# Cascade decays of Heavy Higgs bosons through vectorlike quarks

## TL;DR

This paper investigates heavy Higgs boson cascade decays via vectorlike quarks, extending LHC sensitivity to larger masses, and explores the potential for discovering new Higgs and quarks through these channels.

## Contribution

It introduces new decay modes of heavy Higgs bosons involving vectorlike quarks, analyzing their significance and LHC discovery prospects in various scenarios.

## Key findings

- Decay modes can dominate in certain parameter regions.
- LHC can probe cross sections as low as 0.1 fb for specific decay channels.
- Higgs cascade decay rates can surpass single vectorlike quark production rates.

## Abstract

We study cascade decays of heavy neutral Higgs bosons through vectorlike quarks. We focus on scenarios where decay modes into pairs of vectorlike quarks are not kinematically open which extends the sensitivity of the LHC to larger masses. Assuming only mixing with the third family of standard model quarks the new decay modes of heavy Higgs bosons are: $H\to t_4 t \to Wbt, Zt t, ht t$ and $H\to b_4 b \to Wtb, Zb b, hb b$, where $t_4$ ($b_4$) is the new up-type (down-type) quark mass eigenstate. In the numerical analysis we assume the CP even Higgs boson in the two Higgs doublet model type-II but the signatures are relevant for many other scenarios. We identify the region of the parameter space where these decay modes are significant or can even dominate, and thus they provide the best opportunities for the simultaneous discovery of a new Higgs boson and vectorlike quarks. We further explore the reach of the High Luminosity LHC for two representative decay modes, $t_4\to Zt\to\ell\ell t$ and $b_4\to Zb\to\ell\ell b$, and found that cross sections at a 0.1 fb level can be probed with simple cut based analyses. We also find that the rates for Higgs cascade decays can be much larger than the rates for a single production of vectorlike quarks. Furthermore, the reach for vectorlike quarks in Higgs cascade decays and pair production extends to comparable masses.