# Direct Bounds on Heavy Top-Like Quarks With Standard and Exotic Decays

## TL;DR

This paper derives comprehensive bounds on heavy top-like quarks with arbitrary decay modes using LHC data, showing that masses below approximately 900 GeV are excluded regardless of decay channels, including exotic scalar decays.

## Contribution

It introduces a method to set bounds on heavy top-like quarks with any decay branching ratios using existing LHC searches, including decays into new scalars, and provides a supporting code.

## Key findings

- Heavy tops below ~900 GeV are excluded regardless of decay modes.
- Bounds are not weakened by the presence of new light scalars.
- A code automating the bounds derivation is provided.

## Abstract

Heavy vector-like quarks with electric charge $Q=2/3$ (also called \textit{heavy tops}) appear naturally in many extensions of the Standard Model. Although these typically predict the existence of further particles below the TeV scale, direct searches for heavy tops have been performed assuming that they decay only into SM particles. The aim of this paper is to overcome this situation. We consider the most constraining experimental LHC searches for vector-like quarks, including analyses of the 36 fb$^{-1}$ of data collected in the latest run at 13 TeV of center of mass energy, as well as searches sensitive to heavy tops decaying into a new scalar, $S$. Combining all these, we derive bounds for arbitrary values of the heavy top branching ratios. A simple code that automatizes this process is also provided. At the physics level, we demonstrate that bounds on heavy tops are not inevitably weaker in the presence of new light scalars. We find that heavy tops with masses below $\sim 900$ GeV are excluded by direct searches, independently of whether they decay into $Zt, Ht, Wb$ or $St$ (with $S$ giving either missing energy of bottom quarks) or into any combination of them.