Search for a 'stable alignment limit' in two Higgs-doublet models

TL;DR

This paper investigates the conditions under which the two Higgs-doublet model (2HDM) remains stable up to the Planck scale, emphasizing the role of a soft breaking parameter and the alignment limit in making the model highly predictive.

Contribution

It demonstrates that stability up to high scales requires a soft breaking parameter and constrains the model to depend on only two key parameters in the stable alignment limit.

Findings

Stability up to >10^{10} GeV requires a soft breaking parameter.

The 2HDM becomes fully determined by  and a mass parameter m_0.

The model is more predictive in the stable alignment limit.

Abstract

We study the conditions required to make the 2HDM scalar potential stable up to the Planck scale. The lightest CP-even scalar is assumed to have been found at the LHC and the {\em alignment limit} is imposed in view of the LHC Higgs data. We find that ensuring stability up to scales $\gtrsim 10^{10}$~GeV necessitates the introduction of a soft breaking parameter in the theory. Even then, some interesting correlations between the nonstandard masses and the soft breaking parameter need to be satisfied. Consequently, a 2HDM becomes completely determined by only two nonstandard parameters, namely, $\tb$ and a mass parameter, $m_0$, with $\tb \gtrsim 3$. These observations make a 2HDM, in the {\em stable alignment limit}, more predictive than ever.