Measuring the Higgs-Vector boson Couplings at Linear $e^{+} e^{-}$ Collider

TL;DR

This paper evaluates how precisely future linear electron-positron colliders can measure Higgs-vector boson couplings by analyzing multiple production processes and kinematic distributions, considering different energies and beam polarizations.

Contribution

It introduces a comprehensive analysis using optimal observables across five processes to estimate measurement accuracies of Higgs couplings at various collider energies and polarization settings.

Findings

Quantifies statistical errors on effective couplings at different energies.

Provides correlations among coupling measurements.

Analyzes impact of beam polarization on measurement precision.

Abstract

We estimate the accuracy with which the coefficient of the CP even dimension six operators involving Higgs and two vector bosons (HVV) can be measured at linear $e^+ e^-$ colliders. Using the optimal observables method for the kinematic distributions, our analysis is based on the five different processes. First is the WW fusion process in the t-channel ($e^+e^- \to \bar{\nu}_e \nu_e H$), where we use the rapidity y and the transverse momentum $\pT$ of the Higgs boson as observables. Second is the ZH pair production process in the s-channel, where we use the scattering angle of the Z and the Z decay angular distributions, reproducing the results of the previous studies. Third is the t-channel ZZ, fusion processes ($e^+e^- \to e^+e^ -H$), where we use the energy and angular distributions of the tagged $e^+$ and $e^-$. In the fourth, we consider the rapidity distribution of the untagged $e^+e^-H$ events, which can be approximated well as the $\gamma \gamma$ fusion of the bremsstrahlung photons from $e^+$ and $e^-$ beams. As the last process,we consider the single tagged $e^+e^- H$ events, which probe the $\gamma e^{\pm} \to H e^{\pm}$ process. All the results are presented in such a way that statistical errors of the constraints on the effective couplings and their correlations are read off when all of them are allowed to vary simultaneously, for each of the above processes, for $m_H=120 $ GeV, at $\sqrt{s}=250\GEV$, $350\GEV$ $500\GEV$ and $1\TEV$, with and without $e^-$ beam polarization of 80%.