# Neutral Higgs decays $H \rightarrow Z \gamma,\gamma\gamma$ in 3-3-1 models

## TL;DR

This paper investigates how 3-3-1 models affect neutral Higgs boson decays into gamma gamma and Z gamma, highlighting the impact of new charged particles and model parameters on decay signals and deviations from Standard Model predictions.

## Contribution

It provides a detailed analysis of loop-induced Higgs decays in 3-3-1 models, including the effects of charged Higgs and gauge bosons, and explores the sensitivity of decay rates to model parameters.

## Key findings

- Large $v_3$ suppresses contributions from heavy particles, tightening bounds on decay signals.
- Lower $v_3$ allows significant contributions from heavy charged particles, leading to possible destructive or constructive interference.
- The branching ratio of a new neutral Higgs $h^0_3$ into gamma gamma is highly sensitive to the parameter $eta$.

## Abstract

The significance of new physics appearing in the loop-induced decays of neutral Higgs bosons into pairs of dibosons $\gamma\gamma$ and $Z\gamma$ will be discussed in the framework of the 3-3-1 models based on a recent work~\cite{Okada:2016whh}, where the Higgs sector becomes effectively the same as that in the two Higgs doublet models (2HDM) after the first symmetry breaking from $SU(3)_L$ scale into the electroweak scale. For large $SU(3)_L$ scale $v_3\simeq10$ TeV, dominant one-loop contributions to the two decay amplitudes arise from only the single charged Higgs boson predicted by the 2HDM, leading to that experimental constraint on the signal strength $\mu^{331}_{\gamma\gamma}$ of the Standard Model-like Higgs boson decay $h\rightarrow \gamma\gamma$ will result in a strict upper bound on the signal strength $\mu^{331}_{Z\gamma}$ of the decay $h\rightarrow\, Z\gamma$. For a particular model with lower $v_3$ around 3 TeV, contributions from heavy charged gauge and Higgs bosons may have the same order, therefore may give strong destructive or constructive correlations. As a by-product, a deviation from the SM prediction $|\mu^{331}_{\gamma\gamma}-1| \le 0.04$ still allows $|\mu^{331}_{Z\gamma}-1|$ to reach values near 0.1. We also show that there exists an $CP$-even neutral Higgs boson $h^0_3$ predicted by the 3-3-1 models, but beyond the 2HDM, has an interesting property that the branching ratio Br$(h^0_3\rightarrow \gamma\gamma)$ is very sensitive to the parameter $\beta$ used to distinguish different 3-3-1 models.