Model-Independent Determination of the Triple Higgs Coupling at $e^+e^-$ Colliders

TL;DR

This paper demonstrates a method to determine the triple Higgs coupling independently of specific models at future $e^+e^-$ colliders by combining multiple measurements and using effective field theory parameters.

Contribution

It introduces a model-independent approach to extract the triple Higgs coupling using combined measurements and EFT parameters at a 500 GeV $e^+e^-$ collider.

Findings

Model-independent limits on the EFT parameter c6 are achievable.

Combining measurements improves precision of Higgs coupling constants.

Full simulation estimates support the feasibility of the method.

Abstract

The observation of Higgs pair production at high-energy colliders can give evidence for the presence of a triple Higgs coupling. However, the actual determination of the value of this coupling is more difficult. In the context of general models for new physics, double Higgs production processes can receive contributions from many possible beyond-Standard-Model effects. This dependence must be understood if one is to make a definite statement about the deviation of the Higgs field potential from the Standard Model. In this paper, we study the extraction of the triple Higgs coupling from the process $e^+e^-\to Zhh$. We show that, by combining the measurement of this process with other measurements available at a 500 GeV $e^+e^-$ collider, it is possible to quote model-independent limits on the Effective Field Theory parameter c6 that parametrizes modifications of the Higgs potential. We present precise error estimates based on the anticipated ILC physics program, studied with full simulation. Our analysis also gives new insight into the model-independent extraction of the Higgs boson coupling constants and total width from $e^+e^-$ data.