# New Physics in Double Higgs Production at Future $e^+ e^-$ Colliders

## TL;DR

This paper investigates how new physics, via dimension-six operators, could enhance double Higgs production at future electron-positron colliders, identifying key operators and estimating experimental sensitivities.

## Contribution

It identifies two relevant effective operators affecting double Higgs production and evaluates their potential detectability at upcoming colliders.

## Key findings

- Two key operators are not yet strongly constrained by existing data.
- Sensitivity estimates for operator coefficients at various future collider scenarios.
- Expected 95% confidence level limits for different energy and luminosity benchmarks.

## Abstract

We study the effects of new physics in double Higgs production at future $e^+ e^-$ colliders. In the Standard Model the chiral limit ($m_e=0$) plays an important role for this process, being responsible for the smallness of the tree-level diagrams with respect to the 1-loop contributions. In our work, we consider the possibility of an enhancement due to the contribution of Standard Model dimension-six effective operators. We show that there are only two relevant operators for this process that are not yet (strongly) constrained by other data. We perform a sensitivity study on the operator coefficients for several benchmark values of energy and integrated luminosity related to the proposed linear colliders such as CLIC, ILC and FCC-ee and we derive expected 95% CL limits for each benchmark scenario.