Measuring Higgs Boson Self-couplings with $2\rightarrow 3$ VBS Processes

TL;DR

This paper investigates the potential of $2 ightarrow 3$ vector boson scattering processes to measure Higgs self-couplings within SMEFT at future colliders, highlighting their energy-dependent sensitivity and experimental challenges.

Contribution

It introduces a comprehensive analysis of $2 ightarrow 3$ VBS processes for Higgs self-coupling measurement, emphasizing their significance at high-energy colliders and proposing polarization and cut strategies.

Findings

Energy enhancement of SMEFT contributions with $E^2/\, ext{Lambda}^2$

WWh process is as crucial as triple Higgs production for measurements

High-energy colliders like 100 TeV pp and muon colliders are promising for these studies

Abstract

We study the measurement of Higgs boson self-couplings through $2\rightarrow 3$ vector boson scattering (VBS) processes in the framework of Standard Model effective field theory (SMEFT) at both proton and lepton colliders. The SMEFT contribution to the amplitude of the $2\to3$ VBS processes, taking $W_L W_L\rightarrow W_L W_L h$ and $W_L W_L\rightarrow h h h$ as examples, exhibits enhancement with the energy $\frac{\mathcal{A}^{\text{BSM}}}{\mathcal{A}^{\text{SM}}} \sim \frac{E^2}{\Lambda^2}$, which indicates the sensitivity of these processes to the related dimension-six operators in SMEFT. Simulation of the full processes at both hadron and lepton colliders with a variety of collision energies are performed to estimate the allowed region on $c_6$ and $c_{\Phi_1}$. Especially we find that, with the help of exclusively choosing longitudinal polarizations in the final states and suitable $p_T$ cuts, $WWh$ process is as important as the more widely studied triple Higgs production ($hhh$) in the measurement of Higgs self-couplings. Our analysis indicates that these processes can play important roles in the measurement of Higgs self-couplings at future 100 TeV pp colliders and muon colliders. However, their cross sections are generally tiny at low energy machines, which makes them much more challenging to explore.