processes is overlaid on each event. Analyses are performed using machine learning. The obtained relative statistical uncertainties of the measurement are 4.1% and 6.5% at 250 and 500 GeV, respectively.

Figures (4)

• Figure 1: The cross section distributions of the Higgs boson production processes at the electron-positron colliders, as a function of the center of mass energy, for polarized beams $P(e^+e^-) = (+0.2,-0.8)$. The dominant Higgs production channels, the Higgsstrahlung and WW-fusion are depicted by the red and blue lines, respectively.
• Figure 2: Distribution of the reconstructed invariant mass for the Z and W boson.
• Figure 3: Reconstructed distributions of the event shape variable thrust, for signal (black) and backgrounds (colors) events after preselection (left) and final selection (right). Distributions have been rescaled to allow for direct shape comparison; the original event counts are not preserved.
• Figure 4: Distribution of the reconstructed invariant mass for the Z boson candidate for signal (black) and background (colors) after preselection (left) and final selection (right).