Model-independent analysis of Higgs spin and CP properties in the process $e^+ e^- \to t \bar t \Phi$

TL;DR

This paper presents a model-independent analysis of the Higgs boson's spin and CP properties in association with top quark pairs at high-energy electron-positron colliders, using multiple observables to improve determination accuracy.

Contribution

It introduces a comprehensive method combining various observables to determine Higgs CP properties and spin in a model-independent manner at future colliders.

Findings

Combining multiple observables significantly reduces errors in CP property determination.

Top polarization asymmetry and cross section ratios are sensitive to the Higgs spin.

The analysis enhances the understanding of Higgs couplings in a model-independent framework.

Abstract

In this paper we investigate methods to study the $t\bar{t}$ Higgs coupling. The spin and CP properties of a Higgs boson are analysed in a model-independent way in its associated production with a $t\bar{t}$ pair in high-energy $e^+e^-$ collisions. We study the prospects of establishing the CP quantum numbers of the Higgs boson in the CP-conserving case as well as those of determining the CP-mixing if CP is violated. We explore in this analysis the combined use of the total cross section and its energy dependence, the polarisation asymmetry of the top quark and the up-down asymmetry of the antitop with respect to the top-electron plane. We find that combining all three observables remarkably reduces the error on the determination of the CP properties of the Higgs Yukawa coupling. Furthermore, the top polarisation asymmetry and the ratio of cross sections at different collider energies are shown to be sensitive to the spin of the particle produced in association with the top quark pair.