# Searching for the heavy custodial fiveplet Higgs in the Georgi-Machacek model at the International Linear Collider

## TL;DR

This paper investigates the potential to discover heavy custodial fiveplet Higgs bosons in the Georgi-Machacek model at the ILC, focusing on their production, decay modes, and mass degeneracy testing.

## Contribution

It provides a detailed analysis of the detection prospects for H_5^{b0} and H_5^{0} scalars at the ILC, including decay channels and mass degeneracy considerations.

## Key findings

- Potential for discovering H_5^{b0} and H_5^{0} at the ILC.
- Identification of key decay modes for detection.
- Feasibility of testing mass degeneracy between charged and neutral scalars.

## Abstract

The Georgi-Machacek (GM) model is one of many Beyond Standard Model scenarios with an extended scalar sector which can group under the custodial $\rm SU(2)_C$ symmetry into a fiveplet, a triplet, and two singlets. The heavy charged custodial fiveplet Higgs $\rm H_5^{\pm}$ are typical particles in GM model which couple to the electroweak gauge bosons, therefore provide a good testing ground for the detection of the $\rm H^\pm W^\mp Z$ vertex. The neutral custodial fiveplet Higgs $\rm H_5^{0}$ in the GM model has the same mass with $\rm H_5^{\pm}$ and couples to the electroweak gauge bosons $\rm W^+ W^-$ and ZZ both. We study the discovery prospects of the exotic scalar bosons $\rm H_5^{\pm}$ and $\rm H_5^{0}$ at the International Linear Collider(ILC) via the vector boson associated production processes, and discuss two different decay modes for both charged and neutral scalars. The discovery potential is discussed. Testing the mass degeneracy of charged and neutral scalar bosons in the GM model is also considered.