# Exploring Extended Scalar Sectors with Di-Higgs Signals: A Higgs EFT Perspective

## TL;DR

This paper investigates how extended scalar sectors influence Higgs self-interactions through effective field theory, constraining models with current data and exploring future collider sensitivities to deviations in Higgs self-couplings.

## Contribution

It identifies which extended scalar models generate the $|H|^6$ operator at tree level and assesses their constraints using LHC and electroweak data, projecting future collider sensitivities.

## Key findings

- Strong $T$ parameter constraints on triplet and quadruplet models.
- Potential for significant deviations in Higgs self-couplings in singlet and doublet models.
- Future 100 TeV collider data can probe all models' Higgs potential parameters.

## Abstract

We consider extended scalar sectors of the Standard Model as ultraviolet-complete motivations for studying the effective Higgs self-interaction operators of the Standard Model effective field theory. We investigate all motivated heavy scalar models which generate the dimension-6 effective operator, $|H|^6$, at tree level and proceed to identify the full set of tree-level dimension-six operators by integrating out the heavy scalars. Of seven models which generate $|H|^6$ at tree level only two, quadruplets of hypercharge $Y=3Y_H$ and $Y=Y_H$, generate only this operator. Next we perform global fits to constrain relevant Wilson coefficients from the LHC single Higgs measurements as well as the electroweak oblique parameters $S$ and $T$. We find that the $T$ parameter puts very strong constraints on the Wilson coefficient of the $|H|^6$ operator in the triplet and quadruplet models, while the singlet and doublet models could still have Higgs self-couplings which deviate significantly from the standard model prediction. To determine the extent to which the $|H|^6$ operator could be constrained, we study the dihiggs signatures at the future 100 TeV collider and explore future sensitivity of this operator. Projected onto the Higgs potential parameters of the extended scalar sectors, with $3$ ab$^{-1}$ luminosity data we will be able to explore the Higgs potential parameters in all seven models.