A second Higgs from the Higgs portal

TL;DR

This paper investigates the properties, constraints, and potential observability of a second Higgs boson arising from Higgs portal models, which could stabilize the electroweak vacuum and be detectable through specific decay channels.

Contribution

It provides a comprehensive analysis of the parameter space for a second Higgs in Higgs portal models, including stability, experimental constraints, and decay prospects.

Findings

Identifies parameter regions satisfying all experimental and stability constraints.

Shows the second Higgs can stabilize the electroweak vacuum.

Proposes decay channels for detecting the second Higgs at colliders.

Abstract

In the Higgs portal framework, the Higgs field generally mixes with the Standard Model singlet leading to the existence of two states, one of which is identified with the 125 GeV scalar observed at the LHC. In this work, we analyse direct and indirect constraints on the second mass eigenstate and the corresponding mixing angle. The existence of the additional scalar can be beneficial as it can stabilise the otherwise-metastable electroweak vacuum. We find parameter regions where all of the bounds, including the stability constraints, are satisfied. We also study prospects for observing the decay of the heavier state into a pair of the 125 GeV Higgs-like scalars.