Electroweak Couplings of the Higgs Boson at a Multi-TeV Muon Collider

TL;DR

This paper evaluates how precisely a multi-TeV muon collider can measure Higgs boson couplings to electroweak gauge bosons and the Higgs self-coupling, highlighting the potential to probe new physics at multi-TeV scales.

Contribution

It introduces a detailed analysis of Higgs coupling measurements at high-energy muon colliders, including strategies to distinguish between different fusion processes and sensitivity estimates for new physics scales.

Findings

Achieves 95% CL sensitivity of 0.073% for WWH coupling at 10 TeV

Probes new physics scales up to 10 TeV at 10 TeV collider

Provides a framework for analyzing Higgs self-coupling and quartic couplings

Abstract

We estimate the expected precision at a multi-TeV muon collider for measuring the Higgs boson couplings with electroweak gauge bosons, $HVV$ and $HHVV\ (V=W^\pm,Z)$, as well as the trilinear Higgs self-coupling $HHH$. At very high energies both single and double Higgs productions rely on the vector-boson fusion (VBF) topology. The outgoing remnant particles have a strong tendency to stay in the very forward region, leading to the configuration of the "inclusive process" and making it difficult to isolate $ZZ$ fusion events from the $WW$ fusion. In the single Higgs channel, we perform a maximum likelihood analysis on $HWW$ and $HZZ$ couplings using two categories: the inclusive Higgs production and the 1-muon exclusive signal. In the double Higgs channel, we consider the inclusive production and study the interplay of the trilinear $HHH$ and the quartic $VVHH$ couplings, by utilizing kinematic information in the invariant mass spectrum. We find that at a centre-of-mass energy of 10 TeV (30 TeV) with an integrated luminosity of 10 ab$^{-1}$ (90 ab$^{-1}$), one may reach a 95\% confidence level sensitivity of 0.073\% (0.023\%) for $WWH$ coupling, 0.61\% (0.21\%) for $ZZH$ coupling, 0.62\% (0.20\%) for $WWHH$ coupling, and 5.6\% (2.0\%) for $HHH$ coupling. For dim-6 operators contributing to the processes, these sensitivities could probe the new physics scale $\Lambda$ in the order of $1-10$ ($2-20$) TeV at a 10 TeV (30 TeV) muon collider.