# Implications of Four-Top and Top-Pair Studies on Triple-Top Production

## TL;DR

This paper explores how studies of four-top and top-pair production at the LHC can inform triple-top production, which is a rare process sensitive to new physics, especially within the general two Higgs doublet model.

## Contribution

It demonstrates the potential of four-top search regions to constrain triple-top production and highlights the role of g2HDM in enhancing triple-top signals beyond the Standard Model.

## Key findings

- Triple-top production cross section can reach pb level in g2HDM.
- Certain four-top search regions can be used to constrain triple-top production.
- CMS 13 TeV data may indicate new physics consistent with g2HDM.

## Abstract

Multi-top quark production is a staple program at the LHC. Single-top and $t\bar t$ productions are studied extensively, while current efforts are zooming in on four-top search, where the Standard Model (SM) cross section is at ${\cal O}(10)$ fb. In contrast, only at the fb level in SM, triple-top production has not been targeted for study so far. But such a small cross section makes it a unique probe for New Physics. Without the usual discrete $Z_2$ symmetry, the general two Higgs doublet model (g2HDM) can naturally raise the triple-top production to pb level. We illustrate how certain signal regions of four-top search can be utilized to constrain triple-top production, but urge a dedicated search. As an aside, we note that the CMS study at 13 TeV of scalar $t\bar t$ resonance interfering with QCD production background indicate some activity at 400 GeV. We comment that this could be explained in principle in g2HDM via the extra top Yukawa coupling.