LHC Signatures of Neutral Scalar Cascades in the $Z_3$ symmetric 3HDM

TL;DR

This paper investigates the collider signatures of neutral scalar cascade decays in the $Z_3$ symmetric 3HDM at the LHC, analyzing two mass hierarchy scenarios and their potential for discovery.

Contribution

It provides a detailed collider phenomenology analysis of the 3HDM with $Z_3$ symmetry, focusing on cascade decay signatures and their detectability at the LHC.

Findings

Medial Hierarchy scenario allows discovery-level sensitivity for scalars.

Regular Hierarchy requires higher luminosity for similar sensitivity.

Cross-section analysis across multiple benchmark points.

Abstract

Extending the scalar sector is one of the standard approaches to exploring scenarios beyond the Standard Model. In this work, we examine the collider phenomenology of the Three Higgs Doublet Model (3HDM) in the Type-Z or the democratic Yukawa interaction setup at the LHC. The scalar spectrum of the 3HDM includes three CP-even scalars, two CP-odd scalars, and four charged Higgs bosons. Focusing on cascade decay topologies, we investigate the collider signatures of the neutral scalars through the process $pp \rightarrow SV$, where $S$ is a neutral scalar and $V$ is a vector boson. We perform a cross-section analysis across multiple benchmark points that satisfy both theoretical and experimental constraints, considering two mass hierarchy scenarios: (i) Regular Hierarchy, where the SM-like Higgs is the lightest CP-even scalar, and (ii) Medial Hierarchy, featuring one Higgs boson lighter than the SM Higgs and one heavier. For both scenarios, we study the specific process $pp \rightarrow A \rightarrow HZ \rightarrow b \bar{b} l^+l^-$, performing a cut and count analysis at $\sqrt{s}=14$ TeV. Our results demonstrate that while the Medial Hierarchy scenario allows discovery-level sensitivity for both the CP-even and CP-odd scalars, achieving the same sensitivity in the Regular Hierarchy setup necessitates substantially higher luminosity.