# Reopen parameter regions in Two-Higgs Doublet Models

## TL;DR

This paper investigates how radiative corrections can expand the parameter space of Two-Higgs Doublet Models by restoring vacuum stability in regions previously considered unstable at tree-level.

## Contribution

It demonstrates that loop corrections significantly reopen parameter regions in THDM type-II that are excluded by tree-level stability constraints.

## Key findings

- Loop corrections revive over 50% of previously excluded points.
- Radiative effects are likely important in other standard model extensions.
- Tree-level analyses may underestimate viable parameter space.

## Abstract

The stability of the electroweak potential is a very important constraint for models of new physics. At the moment, it is standard for Two-Higgs doublet models (THDM), singlet or triplet extensions of the standard model to perform these checks at tree-level. However, these models are often studied in the presence of very large couplings. Therefore, it can be expected that radiative corrections to the potential are important. We study these effects at the example of the THDM type-II and find that loop corrections can revive more than 50% of the phenomenological viable points which are ruled out by the tree-level vacuum stability checks. Similar effects are expected for other extension of the standard model.