Tree-level unitarity constraints in the 2HDM with CP-violation

TL;DR

This paper derives tree-level unitarity constraints for the 2HDM with explicit CP-violation, focusing on soft Z_2 symmetry breaking and leveraging rephasing invariance, providing a method applicable to other Higgs models.

Contribution

It introduces a simple, transferable approach to derive unitarity constraints in the 2HDM with CP-violation, emphasizing rephasing invariance and soft symmetry breaking.

Findings

Derived unitarity bounds for 2HDM with CP-violation

Highlighted the role of rephasing invariance in constraints

Discussed implications of unitarity violation on physical theory content

Abstract

We obtain tree-level unitarity constraints for the Two Higgs Doublet Model (2HDM) with explicit CP-violation. We limit ourselves to the case with soft violation of the discrete Z_2 symmetry of theory. The key role is played by the rephasing invariance of the 2HDM lagrangian. Our simple approach for derivation of these constraints can be easily transferred to other forms of Higgs sector. We briefly discuss correspondence between possible violation of tree level unitarity limitation and physical content of theory.