# Approximate Alignment in Two Higgs Doublet Model with Extra Yukawa Couplings

## TL;DR

This paper explores how a two Higgs doublet model with extra Yukawa couplings can naturally explain the observed Higgs boson properties, potentially enable electroweak baryogenesis, and suggests new particles could be detectable at the LHC.

## Contribution

It introduces a scenario where Higgs quartic couplings are of order one, linking alignment with new physics and proposing testable predictions for collider experiments.

## Key findings

- Alignment can arise with Higgs quartic couplings of order one.
- Extra top Yukawa couplings can facilitate electroweak baryogenesis.
- Exotic Higgs bosons may be sub-TeV and yet undetected at current colliders.

## Abstract

With discovery of the 125 GeV boson $h^0$, the existence of a second doublet is very plausible. We show that the "alignment" phenomenon, that $h^0$ is found to resemble closely the Standard Model Higgs boson, may correspond to Higgs quartic couplings $\eta_i$ that are ${\cal O}(1)$ in strength. If the exotic bosons of the second doublet possess extra top Yukawa couplings, which are the least constrained by data, such a two Higgs doublet model could drive electroweak baryogenesis, as well as further "protect" the apparent alignment. The exotic Higgs bosons can be sub-TeV in mass while remaining well hidden so far, with broad parameter space for search at the Large Hadron Collider.