Higgs Squared

TL;DR

This paper introduces a new Higgs-VEV sensitive operator within an extended two Higgs doublet model, reducing tuning in cosmic selection models for the electroweak hierarchy problem and enabling novel neutrino mass mechanisms.

Contribution

It presents a unique operator construction based on a 2HDM with a softly broken $D_8$ symmetry, reducing tuning and connecting to neutrino mass generation.

Findings

Operator reduces tuning in hierarchy models

Model naturally approaches the alignment limit

Extended Higgs sector enables a new neutrino seesaw mechanism

Abstract

We present a novel construction for a Higgs-VEV sensitive operator, which can be used as a trigger operator in cosmic selection models for the electroweak hierarchy problem. Our operator does not contain any degrees of freedom charged under the SM gauge symmetries, leading to reduced tuning in the resulting models. Our construction is based on the extension of a two Higgs doublet model (2HDM) with a softly broken approximate global $D_8$ symmetry (the symmetry group of a square). A cosmic crunching model based on our extended Higgs sector has only a percent level tuning corresponding to the usual little hierarchy problem. In large regions of parameter space the 2HDM is naturally pushed towards the alignment limit. A complete model requires the introduction of fermionic top partners to ensure the approximate $D_8$ symmetry in the fermion sector. We also show that the same extended Higgs sector can be used for a novel implementation of the seesaw mechanism of neutrino masses.