# Electroweak production of multiple (pseudo)scalars in the 2HDM

## TL;DR

This paper investigates the electroweak production of multiple (pseudo)scalar Higgs bosons in the 2HDM, highlighting the potential dominance of electroweak processes over QCD in certain final states and their importance for probing Higgs couplings.

## Contribution

It compares electroweak and QCD production channels of multi-Higgs states in the 2HDM, revealing scenarios where electroweak processes dominate and can probe otherwise inaccessible couplings.

## Key findings

- Electroweak production can surpass QCD in certain multi-Higgs final states.
- Charged Higgs final states are uniquely accessible via electroweak processes.
- Some parameter regions are consistent with current experimental constraints.

## Abstract

The two-Higgs Doublet Model (2HDM) is the most minimal extension of the Standard Model (SM) containing extra Higgs doublet fields. Given the multiplicity of Higgs states in a 2HDM, its Higgs potential is significantly more involved than the SM one. Importantly, it contains a multitude of Higgs triple self-couplings, unlike the SM, which only has one. These interactions are key to understanding the phenomenology of the 2HDM, as they uniquely determine the form of the potential. Several studies analysing the prospects of measuring these couplings at the Large Hadron Collider (LHC) have found them to be quite low generally. However, such studies have largely concentrated on Higgs pair-production induced by gluon-gluon scattering, either via direct annihilation or followed by their splitting into $b$-(anti)quark pairs, which in turn annihilate leaving behind spectator $b$-(anti)quarks. Both of these channels are therefore governed by QCD dynamics. We compare here the yields of such channels to those initiated by (primarily) valence quarks, which involve Electro-Weak (EW) interactions only, for neutral multi-Higgs final states. We find that EW production can be dominant over QCD production for certain final state combinations. We also illustrate that charged final states, which can only be produced via EW modes, could serve as important probes of some $H^\pm$ triple couplings, that are inaccessible in QCD-induced processes, during Run 2 and 3 of the LHC. Our analysis covers regions of the parameter space of the Type-I 2HDM that have escaped the most up-to-date experimental constraints coming from EW precision data, LHC measurements of the 125 GeV Higgs boson properties, searches for additional Higgs states, and flavour physics.