Comparison of LHC and ILC Capabilities for Higgs Boson Coupling Measurements

TL;DR

The paper evaluates how well LHC and ILC can determine Higgs boson couplings in a model‑independent framework based on deviation parameters d(A). It combines LHC and ILC observables within a naive Bayesian likelihood to produce 68% confidence intervals, using LHC 14 TeV 300 fb^-1 and staged ILC inputs (250/500/1000 GeV). It finds that the LHC alone faces significant challenges to reach sub‑5% precision due to Higgs width constraints, while the ILC can achieve sub‑3% precision across most couplings, with substantial gains from higher energies. The results underscore the complementary strengths of LHC and ILC for probing small deviations from SM predictions and guide future Higgs‑physics planning.

Abstract

I estimate the accuracies on Higgs boson coupling constants that experiments at the Large Hadron Collider and the International Linear Collider are capable of reaching over the long term.

Figures (2)

• Figure 1: Capabilities of LHC for model-independent measurements of Higgs boson couplings. The plot shows the 1 $\sigma$ confidence intervals for LHC at 14 TeV with 300 fb$^{-1}$ as they emerge from my fit. Deviation of the central values from zero indicates a bias, which can be corrected for. The upper limit on the $WW$ and $ZZ$ couplings arises from the constraints (\ref{['bound']}) and (\ref{['boundZ']}). No error is estimated for $g(hcc)$. The bar for the invisible channel gives the 1 $\sigma$ upper limit on the branching ratio. The marked horizontal band represents a 5% deviation from the Standard Model prediction for the coupling.
• Figure 2: Comparison of the capabilities of LHC and ILC for model-independent measurements of Higgs boson couplings. The plot shows (from left to right in each set of error bars) 1 $\sigma$ confidence intervals for LHC at 14 TeV with 300 fb$^{-1}$, for ILC at 250 GeV and 250 fb$^{-1}$ ('ILC1'), for the full ILC program up to 500 GeV with 500 fb$^{-1}$ ('ILC'), and for a program with 1000 fb$^{-1}$ for an upgraded ILC at 1 TeV ('ILCTeV'). More details of the presentation are given in the caption of Fig. \ref{['fig:resultsLHC']}. The marked horizontal band represents a 5% deviation from the Standard Model prediction for the coupling.