# Theory and Phenomenology of Two Higgs Doublet Type-II Seesaw Model at the LHC Run-2

## TL;DR

This paper explores the Two Higgs Doublet Model extended with a complex triplet scalar, analyzing its theoretical constraints and phenomenology, and identifying potential signals at the LHC to distinguish triplet contributions.

## Contribution

It provides a comprehensive theoretical and phenomenological analysis of the 2HDMcT model, including unitarity, boundedness constraints, and LHC observable predictions.

## Key findings

- Triplet admixtures can still fit Higgs data.
- New production and decay channels are identified.
- Parameter space compatible with current constraints.

## Abstract

We study the most popular scalar extension of the Standard Model, namely the Two Higgs doublet model, extended by a complex triplet scalar (2HDMcT). Such considering model with a very small vacuum expectation value, provides a solution to the massive neutrinos through the so-called type II seesaw mechanism. We show that the 2HDMcT enlarged parameter space allow for a rich and interesting phenomenology compatible with current experimental constraints. In this paper the 2HDMcT is subject to a detailed scrutiny. Indeed, a complete set of tree level unitarity constraints on the coupling parameters of the potential is determined, and the exact tree-level boundedness from below constraints on these couplings are generated for all directions. We then perform an extensive parameter scan in the 2HDMcT parameter space, delimited by the above derived theoretical constraints as well as by experimental limits. We find that an important triplet admixtures are still compatible with the Higgs data and investigate which observables will allow to restrict the triplet nature most effectively in the next runs of the LHC. Finally, we emphasize new production and decay channels and their phenomenological relevance and treatment at the LHC.