Light scalars in the Weinberg 3HDM potential with spontaneous CP violation

TL;DR

This paper investigates the Weinberg 3HDM potential, highlighting its capacity for spontaneous CP violation and the emergence of light scalar bosons, with implications for extended Higgs sector phenomenology.

Contribution

It demonstrates that the Weinberg 3HDM potential can naturally produce light scalars and small CP-violating effects due to an approximate global symmetry, supported by parameter space analysis.

Findings

Presence of light additional Higgs bosons below the SM-like Higgs mass.

Small CP-violating effects due to approximate U(1) x U(1) symmetry.

Model accommodates both explicit and spontaneous CP violation.

Abstract

The $\mathbb Z_2\times \mathbb Z_2$-symmetric 3HDM potential, sometimes called Weinberg's 3HDM potential, can accommodate both explicit and spontaneous CP violation as well as natural flavour conservation and is hence relevant for studies of CP violation coming from a realistic extended Higgs sector. The model has an interesting regime, controlled by a single parameter, where it acquires an approximate global $U(1) \times U(1)$ symmetry which causes CP violating effects to be small and two pseudo-Goldstone bosons to be present in the scalar spectrum. From parameter space scans, we find that, in a realistic implementation featuring an SM-like Higgs boson, this model predominantely leads to the existence of light additional Higgs bosons with a mass lower than the SM-like Higgs boson.